Brake controller elevator system and a method for performing an emergency stop with
an elevator hoisting machine driven with a frequency converter
Field of the invention
The invention relates to controllers of a brake of an elevator.
Background of the invention
n an elevator system electromagnetic brakes are used as. inter alia holding brakes of
the hoisting machine and also as car brakes which brake the movement of the elevator
car by engaging with a vertical guide rail that is in the elevator hoistway.
The electromagnetic brake is opened by supplying current to the coil of the
electromagnet of the brake and connected by disconnecting the current supply of the
coil of the electromagnet of the brake.
Conventionally relays have been used for the current supply/disconnection of the
current supply, said relays being connected in series between a power source and the
coil of the electromagnet of the brake.
Connecting a relay causes a noise, which might disturb the residents of a building.
Relays are also large in size, owing to which their placement might be awkward,
especially in elevator systems that have no machine room. As mechanical components
relays also wear rapidly and they might fail when, among other things, the contacts
co ode or.when they weld closed.
Aim of the invention
One aim of the invention is to disclose a quieter brake control circuit, which also fits
into a smaller space. This aim can be achieved with a brake controller according to
claims 1 and 1. and also with an elevator system according to claim 16.
One aim of the invention is to disclose a solution that enables an emergency stop of an
elevator at a reduced deceleration in connection with a functional nonconformance.
such as an electricity outage. This aim can be achieved with a brake controller
according to claim 12. with an elevator system according to claim 6 . and with a
method according to claim 19.
The preferred embodiments of the invention are described in the dependent claims.
Some inventive embodiments and inventive combinations of the various embodiments
are also presented in the descriptive section and in the drawings of the present
application.
Summary of the invention
The brake controller according to the invention for controlling an electromagnetic
brake of an elevator comprises an input for connecting the brake controller to the DC
intermediate circuit of the frequency converter driving the hoisting machine of the
elevator, an output for connecting the brake controller to the electromagnet of the
brake a solid-state switch for supplying electric power from the DC intermediate
circuit of the frequency converter driving the hoisting machine of the elevator via the
output to the electromagnet of a brake and also a processor with which the operation
of the brake controller is controlled by producing control pulses in the control pole of
the switch of the brake controller.
The invention enables the integration of the brake controller into the DC intermediate
circuit of the frequency converter of the hoisting machine of the elevator. This is
advantageous because the combination of the frequency converter and the brake
controller is necessary from the viewpoint of the safe operation of the hoisting
machine of the elevator and. consequently from the viewpoint of the safe operation of
the whole elevator. n addition the size of the brake controller and also of the
frequency converter decreases, which enables space saving e.g. in an elevator system
having no machine room. The brake controller according to the invention can also be
connected as a part of the safety arrangement of an elevator via a safety signal, in
which case the safety arrangement of the elevator is simplified and it can be
implemented easily in many different ways. Additionally, the combination of the
safety signal and the brake switching logic according to the invention enables the
brake controller to be implemented completely without mechanical contactors, using
only solid-state components. When eliminating contactors also the disturbing noise
produced by the operation of the contactors is removed. Most preferably the input
circuit of the safety signal and the brake switching logic are implemented only with
discrete solid-state components, i.e. without integrated circuits In this case analysis of
the effect of different fault situations as well as of e.g. EMC interference connecting to
the input circuit of the safety signal from outside is facilitated, which also facilitates
connecting the brake controller to different elevator safety arrangements.
Since the brake controller can be connected to the DC intermediate circuit of the
frequency converter the energy returning to the DC intermediate circuit in connection
with motor braking of the elevator motor can be utilized in the brake control, which
improves the efficiency ratio of the elevator. n addition the main circuit of the brake
controller becomes simpler. In addition to this, connecting the brakes in connection
with an emergency stop caused by an electricity outage can be stepped by first
disconnecting the electricity supply to the electromagnet of only one brake and by
continuing the electricity supply to the electromagnets of the other brakes. This is
possible because there is electrical energy available in the DC intermediate circuit of
the frequency converter during an electricity outage, inter alia charged into the
capacitors of the DC intermediate circuit: in addition, as long as motor braking
continues, energy also returns to the intermediate circuit during an electricity outage.
In a preferred embodiment of the invention the brake controller comprises an input
circuit for a safety signal, which safety signal can be disconnected/connected from
outside the brake controller.
In a preferred embodiment of the invention the brake controller comprises brake
switching logic which is connected to the input circuit and is configured to prevent
passage of the control pulses to the control pole of the switch of the brake controller
when the safety signal is disconnected.
The supply of electric power to the control coil of the electromagnetic brake can
consequently be disconnected without mechanical contactors by preventing the
i
passage of control pulses to the control pole of the switch of the brake controller with
the brake switching logic according to the invention. The solid-state switch of the
brake controller can be e.g. a MOSFET or a silicon carbide tSiC) MOSFET transistor.
In a preferred embodiment of the invention the brake switching logic is configured to
allow passage of the control pulses to the control pole of the switch of the brake
controller when the safety signal is connected.
In a preferred embodiment of the invention the brake controller comprises indicator
logic for forming a signal permitting startup of a run. The indicator logic is configured
to activate, and on the other hand to disconnect the signal permitting startup of a run
on the basis of the status data of the brake switching logic.
In a preferred embodiment of the invention the signal path of the control pulses travels
to the control pole of the switch of the brake controller travels via the brake switching
logic, and the electricity supply to the brake switching logic is arranged via the signal
path of the safety signal.
By arranging the electricity supply to the brake switching logic via the signal path of
the safety signal it can be ensured that the electricity supply to the brake switching
logic disconnects and that the passage of control pulses to the control poles of the
switches of the brake controller consequently ceases, when the safety signal is
disconnected. In this case by disconnecting the safety signal, the power supply to the
control coil of the electromagnetic brake can be disconnected in a fail-safe manner
without separate mechanical contactors.
In a preferred embodiment of the invention the signal path of the control pulses from
the processor to the brake switching logic is arranged via an isolator. In this context an
isolator means a component that disconnects the passage of an electrical charge along
a signal path. In an isolator the signal is consequently transmitted e.g. as electromagnet
radiation (opto-isolator) or via a magnetic field or electrical field (digital isolator).
With the use of an isolator, the passage of charge carriers from the brake control
circuit to the brake switching logic is prevented e.g. when the brake control circuit
fails into a short-circuit.
In a preferred embodiment of the invention the brake switching logic comprises a
bipolar or multipolar signal switch, via which the control pulses travel to the control
pole of the switch of the brake controller. At least one pole of the signal switch is
connected to the input circuit in such a way that the signal path of the control pulses
through the signal switch breaks when the safety signal is disconnected.
In a preferred embodiment of the invention the electricity supply occurring via the
signal path of the safety signal is configured to be disconnected by disconnecting the
safety signal.
In a preferred embodiment of the invention the brake controller is implemented
without a single mechanical contactor.
n a preferred embodiment of the invention the brake controller comprises two outputs
to be controlled with a processor independently of each other via the first of which
outputs electric power is supplied from the DC intermediate circuit of the frequency
converter driving the hoisting machine of the elevator to the first electromagnet of a
brake and via the second output electric power is supplied from the DC intermediate
circuit of the frequency converter driving the hoisting machine of the elevator to a
second electromagnet.
In a preferred embodiment of the invention the brake controller comprises two
controllable switches, the first of which is configured to supply electric power to a first
electromagnet of a brake and the second is configured to supply electric power to a
second electromagnet of the brake. The processor is configured to control the
electricity supply to the first electromagnet by producing control pulses in the control
pole of the first switch and the processor is configured to control the electricity supply
to the second electromagnet by producing control pulses in the control pole of the
second switch.
n a preferred embodiment of the invention the processor comprises a communications
interface, via which the processor is connected to the elevator control. The brake
controller is configured to disconnect the electricity supply to the first electromagnet
but to continue the electricity supply from the DC intermediate circuit of the frequency
converter to the second electromagnet after it has received from the elevator control an
emergency stop request for starting an emergency stop to be performed at a reduced
deceleration.
n a preferred embodiment of the invention the brake controller is configured to
disconnect the electricity supply to the first and to the second electromagnet after it
has received from the elevator control a signal that the deceleration of the elevator car
is below a threshold value.
The invention also relates to a brake controller for controlling an electromagnetic
brake of an elevator. The brake controller comprises an input for connecting the brake
controller to a DC electricity source an output for connecting the brake controller to
the electromagnet of a brake, a transformer which comprises a primary circuit and a
secondary circuit, and also a rectifying bri dge which is connected between the
secondary circuit of the transformer and the output of the brake controller. The input
comprises a positive and a negative current conductor, and the brake controller
comprises a high-side switch and a low-side switch, which are connected in series
with each other between the aforementioned positive and aforementioned negative
current conductor, and also a processor, with which the electricity supply to the
electromagnet of the brake is controlled by producing control pulses in the control
poles of the high-side switch and low-side switch. The brake controller also comprises
two capacitors, which are connected in series with each other between the
aforementioned positive and aforementioned negative current conductor The primary
circuit of the transformer is connected between the connection point of the
aforementioned high-side switch and aforementioned low-side switch and the
connection point of the aforementioned capacitors. The aforementioned DC voltage
source to be connected to the input is most preferably the DC intermediate circuit of
the frequency converter driving the hoisting machine of the elevator. In the
aforementioned circuit the voltage of the capacitors reduces the voltage over the
primary circuit of the transformer, as a result of which the positive and negative
current conductor in the input of the brake controller can be connected to the highvoltage
DC intermediate circuit of the frequency converter without the special
requirements of the transformer increasing unreasonably. The voltage of the DC
intermediate circuit of the frequency converter is preferably approx. 500 V - 700 V. I
a preferred embodiment of the invention a separate choke is also connected between
the primary circuit of the transformer and the connection point of the high-side and
low-side switches. The choke reduces the current ripple of the transformer and
facilitates adjustment of the current.
The elevator system according to the invention comprises a brake controller according
to the description for controlling the brake of the hoisting machine of the elevator.
In a preferred embodiment of the invention the elevator system comprises a hoisting
machine an elevator car. a frequency converter with which the elevator car is driven
by supplying electric power to the hoisting machine, sensors configured to monitor the
safety of the elevator, and also an elevator control, which comprises an input for the
data of the aforementioned sensors. The elevator control is configured to form an
emergency stop request for starting an emergency stop to be performed at a reduced
deceleration, when the data received from the sensors indicates that the safety of the
elevator is endangered.
In a preferred embodiment of the invention the elevator system comprises an
acceleration sensor, which is connected to the elevator car. and the elevator control
comprises an input for the measuring data of the acceleration sensor. The elevator
control also comprises a memory in which is recorded a threshold value of the
deceleration of the elevator car. and the elevator control is configured to compare the
measuring data of the acceleration sensor to the threshold value for the deceleration of
the elevator car recorded in memory and also to form a signal that the deceleration of
the elevator car is below the threshold value.
In the method according to the invention for performing an emergency stop with an
elevator hoisting machine driven with a frequency converter one of the brakes of the
hoisting machine is connected by disconnecting the electricity supply to the
electromagnet of the aforementioned brake, but the other brakes of the hoisting
machine are still kept open by continuing the electricity supply from the DC
intermediate circuit of the frequency converter to the electromagnets of the
aforementioned other brakes of the hoisting machine.
In a preferred embodiment of the invention the deceleration during an emergency stop
of the elevator car is measured, and after a set period of time has passed also at least
one second brake of the hoisting machine is connected after the deceleration of the
elevator car is below a set threshold value.
The preceding summary, as well as the additional features and additional advantages
of the invention presented below, will be better understood by the aid of the following
description of some embodiments, said description not limiting the scope of
application of the invention.
Brief explanation of the figures
Fig. 1 presents as a block diagram an elevator system according to one
embodiment of the invention.
Fig. 2 presents as a circuit diagram a brake control circuit according to one
embodiment of the invention.
Fia. 3 presents as a circuit diagram a brake control circuit according to one
second embodiment of the invention.
Fig. 4 presents the circuit of the safety signal in the safety arrangement of an
elevator according to Fig. 3 .
Fig. 5 presents as a circuit diagram the fitting of a brake control circuit
according to the invention into connection with the safety circuit of an
elevator.
More detailed description of preferred embodiments of the invention
Fig. 1 presents as a block diagram an elevator system in which an elevator car (not in
figure) is driven in an elevator hoistway (not in figure) with the hoisting machine 6 of
the elevator via rope friction or belt friction. The speed of the elevator car is adjusted
to be according to the target value for the speed of the elevator car. i.e. the speed
reference calculated by the elevator control unit 35. The speed reference is formed in
such a way that passengers can be transferred from one floor to another with the
elevator car on the basis of elevator calls given by elevator passengers.
The elevator car is connected to the counterweight with ropes or with a belt traveling
via the traction sheave of the hoisting machine. Various roping solutions known in the
art can be used in an elevator sy stem, and they are not presented in more detail in this
context. The hoisting machine 6 also comprises an elevator motor, which is an electric
motor, with which the elevator car is driven by rotating the traction sheave, as well as
two electromagnetic brakes 9A. 9B. with which the traction sheave is braked and held
in its position.
Both electromagnetic brakes 9A. 9B of the hoisting machine comprise a frame part
fixed to the frame of the hoisting machine and also an armature part movably
supported on the frame part. The brake 9A. 9B comprises thinster springs which
resting on the frame part engage the brake by pressing the armature part onto the
braking surface on the shaft of the rotor of the hoisting machine or e.g. on the traction
sheave to brake the movement of the traction sheave. The frame part of the brake 9A.
9B comprises an electromagnet (i.e. a control coil ) which when energized exerts a
force of attraction between the frame part and the armature part. The brake is opened
b y supplying with the brake controller 7 current to the control coil of the brake, in
which case the force of attraction of the electromagnet pulls the armature part off the
braking surface and the braking force effect ceases. Correspondingly the brake is
connected by disconnecting the current supply to the control coil of the brake. With
the brake controller 7 the electromagnetic brakes 9A, 9B of the hoisting machine are
controlled independently of each other by supplying current separately to the control
The hoisting machine 6 is driven with the frequency converter 1. by supplying electric
power with the frequency converter 1 from the electricity network 25 to the electric
motor of the hoisting machine 6 . The frequency converter 1 comprises a rectifier 26.
with which the voltage of the AC network 25 is rectified for the DC intermediate
circuit 2A. 2B of the frequency converter. The DC intermediate circuit 2A. 2B
comprises one or more intermediate circuit capacitors 49. which function as temporary
stores of electrical energy. The DC voltage of the DC intermediate circuit 2A. 2B is
further converted by the motor bridge 3 into the variable-amplitude and variablefrequency
supply voltage of the electric motor.
During motor braking electric power also returns from the electric motor via the motor
bridge 3 back to the DC intermediate circuit 2A, 2B, from where it can be supplied
onwards back to the electricity network 25 with a rectifier 26. The power returning to
the DC intermediate circuit 2A. 2B during motor braking is also stored in an
intermediate circuit capacitor 49. During motor braking the force effect of the electric
motor 6 is in the opposite direction with respect to the direction of movement of the
elevator car. Consequently, motor braking occurs e.g. in an elevator with
counterweight when driving an empty elevator car upwards or when driving a fully
loaded elevator car downwards.
The elevator system according to Fig. 1 comprises mechanical normally-closed safety
switches 28. which are configured to supervise the position/locking of entrances to the
elevator hoistway as well as e.g. the operation of the overspeed governor of the
elevator car. The safety switches of the entrances of the elevator hoistway are
connected to each other in series. Opening of a safety switch 28 consequently indicates
an event affecting the safety of the elevator system such as the opening of an entrance
to the elevator hoistway. the arrival of the elevator car at an extreme limit switch for
permitted movement, activation of the overspeed governor, et cetera.
The elevator system comprises an electronic supervision unit 20. which is a special
microprocessor-controlled safety device fulfilling the EN LEC 61508 safety regulations
and designed to comply with S L 3 safety integrity level. The safety switches 28 are
wired to the electronic supervision unit 20. The electronic superv ision unit 20 is also
connected with a communications bus 30 to the frequency converter 1. to the elevator
control unit 35 and to the control unit of the elevator car. and the electronic
supervision unit 20 monitors the safety of the elevator system on the basis of data it
receives from the safety switches 28 and from the communications bus. The electronic
supervision unit 20 forms a safety signal 13. on the basis of which a run with the
elevator can be allowed or. on the other hand prevented by disconnecting the power
supply of the elevator motor 6 and by activating the machinery brakes 9A. 9B to brake
the movement of the traction sheave of the hoisting machine. Consequently the
electronic superv ision unit 20 prevents a run with the elevator e.g. when detecting that
an entrance to the elevator hoistway has opened, when detecting that an elevator car
has arrived at the extreme limit switch for pemiitted movement, and when detecting
that the overspeed governor has activated. In addition, the electronic supervision unit
receives the measuring data of a pulse encoder 27 from the frequency converter 1 via
the communications bus 30. and monitors the movement of the elevator car in
connection with, inter alia, an emergency stop on the basis of the measuring data of
the pulse encoder 27 it receives from the frequency converter . The frequency
converter 1 is provided with a safety logic 15. 16 to be connected to the signal path of
the safety signal 13. which safety logic disconnects the power supply of the elevator
motor and also connects the machinery brakes 9A. 9B.
The safety logic is formed from the drive prevention logic 15 and also from the brake
switching logic 16.
The circuit diagram of the main circuit of the brake switching logic 16 and of the
brake controller 7 is presented in more detail in Figs. 2 and 3 . For the sake of clarity
Figs. 2 and 3 present a circuit diagram in connection with only the one brake 9A. 9B.
because the circuit diagrams are similar in connection ith both brakes 9A. 9B. With
the DSP processor 11 of Figs. 2. 3. however, both brakes 9A. 9B are controlled.
In Figs. 2 and 3 the brake controller 7 is connected to the DC intermediate circuit 2A.
2B of the frequency converter 1. and the current supply to the control coils 10 of the
electromagnetic brakes 9A. 9B occurs from the DC intermediate circuit 2A. 2B.
The brake controller 7 of Fig. 2 comprises an input the positive current conductor
29A of which is connected to the positive busbar 2A of the DC intermediate circuit of
the frequency converter and the negative current conductor 29B is connected to the
negative busbar 2B of the DC intermediate circuit o f the frequency converter. The
output of the brake controller comprises a connector 4A. 4B. to which the supply
cables of the control coil 10 of the brake are connected. The brake controller 7
comprises a transformer 36. which comprises a primary circuit and a secondary circuit
as well as a rectifying bridge 37. which is connected between the secondary circuit of
the transformer and the output 4A. 4B of the brake controller. A high-side MOSFET
transistor 8A and also a lo side-MOSFET transistor 8B are connected between the
positive 29A and the negative 29B current conductor, which transistors are connected
in series with each other. A choke 47. which reduces the current ripple of the
transformer, is additionally connected between the pri mar circuit of the transformer
36 and the connection point 22 of the high-side and low-side MOSFET transistors 8A.
8B. Also between the aforementioned current conductors 29A, 29B are two capacitors
19A. 19B connected in series with each other. The primary circuit of the transformer
36 and the choke 47 are connected between the connection point 22 of the
aforementioned high-side MOSFET transistor 8A and aforementioned low-side
MOSFET transistor SB and the connection point 24 of the aforementioned capacitors
19A. 19B. Since the voltage of the connection point 24 of the capacitors is somewhere
between the voltages of the negative 2A and the positive 2B busbar of the DC
intermediate circuit of the frequency converter this type of circuit reduces the voltage
stress of the primary circuit of the transformer 36 and of the choke 47 connected in
series with the primary circuit. This is advantageous because the voltage between the
positive 2A and the negative 2B busbar of the DC intermediate circuit can be rather
high, up to approx. 800 volts or momentarily even higher. In some embodiments
silicon carbide (SiC) MOSFET transistors are used, instead of MOSFET transistors
8L. 8B. as the high-side 8L and low-side 8B switches. Being low-loss components,
silicon carbide (SiC) MOSFET transistors enable an increase in the current supply
capability of the brake controller 7 without the size of the brake controller 7 becoming
too large. n Fig. 2 there are parallel-connected flyback diodes connected in parallel
with the MOSFET transistors which diodes are most preferably Schottky diodes and
most preferably of all silicon carbide Schottky diodes.
The high-side 8A and the low-side 8B MOSFET transistors are connected alternately
by producing with the DSP processor 11 short preferably PWM modulated pulses in
the gates of the MOSFET transistors 8A. 8B. The switching frequency is preferably
approx. 100 kilohertz - 150 kilohertz. This type of high switching frequency enables
the size of the transformer 36 to be minimized. With the rectifier 37 in the secondary
circuit of the trans former 36 the secondary voltage of the transformer is rectified after
which the rectified voltage is supplied to the control coil 10 of the electromagnetic
brake. A current damping circuit 38 is also connected in parallel with the control coil
10 on the secondary side of the transformer which current damping circuit comprises
one or more components (e.g. a resistor capacitor, varistor. et cetera) which
receive! s) the energy stored in the inductance of the control coil of the brake in
connection with disconnection of the current of the control coil 0 . and consequently
accelerate(s) disconnection of the current of the control coil 10 and activation of the
brake 9 . Accelerated disconnection of the current occurs by opening the MOSFET
transistor 39 in the secondary circuit of the brake controller, in which case the current
of the coil 10 of the brake commutates to travel via the current damping circuit 38.
The brake controller to be implemented with the transformer described here is
particularly fail-safe especially from the viewpoint of earth faults, because the power
supply from the DC intermediate circuit 2A. 2B to both current conductors of the
control coil 10 of the brake disconnects when the modulation of the IGBT transistors
8A. 8B on the primary side of the transformer 36 ceases.
The brake controller 7 of Fig. 2 comprises brake switching logic 16. which is fitted to
the signal path between the DSP processor 1 and the control gates 8A. 8B of the
MOSFET transistors 8A. SB. Owing to the switching logic the current supply to the
1-i
control coil 10 of the brake can be disconnected safely without any mechanica]
contactors. The switching logic 16 comprises a digital isolator . which can be e.g.
one with an ADUM 4223 type marking manufactured by Analog Devices. The digital
isolator 1 receives its operating voltage for the secondary side 2 from a DC voltage
source 40 via the contact 14 of the safety relay, in which case the output of the digital
isolator 2 1 ceases modulating and the signal path from the DSP processor 1 to the
control gates of the MOSFET transistors 8A. 8B breaks when the contact 14 opens.
The circuit diagram of the brake switching logic 16 in Fig. 2 is. for the sake of
simplicity presented only in connection with the current path of the low-side
MOSFET transistor 8B. because the circuit diagram of the switching logic 16 is
similar also in connection with the current path of the high-side MOSFET transistors
8A.
Fig. 3 presents an alternative circuit diagram of the brake switching logic. The main
circuit of the brake controller 7 is similar to that in Fig. 2 . The digital isolator has.
however been replaced with a transistor 46, and the output of the DSP processor 1
has been taken directly to the base of the transistor 46. An MELF resistor 45 is
connected to the collector of the transistor 46. Elevator safety instruction EN 8 1-20
specifies that failure of an MELF resistor into a short-circuit does not need to be taken
into account v hen making a fault analysis, so that by selecting the value of the MELF
resistor to be sufficiently large a signal path from the output of the brake control
circuit 11 to the gate of a MOSFET transistor 8A. SB can be safely prevented when
the safety contact 14 is open. Also the brake switching logic 16 comprises a PNP
transistor 23. the emitter of which is connected to the input circuit 2 of the safety
signal 3 . Consequently the electricity supply from the DC voltage source 40 to the
emitter of the PNP transistor 23 of the brake switching logic 6 disconnects, when the
contact 14 of the safety relay of the electronic supervision unit 20 opens. At the same
time the signal path of the control pulses from the brake control circuit 1 to the
control gates of the MOSFET transistors 8A. 8B of the brake controller 7 is
disconnected in which case the MOSFET transistors 8A. 8B open and the power
supply from the DC intermediate circuit 2A. 2B to the coil 0 of the brake ceases. The
circuit diagram of the brake switching logic 16 in Fig. 3 is. for the sake of simplicity,
presented only in respect of the MOSFET transistor 8B connecting to the low-voltage
busbar 2B of the DC intermediate circuit, because the circuit diagram of the brake
switching logic 16 is similar also in connection with the MOSFET transistor 8A
connecting to the high-voltage busbar 2A of the DC intermediate circuit. With the
solution of Fig. 3 a simple and cheap switching logic 16 is achieved.
Power supply from the DC intermediate circuit 2A. 2B to the coil 10 of the brake is
again allowed by controlling the contact of the safety relay 14 closed, in which case
DC voltage is connected from the DC voltage source 40 to the emitter of the P P
transistor 23 of the brake switching logic 16.
As already stated in the preceding the brake controller 7 of Fig. 1 (and also of Figs. 2
and 3) comprises separate but similar main circuits for the current supply of the
control coils 10 of the first 9A and second 9B machinery brake. The MOSFET
transistors 8A. 8B in the first main circuit supply electric power to the electromagnet
0 of the first machinery brake 9A and the MOSFET transistors 8A. 8B of the second
main circuit supply electric power to the electromagnet of the second machinery brake
9A. The MOSFET transistors 8A. SB of both main circuits are controlled with the
same processor 11. in which case the current supply to the control coils 10 of the first
brake 9A and of the second brake 9B can be controlled with the same processor 1
independently of each other. The processor 1 comprises a bus controller, via which
the processor is connected to the same serial interface bus as the elevator control
unit 35 and as the electronic supervision unit 20. (20. 35). The DSP processor 11 is
configured to disconnect the electricity supply to the control coil 0 of the first
machinery brake 9A but to continue the electricity supply from the DC intermediate
circuit 2A. 2B of the frequency converter to the control coil 10 of the second
machinery brake 9B after it has received from the elevator control unit 35 via the
serial interface bus an emergency stop request for starting an emergency stop to be
performed at a reduced deceleration. The DSP processor 11 is further configured to
disconnect the electricity supply to the control coil of also the second machinery brake
9B after it has received a sisnal from the elevator control unit 35 via the serial
interface bus that the deceleration of the elevator car is below a threshold value. The
deceleration of the elevator car can be measured e.g. with an acceleration sensor
connected to the elevator car or by measuring the deceleration of the traction sheave of
the hoisting machine, and thereby of the elevator car. with an encoder fitted to the
shaft of the hoisting machine.
This means that the elevator system of Fig. 1 together with the brake controller of Fig.
2 or 3 enables an emergency braking method, wherein the hoisting machine 6 of the
elevator, and thus the elevator car. are braked at a reduced deceleration e.g. during an
electricity outage. The use of reduced deceleration is advantageous e.g. in the types of
elevator systems in which the friction between the traction sheave of the hoisting
machine and the rope is high. High friction can be caused by the ropes not being able
to slip on the traction sheave during an emergency stop when the deceleration of the
elevator car might otherw ise increase to be unnecessarily high from the viewpoint of a
passenger in the elevator car. High friction between a traction sheave and a rope can
result e.g. from a coating of the traction sheave and/or of the rope: e.g. the friction
between a coated belt and a traction sheave is usually high: in addition friction is high
(absolute) when using a toothed belt, which travels in grooves made in the traction
sheave.
In the emergency braking method one 9A of the brakes of the hoisting machine is
connected by disconnecting the electricity supply to the electromagnet 10 of the
aforementioned brake, but the other brake 9B is still kept open by continuing the
electricity supply from the DC intermediate circuit 2A. 2B of the frequency converter
to the electromagnet 10 of the aforementioned other brake 9B. At the same time the
deceleration during an emergency stop of the elevator car is measured, and after a set
amount of time has passed also the aforementioned second brake 9B is connected by
disconnecting the electricity supply to the electromagnet 0 of the second brake 9B.
after the deceleration of the elevator car is below a set threshold value.
The frequency converter 1 of Fig. 1 also comprises indicator logic 17. which forms
data about the operating state of the drive prevention logic 15 and of the brake
switching logic 16 for the electronic supervision unit 20. Fig. 4 presents how the safety
functions of the aforementioned electronic supervision unit 20 and of the frequency
converter 1 are connected together into a safety circuit of the elevator. According to
Fig. 4 the safety signal 13 is conducted from the DC voltage source 40 of the
frequency converter 1 via the contacts 14 of the safety relay of the electronic
supervision unit 20 and onwaids back to the frequency converter 1. to the input circuit
12 of the safety signal. The input circuit 12 is connected to the drive prevention logic
5 and also to the brake switching logic 16 via the diodes 4 1. The purpose of the
diodes 4 is to prevent voltage supply from the drive prevention logic 5 to the brake
switching logic 16/from the brake switching logic 16 to the drive prevention logic 15
as a consequence of a failure, such as a short-circuit et cetera occurring in the drive
prevention logic 1 or in the brake switching logic 16.
The frequency converter of Fig. 1 comprises indicator logic, which forms data about
the operating state of the drive prevention logic 15 and of the brake switching logic 16
for the electronic supervision unit 20. The indicator logic 7 is implemented as AND
logic, the inputs of which are inverted. A signal allowing startup of a run is obtained
as the output of the indicator logic, which signal reports that the drive prevention logic
15 and the brake switching logic are in operational condition and starting of the next
run is consequently allowed. For activating the signal 8 allowing the startup of a run
the electronic supervision unit 20 disconnects the safety signal 13 by opening the
contacts 14 of the safety relay in which case the electricity supply of the drive
prevention logic 15 and of the brake switching logic 16 must go to zero. The indicator
logic is described in Fig. 4 .
Fig. 5 presents an embodiment of the invention in which the safety logic of the
frequency converter 1 is fitted into an elevator having a conventional safety circuit 34.
The safety circuit 34 is formed from safety switches 28. such as e.g. safety switches of
the doors of entrances to the elevator hoistvvay. that are connected together in series.
The coil of the safety relay 44 is connected in series with the safety circuit 34. The
contact of the safety relay 44 opens, when the current supply to the coil ceases as the
safety switch 28 of the safety circuit 34 opens. Consequently the contact of the safety
relay 44 opens e.g. when a serviceman opens the door of an entrance to the elevator
hoistway with a service key. The contact of the safety relay 44 is wired from the DC
voltage source 40 of the frequency converter 1 to the brake switching logic 16 in such
a way that the electricity supply to the brake switching logic ceases when the contact
of the safety relay 44 opens. Consequently when the safety switch 28 opens also the
passage of control pulses to the IGBT transistors 8A. SB of the brake controller 7
ceases, and the brakes 9 of the hoisting machine activate to brake the movement of the
traction sheave of the hoisting machine.
It is obvious to the person skilled in the art that, differing from what is described
above, the electronic supervision unit 20 can also be integrated into the brake
controller 7. preferably on the same circuit card as the brake switching logic 16. In this
case the electronic supervision unit 20 and the brake switching logic 16 form,
however subassemblies that are clearly distinguishable from each other, so that the
fail-safe apparatus architecture according to the invention is not fragmented.
It is further obvious to the person skilled in the art that that the brake controller 7
described above is suited to controlling also a car brake, in addition to a machinery
brake 9A. 9B of the hoisting machine of an elevator, without mechanical contactors.
The invention is described above by the aid of a few examples of its embodiment. It is
obvious to the person skilled in the ail that the invention is not only limited to the
embodiments described above, but that many other applications are possible within the
scope of the inventive concept defined by the claims.
Claims
1. Brake controller (7 ) for controlling the electromagnetic brake (9A. 9B) of an
elevator, which brake controller (7) comprises:
an input (29A. 29B) for connecting the brake controller to the DC intermediate
circuit (2A. 2B) of the frequency converter driving the hoisting machine of the
elevator;
an output 4A. 4B) for connecting the brake controller (7) to an electromagnet ( 10)
of the brake:
a solid-state switch (8A. 8B) for supplying electric power from the DC intennediate
circuit <2A, 2B ) of the frequency converter driving the hoisting machine of the
elevator via the output (4A. 4B) to the electromagnet (10) of a brake (9A, 9B); and
also
a processor ( ), with which the operation of the brake controller (7) is controlled
by producing control pulses in the control pole of the switch (8 . 8B) of the brake
controller.
2 . Brake controller according to claim 1. c h a r a c t e r i z e d in that the brake
controller (7) comprises an input circuit ( 12) for a safety signal ( 13), which safety
signal 1 ) can be disconnected/connected from outside the brake controller (7).
3 . Brake controller according to claim 2. c h a r a c t e r i z e d in that the brake
controller (7) comprises brake switching logic ( 16). which is connected to the input
circuit 12 ) and is contigured to prevent passage of the control pulses to the control
pole of the switch (8A. 8B) of the brake controller when the safety signal ( 13) is
disconnected.
4 . Brake controller according to claim 3. c h a r e r i z e d in that the brake
switching logic ( 16) is configured to allo passage of the control pulses to the control
pole of the switch (8A. 8B of the brake controller when the safety signal ( 13 ) is
connected.
5 . Brake controller according to claim 3 or 4, c a r a c t e r e in that the brake
controller (7) comprises indicator logic ( 17) for forming a signal ( 18) permitting
startup of a run.
and in that the indicator logic ( 7) is configured to activate and on the other hand
to disconnect the signal (18) permitting startup of a run on the basis of the status data
of the brake switching logic 16).
6 . Brake controller according to any of claims 3 - 5. c h a r a c t e r z e d in that the
signal path of the control pulses travels to the control pole of the switch (8A. 8B ) of
the brake controller via the brake switching logic ( 16):
and in that the electricity supply to the brake switching logic ( 16) is arranged via
the signal path of the safety signal ( 13).
7 . Brake controller according to any of claims 3 - 6. c h a c e r e in that the
signal path of the control pulses from the processor ( 11) to the brake switching logic
( 6 ) is arranged via an isolator (22 ) .
8 . Brake controller according to any of claims 3 - 7. c h a r a c t e r i z e d in that the
brake switching logic ( 16) comprises a bipolar or multipolar signal switch (24). via
which the control pulses travel to the control pole of the s itch (8A. 8B) of the brake
controller:
and in that at least one pole of the signal switch (24) is connected to the input
circuit ( 12) in such a way that the signal path of the control pulses through the signal
switch (24) breaks when the safety signal (13) is disconnected.
9 . Brake controller according to any of claims 6 - 8. c h a rac t e r i z e d in that the
electricity supply occurring via the signal path of the safety signal ( 13) is configured to
be disconnected by disconnecting the safety signal (13 ) .
10. Brake controller according to any of claims 3 - 9. c h a a c t e r i z e d in that the
brake controller (7 ) is implemented without any mechanical contactors.
11. Brake controller (7) for controlling the electromagnetic brake (9A. 9B) of an
elevator, comprising:
an input (29 . 29B) tor connecting the brake controller (7) to the DC electricity
source (2A. 2B)
an output (4A. 4B) for connecting the brake controller (7) to the electromagnet
( 10) of the brake:
a transformer (36). which comprises a primary circuit and a secondary circuit:
a rectifying bridge (37). which is connected between the secondary circuit of the
transformer and the output (4A. 4B) of the brake controller:
c h a r a c t e r i z e d in that the input comprises a positive (29A) and a negative
(29B) current conductor:
and in that the brake controller (7) comprises:
a high-side switch (8A ) and also a low-side switch (8B). which are connected in
series with each other between the aforementioned positive (29A) and aforementioned
negative (29B) current conductor;
a processor ( 11). with which the electricity supply to the electromagnet (10) of the
brake is controlled by producing control pulses in the control poles of the high-side
switch (8A) and low-side switch (SB);
two capacitors <19A. 19B). which are connected in series with each other between
the aforementioned positive (29A) and the aforementioned negative (29B ) current
conductors:
and in that the primary circuit of the transformer is connected between the
connection point (22) of the aforementioned high-side switch (8A) and
aforementioned low-side switch (8B) and the connection point (24) of the
aforementioned capacitors 19A. 19B ).
12. Brake controller according to any of the preceding claims, c h a rac t e r i z e d in
that the brake controller (7) comprises two outputs (4A. 4B) to be controlled with a
processor ( 1) independently of each other, via the first output of which electric power
is supplied from the DC intermediate circuit (2A. 2B ) of the frequency converter ( )
driving the hoisting machine (6) of the elevator to the first electromagnet ( 10) of a
brake and via the second output electric power is supplied from the DC intermediate
circuit (2A. 2B) of the frequency converter ( 1) driving the hoisting machine (6) of the
elevator to the second electromagnet ( 10).
13. Brake controller according to claim 12, h c t e r i z e d in that the brake
controller comprises two controllable switches, the first of which is configured to
supply electric power to a first electromagnet ( 10) of a brake and the second is
configured to supply electric power to a second electromagnet of the brake;
and in that the processor ( is configured to control the electricity supply to the
first electromagnet by producing control pulses in the control pole of the first switch;
and in that the processor (11) is configured to control the electricity supply to the
second electromagnet by producing control pulses in the control pole of the second
switch.
14. Brake controller according to claim 12 or 13. c h a a c e i z e d in that the
processor ( ) comprises a communications interface, via which the processor ( ) is
connected to the elevator control (20. 35 );
and in that the brake controller (7) is configured to disconnect the electricity
supply to the first electromagnet ( 10) but to continue the electricity supply from the
DC intermediate circuit (2A. 2B) of the frequency converter to the second
electromagnet ( 10) after it has received from the elevator control (20. 35) an
emergency stop request for starting an emergency stop to be performed at a reduced
deceleration.
5 . Brake controller according to claim 14. h a rac t r i e in that the brake
controller (7) is configured to disconnect the electricity supply to the first and to the
second electromagnet after it has received from the elevator control (20. 35) a signal
that the deceleration of the elevator car is below a threshold value.
16. Elevator system, c h a rac t e r i z e d in that the elevator system comprises a brake
controller (7) according to any of claims 1 - 15 for controlling the brake <9A. 9B) of
the hoisting machine of an elevator.
17. Elevator system according to claim 16. c h a r c t e r i z e d in that the elevator
system comprises:
a hoisting machine (6):
an elevator car:
a frequency converter ( 1). with which the elevator car is driven by supplying
electric power to the hoisting machine (6):
sensors (28) configured to monitor the safety of the elevator;
an elevator control (20. 35). which comprises an input for the data of the
aforementioned sensors (28):
and in that the elevator control (20. 35) is configured to form an emergency stop
request for starting an emergency stop to be performed at a reduced deceleration, when
the data received from the sensors (28) indicates that the safety of the elevator is
endangered.
18. Elevator system according to claim 17. c h a r a c t e r i z e d in that the elevator
system comprises an acceleration sensor which is connected to the elevator car;
and in that the elevator control (20. 35) comprises an input for the measuring data
of the acceleration sensor;
and in that the elevator control (20. 35) comprises a memory in which is recorded
a threshold value of the deceleration of the elevator car;
and in that the elevator control (20. 35 ) is configured to compare the measuring
data of the acceleration sensor to the threshold value for the deceleration of the
elevator car recorded in memory :
and in that the elevator control (20. 35) is configured to form a signal that the
deceleration of the elevator car is below the threshold value.
19. Method for performing an emergency stop with an elevator hoisting machine (6)
driven with a frequency converter ( ). in which method:
one of the brakes (9A. 9B) of the hoisting machine is connected by
disconnecting the electricity supply to the electromagnet ( 10) of the
aforementioned brake, but
h a r a c t e r i z e d in that:
- the other brakes 9A. 9B) of the hoisting machine are still kept open by
continuing the electricity supply from the DC inteiTnediate circuit (2A.
2B) of the frequency converter to the electromagnets ( 10) of the
aforementioned other brakes (9A. 9B) of the hoisting machine.
0 . Method according to claim 19. c h a c t e r i z e d in that:
the deceleration during an emergency stop of the elevator car is
measured, and
and after a set period of time has passed also at least one second brake
(9A. 9B) of the hoisting machine is connected after the deceleration of
the elevator car is below a set threshold value.