ADJUSTMENT DEVICE AND AN ELECTRIC DRIVE OF AN ELEVATOR
Field of the invention
The invention relates to devices and methods for controlling the operation of the electric
drive of an elevator.
Background of the invention
The source voltage produced by the rotor excitation of an elevator motor depends on the
speed of rotation of the rotor. When the speed of rotation of the rotor and thereby the
source voltage increases, the magnitude of the needed supply voltage of the motor also
increases. The magnitude of the needed supply voltage of the motor is also affected by
e.g. the motor current. Since the largest possible supply voltage of the motor is
determined on the basis of the maximum output voltage of the power supply apparatus,
such as of the frequency converter, of the motor, the permitted speed range of the motor
must be limited such that the supply voltage required by the motor does not exceed the
maximum output voltage of the power supply apparatus of the motor. Particularly in
lower-powered systems, a frequency converter is usually used as the power supply
apparatus of the motor, the intermediate circuit voltage of which frequency converter is
unregulated and is determined directly on the basis of the voltage of the electricity
network supplying the frequency converter. Since the intermediate circuit voltage, on
the other hand, sets the largest possible output voltage of the frequency converter, e.g. a
momentary voltage reduction occurring in the electricity network supplying the
frequency converter has the effect that the output voltage of the frequency converter
decreases. For this reason the rated speed of the elevator and the corresponding
maximum speed of rotation of the electric motor during normal operation are usually
selected such that at the rated speed and with the rated load a voltage margin remains
between the output voltage of the frequency converter and the supply voltage of the
motor, which margin allows e.g. a 15 per cent voltage reduction in the voltage of the
electricity network supplying the frequency converter. A voltage reduction in the
electricity network supplying the frequency converter can be caused e.g. by a voltage
reduction or electricity outage occurring in the public electricity network. Also, e.g. in
connection with acceleration of the elevator, the large instantaneous current taken by the
electric motor might cause a momentary voltage reduction in the supplying electricity
network. The voltage endurance of the solid-state switches of the power supply
apparatus of the motor also limits the maximum output voltage in those power supply
apparatuses in which the intermediate circuit voltage can be regulated.
Since the speed of the elevator affects e.g. the transport capacity of the elevator system
as well as the door-to-door time, within the framework of which a passenger can be
moved from the departure floor to the destination floor, it would be advantageous to
select the speed of rotation of the elevator motor to be as close as possible to the value
set by the maximum output voltage of the power supply apparatus. In this case when the
speed of rotation is increased, however, a problem forms in that repetitive voltage
reductions/electricity outages might cause unnecessarily many breaks in the operation
of the elevator.
In some cases it would be advantageous to increase the speed of the elevator car to be
even higher than the rated speed in situations in which the net load of the elevator, i.e.
the force difference acting in the elevator ropes on opposite sides of the traction sheave,
is smaller than the rated load. Also in this case operating breaks of the elevator caused
by voltage reductions/electricity outages might form a problem.
Summary of the invention
The aim of the invention is to disclose an adjustment device for regulating the operation
of the electric drive of an elevator, using which device it is possible to drive the elevator
with the electric drive of the elevator closer to the upper limit set by the maximum
output voltage of the power supply apparatus of the motor than in prior art such that a
run with the elevator continues also during a momentary voltage reduction of the
electricity network supplying the power supply apparatus of the motor. To achieve this
aim the invention discloses an adjustment device according to claim 1, an electric drive
according to claim 14, and also a method according to claim 18 for controlling the
electric drive of an elevator. The preferred embodiments of the invention are described
in the non-independent claims.
With regard to the first aspect, the invention relates to an adjustment device in
connection with an electric drive of an elevator. The electric drive of the elevator
comprises an electric motor. The electric drive of the elevator further comprises a power
supply apparatus of the electric motor for adjusting the supply voltage of the electric
motor. The adjustment device according to the invention comprises means for
controlling the power supply apparatus of the electric motor as well as a speed regulator
for adjusting the speed of the electric motor. The adjustment device is arranged to
determine the output voltage of the power supply apparatus of the electric motor in
relation to the permitted maximum value of the output voltage, and the adjustment
device is arranged to interrupt the operation of the speed regulator but to continue the
operation of the power supply apparatus of the electric motor when the output voltage
of the power supply apparatus of the electric motor reaches the permitted maximum
value.
In a preferred embodiment of the invention the adjustment device is arranged to
continue the interrupted operation of the speed regulator when the difference between
the output voltage of the power supply apparatus of the electric motor and the permitted
maximum value of the output voltage returns to be at least the magnitude of the required
limit value.
In a preferred embodiment of the invention the power supply apparatus of the electric
motor comprises a motor bridge, which comprises controllable solid-state switches,
which are switched in response to the voltage reference of the motor bridge. The
adjustment device is arranged to determine the output voltage of the power supply
apparatus of the electric motor in relation to the permitted maximum value of the output
voltage preferably on the basis of the voltage reference of the motor bridge of the power
supply apparatus of the electric motor. The adjustment device is in this case arranged to
preferably interrupt the operation of the speed regulator but to continue the operation of
the power supply apparatus of the electric motor when the voltage reference of the
motor bridge of the power supply apparatus of the electric motor reaches the permitted
maximum value. In a preferred embodiment of the invention the adjustment device is
arranged, after the operation of the speed regulator has been interrupted, to limit the
length of the phasor of the voltage reference vector of the motor bridge of the power
supply apparatus of the electric motor to the value for the length of the phasor set by the
permitted maximum value of the voltage reference of the motor bridge of the power
supply apparatus of the electric motor. The adjustment device is further preferably
arranged to continue the interrupted operation of the speed regulator when the
difference between t e voltage reference of the motor bridge of the power supply
apparatus of the electric motor and the permitted maximum value of the voltage
reference returns to be at least the magnitude of the required limit value. The
aforementioned permitted maximum value of the voltage reference is preferably
determined on the basis of the maximum value of the modulator comparator of the
adjustment device.
In a preferred embodiment of the invention the speed regulator is arranged to adjust the
speed of the electric motor towards the value of the speed reference, and the adjustment
device is arranged to set the initial value of the speed reference to correspond to the
speed of the electric motor when the interrupted operation of the speed regulator
continues.
In a preferred embodiment of the invention the adjustment device is arranged to keep
the value of at least one adjustment parameter of the power supply apparatus of the
electric motor constant after the operation of the speed regulator has been interrupted.
The aforementioned adjustment parameter of the power supply apparatus of the electric
motor to be held constant can be e.g. the current reference of the voltage regulator of the
adjustment device and/or the voltage reference of the voltage regulator of the
adjustment device.
In one embodiment of the invention the adjustment device is arranged to set the
aformentioned adjustment parameter of the power supply apparatus of the electric
motor, which parameter is to be Jield constant after the operation of the speed regulator
has been interrupted, to correspond to the value of the adjustment parameter in question
when the operation of the speed regulator is interrupted.
In one embodiment of the invention the adjustment device is arranged to adjust the
current of the electric motor towards the value of the current reference for adjusting the
torque of the electric motor.
With regard to the second aspect, the invention relates to an electric drive of an elevator,
which electric drive comprises a hoisting machine, which hoisting machine comprises
an electric motor. The electric drive of the elevator also comprises a power supply
apparatus of the electric motor as well as an adjustment device of the type disclosed
above for controlling the electric drive of the elevator. The electric drive of the elevator
is arranged to continue the current supply occurring to the electric motor with the power
supply apparatus of the electric motor when the output voltage of the power supply
apparatus of the electric motor reaches the permitted maximum value.
The power supply apparatus of the electric motor according to the invention is
preferably a frequency converter and the electric motor according to the invention is
preferably a permanent-magnet synchronous motor.
In a preferred embodiment of the invention the adjustment device is arranged to
interrupt the speed regulator but to continue the current supply to the stator of the
electric motor when the output voltage of the power supply apparatus of the electric
motor reaches the permitted maximum value.
In the method according to the invention for controlling the electric drive of an elevator:
the output voltage of the power supply apparatus of the electric motor in relation to the
permitted maximum value of the output voltage is determined, and also the operation of
the speed regulator is interrupted but the operation of the power supply apparatus of the
electric motor is continued when the output voltage of the power supply apparatus
reaches the permitted maximum value.
The invention enables a run with the elevator to be continued despite a voltage
reduction or electricity outage occurring in the supplying electricity network. In this
case the speed of the electric motor of the hoisting machine of the elevator, and thereby
of the elevator car, can also be increased to be closer to the maximum value of speed set
by the output voltage of the power supply apparatus of the electric motor than in prior
art.
The aforementioned summary, as well as the additional features and 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 an elevator system according to the invention, as a block diagram
Fig. 2 presents an adjustment device according to the invention, as a functional
diagram
Fig. 3 illustrates the operation of a pulse width modulator
Fig. 4 presents the operation according to a first embodiment of the invention of
an electric drive of an elevator according to the invention in connection
with a voltage reduction of the electricity network supplying the power
supply apparatus of the motor
Fig. 5 presents a motor bridge of a frequency converter according to the
invention
Fig. 6 presents the operation according to a second embodiment of the invention
of an electric drive of an elevator according to the invention in connection
with a voltage reduction of the electricity network supplying the power
supply apparatus of the motor
More detailed description of preferred embodiments of the invention
Fig. 1 presents an elevator system, which comprises an electric drive 2 for moving the
elevator car 23 in the elevator hoistway 24 according to the speed reference formed by
the elevator control unit 25. The electric drive 2 comprises a hoisting machine 22,
which comprises an alternating current motor 3 as the power producing part.
Additionally, the electric drive 2 comprises a frequency converter 4 for supplying
variable-amplitude and variable-frequency output voltage to the alternating current
motor 3.
The elevator car 23 is suspended in the elevator hoistway 24 with ropes, a belt or
corresponding passing via the traction sheave of the hoisting machine 22. The hoisting
machine 22 is, in this embodiment of the invention, fixed to the guide rail (not in figure)
of the elevator car, in a space between the guide rail and the wall of the elevator
hoistway 24. The hoisting machine 22 could, however, also be fixed e.g. to a special
machine bedplate, and the hoisting machine could also be disposed in a machine room
instead of in the elevator hoistway.
The frequency converter 4 comprises an adjustment device 1 for controlling the electric
drive 2 of the elevator. The adjustment device 1 is fitted in connection with the control
grids of the controllable IGBT transistors of the motor bridge of the frequency converter
4 and the adjustment device 1 comprises means for controlling the power supply
apparatus 4 of the electric motor by switching the IGBT transistors of the motor bridge
with switching pulses, the frequency of which is essentially higher than the frequency of
the fundamental frequency of the output voltage of the frequency converter.
The adjustment device 1 also comprises a speed regulator, by means of which the speed
of the electric motor 3 and thus also of the elevator car 23 is adjusted towards the speed
reference formed by the elevator control unit 25. The speed reference is sent to the
speed regulator via a data transfer bus between the frequency converter 4 and the
elevator control unit 25. The frequency converter 4 also comprises an input for the
measuring signal of the speed of rotation of the rotor of the electric motor 3. The speed
of rotation of the rotor is measured with a pulse encoder 26 to be connected to the
traction sheave of the hoisting machine 22.
Fig. 2 describes in more detail the operation of an adjustment device 1 suited to be used
e.g. in the embodiment of Fig. 1. The adjustment device 1 is arranged to determine the
output voltage 9 of the power supply apparatus of the electric motor in relation to the
permitted maximum value of the output voltage. The adjustment device 1 is arranged to
interrupt the operation of the speed regulator 8 but to continue the run with the elevator
by supplying current with the frequency converter 4 to the stator of the electric motor 3
when the output voltage 9 of the frequency converter 4 reaches the permitted maximum
value 10. Additionally, the adjustment device 1 is further arranged to continue the
interrupted operation of the speed regulator 8 when the difference 15 between the output
voltage 9 of the power supply apparatus of the electric motor and the permitted
maximum value of the output voltage returns to be at least the magnitude of the required
limit value. The speed regulator 1 is arranged to set the initial value of the speed
reference 18 to correspond to the speed 19 of the electric motor, when the interrupted
operation of the speed regulator continues.
The adjustment device 1 comprises a cascade regulator, which comprises a current
regulator 5 in addition to a speed regulator 8. The speed regulator 8 compares with the
pulse encoder 26 the measured speed 19 of the electric motor 3 to the speed reference
18 formed by the elevator control unit 25 and also calculates, on the basis of the
comparison, the torque reference 20 in response to which the torque of the electric
motor 3 is adjusted such that the speed 19 of the electric motor approaches the speed
reference 18. The speed reference could also be formed directly in the adjustment
device 1, instead of the elevator control unit 25, using the computing capacity of the
frequency converter 4 in the calculation of the speed reference 18. The torque of the
electric motor 3 is here directly proportional to the stator current of the electric motor 3,
so that the torque reference 20 is used as a current reference of the current regulator 5.
The current regulator 5 adjusts the stator current 2 1 in an auxiliary d,q coordinate
system rotating along with the rotor of the electric motor, in which system the d axis is
in the direction of the excitation axis of the electric motor and the q axis is in the
direction of the torque axis of the electric motor. The current reference 20 therefore
forms a reference for the stator current in the direction of the q axis.
The voltage reference 12 is obtained as the output of the current regulator 5 for the
motor bridge of the frequency converter 4. One possible motor bridge 16 of the
frequency converter 4 is presented in Fig. 5. The voltage reference 12 is first converted
from the d,q coordinate system into the three-phase stator coordinate system in
conversion block 27, and the three-phase voltage references 17 of the motor bridge of
the frequency converter 4 that are converted into the stator coordinate system are taken
to the pulse-width modulator 6, by means of which switching references are formed for
the IGBT transistors of the motor bridge of the frequency converter 4. The operation of
one such possible pulse width modulator 6 is presented in Fig. 3 in respect of one phase.
The pulse width modulator 6 comprises a modulator comparator, which compares for
each specific phase the value of the three-phase voltage references 17 of the motor
bridge of the frequency converter 4 to the value of the saw-tooth generator of the
modulator comparator. When the value of the phase voltage reference 17 is greater than
or equal to the value of the saw-tooth generator, the modulator comparator forms a
value 1 of the switching reference 11 for the IGBT transistors 30, 3 1 of the phase in
question of the motor bridge of the frequency converter, according to which value 1 the
IGBT transistor 30 of the top branch is controlled into a conductive state and the current
flow through the IGBT transistor 31 of the bottom branch is disconnected. In this case
the instantaneous output voltage 9 of the frequency converter corresponds to the
positive voltage 32 of the DC intermediate circuit. When the value of the phase voltage
reference 17, on the other hand, falls below the value of the saw-tooth generator, the
modulator comparator forms a value 0 of the switching reference 11 for the IGBT
transistors 30, 3 1 of the phase in question of the motor bridge of the frequency
converter, according to which value 0 the current flow through the IGBT transistor 30
of the top branch is disconnected and the IGBT transistor 3 1 of the bottom branch is
controlled into a conductive state. In this case the instantaneous output voltage 9 of the
frequency converter corresponds to the negative voltage 33 of the DC intermediate
circuit. On the basis of what is presented above, it can be observed that the maximum
value 10 of the saw-tooth generator determines the permitted maximum value of the
voltage reference 17 of the motor bridge and thereby also the permitted maximum value
of the output voltage 9 of the power supply apparatus, because when the absolute value
of the voltage reference of the motor bridge exceeds the maximum value 10 of the saw¬
tooth generator the modulator comparator becomes saturated and the IGBT transistors
30, 31 of the motor bridge no longer switch at the switching frequency set by the saw¬
tooth generator. When the modulator comparator becomes saturated, also the output
voltage 9 of the motor bridge of the frequency converter distorts, which would cause
vibration in the electric motor 3. To avoid this problem the length of the phasor of the
voltage reference vector of the motor bridge is limited to the value of the length of the
phasor set by the maximum value 10 of the saw-tooth generator in operating block 34.
In practice this is done by determining the length |U| of the phasor of the voltage
reference 12 in the auxiliary d;q coordinate system U< j , Uq from the equation:
\u\ = +u
and also by determining that the value of the length |U| of the phasor never exceeds the
aforementioned maximum value 10 of the saw-tooth generator. In a preferred
embodiment of the invention this is done by limiting only the voltage reference
component Uq in the direction of the torque axis q and by letting the voltage reference
component U in the direction of the excitation axis change freely, in which case the
phasor of the voltage reference is able to rotate.
The software of the adjustment device 1 comprises a control part 28, which reads the
value of the voltage reference 12 of the motor bridge of the frequency converter 4 and
interrupts the operation of the speed regulator 8 if the value of the voltage reference 12
of the motor bridge reaches or exceeds the maximum value 10 according to the saw¬
tooth generator of the modulator comparator. In a first preferred embodiment of the
invention the operation of the current regulator 5 continues despite the interruption of
the operation of the speed regulator. In this case when the operation of the speed
regulator is interrupted the control part 28 sets for the current reference 20 of the current
regulator 5 the value that current reference has at the moment of interruption of the
operation of the speed regulator 8. The value 20 of the current reference is kept constant
after interruption of the operation of the speed regulator 8. In this case the run with the
elevator continues without the speed regulator 8 despite the restriction of the output
voltage of the frequency converter 4.
Fig. 4 presents in more detail the operation of an electric drive 2 according to a first
embodiment of the invention when the output voltage of the frequency converter 4 is
limited when using the adjustment device 1 described above. In this case the elevator
drives in the heavy direction such that the force effect of the electric motor of the
hoisting machine is parallel with the direction of movement of the suspension ropes that
are on the traction sheave of the hoisting machine. The output voltage of the frequency
converter is not generally limited when the elevator drives in the light direction, because
in this case the electric power returns owing to motor braking from the electric motor to
the direct-current intermediate circuit of the frequency converter 4, and the voltage in
the direct-current intermediate circuit of the frequency converter 4 tries to increase
irrespective of the voltage of the supplying electricity network 33. In Fig. 4 at the time
t0 the value UDC of the intermediate circuit voltage starts to decrease owing to the
voltage reduction of the supplying electricity network. At the same time the value 12 of
the voltage reference of the motor bridge in relation to the maximum value 10 of the
saw-tooth generator of the modulator comparator starts to increase. This is because the
current regulator 5 endeavors to keep the output voltage 9 of the frequency converter
the same as it was before. At the time the voltage reference 12 of the motor bridge
reaches the aforementioned maximum value 10 of the saw-tooth generator, and the
length |U| (horizontal dashed line) of the phasor of the voltage reference of the motor
bridge is limited to the maximum value of the saw-tooth generator. In this case the
stator current of the electric motor and at the same time the torque produced by the
electric motor start to decrease; when the torque decreases, the speed 19 of the electric
motor also starts to fall. When the speed of the electric motor falls, the source voltage of
the rotor and thereby the supply voltage required by the electric motor also decreases.
At the time t2 when the speed of the electric motor falls, the supply voltage required by
the electric motor decreases to below the maximum output voltage 9 of the frequency
converter, in which case the voltage reference 12 of the motor bridge of the frequency
converter decreases again to slightly below the permitted maximum value 10 of the
voltage reference determined by the saw-tooth generator of the modulator comparator,
and the value of the motor current adjusts to the value according to the current reference
of the current regulator 5. In this embodiment of the invention the control part 28 of the
adjustment device 1 continues the interrupted operation of the speed regulator 8
immediately when the voltage reference decreases to slightly below the aforementioned
permitted maximum value 10 of the voltage reference. The control part 28 sets, as the
initial value of the speed reference, the value of the measured speed 19 of the electric
motor at that moment, in which case the operation of the speed regulator 8 continues.
With this it can be ensured that restarting of the speed regulator 8 does not produce an
extra torque shock in the motor 3. The control part 28 calculates the speed reference 18
from the initial value of the speed reference onwards with a certain jerk such that the
speed of the motor, and thereby of the elevator car, returns softly back to the phase of
even speed. After this the movement of the motor, and thereby of the elevator car,
continues under speed regulation at an even reduced speed. At the time t3 the voltage
reduction of the supplying network starts to disappear, in which case the intermediate
circuit voltage UDC starts to increase and the value of the voltage reference of the motor
bridge of the frequency converter starts to decrease. This is because the same output
voltage 9 of the frequency converter can now be achieved with a smaller value of the
voltage reference 12. At the time t5 the value of the voltage reference 1 of the motor
bridge of the frequency converter has decreased to sufficiently below the permitted
maximum value 10 of the voltage reference determined by the saw-tooth generator of
the modulator comparator, in which case the speed of the electric motor, and thereby of
the elevator car, can be increased back to the normal speed by increasing the value of
the speed reference 18.
Fig. 6 presents in more detail the operation of an electric drive 2 according to a second
embodiment of the invention when the output voltage of the frequency converter 4 is
limited when using the adjustment device 1 described above. In the embodiment of the
invention the adjustment device 1 also comprises a voltage regulator 7, by means of
which the output voltage 9 of the frequency converter is adjusted by adjusting the
voltage reference 12 of the motor bridge of the frequency converter as a response to the
measured intermediate circuit voltage UDC of the frequency converter as well as to the
voltage reference 13 of the voltage regulator. The voltage reference 13 of the voltage
regulator is obtained as the output of the current regulator 5. The measurement of the
intermediate circuit voltage UDC has an inversely proportional effect in the voltage
regulator 7 such that the voltage reference 12 of the motor bridge of the frequency
converter increases when the intermediate circuit voltage UDC decreases and decreases
when the intermediate circuit voltage UDC increases. In other words, the effect of the
voltage reduction of the supplying electricity network on the output voltage 9 of the
frequency converter can be compensated by means of the voltage regulator 7. In this
embodiment of the invention the control part 28 of the adjustment device 1 reads the
value of the voltage reference 12 of the motor bridge of the frequency converter 4 and
interrupts the operation of both the speed regulator 8 and the current regulator 5 at the
time ti, when the voltage reference 12 of the motor bridge reaches and goes on to
exceed the maximum value 10 according to the saw-tooth generator of the modulator
comparator. The operation of the voltage regulator 7 continues despite the interruption
of the operation of the speed regulator 8 and of the current regulator 5. In this case the
control part 28 sets for the voltage reference 13 of the voltage regulator 7 the value that
the voltage reference has at the moment of interruption of the operation of the speed
regulator 8 and of the current regulator 5. The value 13 of the voltage reference is kept
constant after interruption of the operation of the speed regulator 8 and of the current
regulator 5. In this case the run with the elevator continues without the speed regulator 8
and the current regulator 5 despite the restriction of the output voltage 9 of the
frequency converter 4. When the voltage reference 12 of the motor bridge in this case
reaches the aforementioned maximum value 10 of the saw-tooth generator of the
modulator comparator, the length |U| (horizontal dashed line) of the phasor of the
voltage reference of the motor bridge is limited to the maximum value of the saw-tooth
generator. In this case the stator current of the electric motor and at the same time the
torque produced by the electric motor start to decrease; when the torque decreases, the
speed 19 of the electric motor also starts to fall. When the speed of the electric motor
falls, the source voltage of the rotor and thereby the supply voltage required by the
electric motor also decreases, in which case the speed of the motor settles at the value
determined by the output voltage of the motor bridge. At the time t3 the voltage
reduction of the supplying network starts to disappear, in which case the intermediate
circuit voltage UDC starts to increase. At the time the voltage reference 12 of the
motor bridge again returns to below the maximum value 10 of the saw-tooth generator
of the modulator comparator. At the time t5 the difference between the voltage reference
12 of the motor bridge and the permitted maximum value 10 of the voltage reference
returns to be the magnitude of the required limit value 15, after which has occurred the
control part 28 of the adjustment device 1 continues the interrupted operation of the
speed regulator 8 and of the current regulator 5. After this the operation of the speed
regulator 8 and likewise the setting of the initial value of the speed reference 18 and the
calculation of the speed reference 18 continues as described above in connection with
the first embodiment.
Presented above is how the output voltage 9 of the frequency converter 4 in relation to
the permitted maximum value 10 of the output voltage is determined on the basis of the
voltage reference 12 of the motor bridge of the frequency converter; the determination
could, however, also be done e.g. by measuring the intermediate circuit voltage UDC of
the frequency converter and also the output voltage 9 of the frequency converter and by
further deducing when the output voltage 9 of the frequency converter reaches the
maximum value of the output voltage that is determined on the basis of the intermediate
circuit voltage UDCThe
invention is not only limited to be applied to the embodiments described above, but
instead many variations are possible within the scope of the inventive concept defined
by the claims below.
CLAIMS
1. Adjustment device (1) in connection with an electric drive (2) of an elevator,
which electric drive of an elevator comprises an electric motor (3);
and which electric drive of an elevator comprises a power supply apparatus (4) of an
electric motor for adjusting the supply voltage of an electric motor;
and which adjustment device comprises means (5, 6 7) for controlling a power supply
apparatus (4) of an electric motor;
and which adjustment device comprises a speed regulator (8) for adjusting the speed of
the electric motor;
characterized in that the adjustment device (1) is arranged to determine the output
voltage (9) of the power supply apparatus of the electric motor in relation to the
permitted maximum value of the output voltage, and in that the adjustment device (1) is
arranged to interrupt the operation of the speed regulator (8) but to continue the
operation of the power supply apparatus (4) of the electric motor when the output
voltage (9) of the power supply apparatus of the electric motor reaches the permitted
maximum value.
2. Adjustment device according to claim 1, characterized in that the adjustment
device (1) is arranged to continue the interrupted operation of the speed regulator (8)
when the difference (15) between the output voltage (9) of the power supply apparatus
of the electric motor and the permitted maximum value of the output voltage returns to
be at least the magnitude of the required limit value.
3. Adjustment device according to any of the preceding claims, characterized in
that the power supply apparatus (4) of the electric motor comprises a motor bridge (16),
which comprises controllable solid-state switches (30, 31), which are switched in
response to the voltage reference (12, 17) of the motor bridge, and in that the adjustment
device (1) is arranged to determine the output voltage (9) of the power supply apparatus
of the electric motor in relation to the permitted maximum value (10) of the output
voltage on the basis of the voltage reference (12, 17) of the motor bridge of the power
supply apparatus of the electric motor. .
4. Adjustment device according to claim 3, characterized in that the adjustment
device (1) is arranged to interrupt the operation of the speed regulator (8) but to
continue the operation of the power supply apparatus (4) of the electric motor when the
voltage reference (12, 17) of the motor bridge of the power supply apparatus of the
electric motor reaches the permitted maximum value (10).
5. Adjustment device according to claim 4, characterized in that the adjustment
device (1) is arranged to limit the length of the phasor of the voltage reference vector of
the motor bridge of the power supply apparatus of the electric motor to the value for the
length of the phasor set by the permitted maximum value (10) of the voltage reference
of the motor bridge of the power supply apparatus of the electric motor.
6. Adjustment device according to any of claims 3 - 5, characterized in that the
adjustment device (1) is arranged to continue the interrupted operation of the speed
regulator (8) when the difference (15) between the voltage reference (12, 17) of the
motor bridge of the power supply apparatus of the electric motor and the permitted
maximum value (10) of the voltage reference returns to be at least the magnitude of the
required limit value.
7. Adjustment device according to any of claims 4 - 6, characterized in that the
aforementioned permitted maximum value (10) of the voltage reference is determined
on the basis of the maximum value of the modulator comparator of the adjustment
device (1).
8. Adjustment device according to any of claims 2 - 7, characterized in that the
speed regulator (8) is arranged to adjust the speed (19) of the electric motor towards the
value of the speed reference (18), and in that the speed regulator (1) is arranged to set
the initial value of the speed reference (18) to correspond to the speed (19) of the
electric motor when the interrupted operation of the speed regulator continues.
9. Adjustment device according to any of the preceding claims, characterized in
that the adjustment device (1) is arranged to keep the value (13, 20) of at least one
adjustment parameter of the power supply apparatus of the electric motor constant after
s
the operation of the speed regulator (8) has been interrupted.
10. Adjustment device according to claim 9, characterized in that the adjustment
device comprises a current regulator (5) for adjusting the current of the electric motor,
and in that the aforementioned adjustment parameter of the power supply apparatus of
the electric motor to be held constant is the current reference (20) of the current
regulator.
11. Adjustment device according to claim 9 or 10, characterized in that the
adjustment device comprises a voltage regulator (7) for adjusting the output voltage (9)
of the power supply apparatus of the electric motor, and in that the aforementioned
adjustment parameter of the power supply apparatus of the electric motor to be held
constant is the voltage reference (13) of the voltage regulator.
12. Adjustment device according to any of claims 9 - 11, characterized in that the
adjustment device (1) is arranged to set the aforementioned adjustment parameter (13,
20) of the power supply apparatus of the electric motor, which parameter is to be held
constant after the operation of the speed regulator (8) has been interrupted, to
correspond to the value of the adjustment parameter in question when the operation of
the speed regulator (8) is interrupted.
13. Adjustment device according to any of the preceding claims, characterized in
that the adjustment device (1) is arranged to adjust the current (21) of the electric motor
towards the value of the current reference (13) for adjusting the torque of the electric
motor.
14. Electric drive (2) of an elevator, which electric drive comprises a hoisting
machine (22), which hoisting machine comprises an electric motor (3);
and which electric drive of an elevator comprises a power supply apparatus (4) of the
electric motor;
characterized in that the electric drive of the elevator comprises an adjustment device
(1) according to any of claims 1 - 13 for controlling the electric drive (2) of the
elevator, and in that the electric drive (2) of the elevator is arranged to continue the
current supply occurring to the electric motor (3) with the power supply apparatus (4) of
the electric motor when the output voltage (9) of the power supply apparatus of the
electric motor reaches the permitted maximum value.
15. Electric drive of an elevator according to claim 14, characterized in that the
power supply apparatus (4) of an electric motor is a frequency converter.
16. Electric drive of an elevator according to claim 14 or 15, characterized in that
the electric motor (3) is a permanent-magnet synchronous motor.
17. Electric drive of an elevator according to any of claims 14 - 16, characterized
in that the adjustment device (1) is arranged to interrupt the operation of the speed
regulator (8) but to continue the current supply to the stator of the electric motor (3)
when the output voltage (9) of the power supply apparatus of the electric motor reaches
the permitted maximum value.
18. Method for controlling an electric drive of an elevator, characterized in that:
- the output voltage (9) of the power supply apparatus of the electric motor in
relation to the permitted maximum value of the output voltage is determined
- the operation of the speed regulator (8) is interrupted but the operation of the
power supply apparatus (4) of the electric motor is continued when the output
voltage (9) of the power supply apparatus reaches the permitted maximum
value.
19. Method according to claim 18, characterized in that:
- the interrupted operation of the speed regulator (8) is continued when the
difference (15) between the output voltage (9) of the power supply apparatus of
the electric motor and the permitted maximum value of the output voltage
returns to be at least the magnitude of the required limit value.
20. Method according to claim 19, characterized in that:
the initial value of the speed reference (18) is set to correspond to the speed (19)
of the electric motor, when the interrupted operation of the- speed regulator
continues.