Claims:I/We Claim:
1. A device 100 for controlling switching ON and OFF of a motor 190, the device
coupled between a grid 110 and the motor 190, the device 100 comprising:
- a rectifier 120 coupled to the grid 110 to receive an input voltage from
the grid 110 , wherein the rectifier 120 is further coupled to an inverter 150 via a
first element 105 and supply power to the motor 190 via the first element 105
and the inverter 140;
- an input line 162 from the grid 110 prior to the rectifier 120 routed via
a thyristor 160 to an output line 164 from the inverter 140 to the motor 190,
wherein the thyristor 160 is configured to be a switch connecting the gird 110
to the motor 190;
- a control circuit 170 configured to control switching ON the thyristor and
switching OFF the inverter to supply power to the motor and/or configured to
control switching OFF the thyristor 160 and switch ON the inverter 150 to
power OFF the motor.
2. The device as claimed in claim 1, wherein the rectifier is at least one of a single
phase rectifier or a three phase rectifier, wherein the rectifier comprises diodes.
3. The device as claimed in claim 1, wherein the inverter is at least one of a single
phase inverter or a three phase inverter, and the inverter comprises switches.
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4. The device as claimed in claim 1, wherein the first element 105 comprises a first
capacitor 130 coupled to a second capacitor 145 via Inductance 135 and a
booster circuit 140, wherein Capacitor 145 is configured to provide energy to
the motor via the inverter.
5. The device as claimed in claim 4, wherein the booster circuit can operate in
power factor correction mode.
6. The device as claimed in claims 1, wherein the control circuit is configured to
detect health of the grid and on negative determination of health of the grid
prevent switching ON of the motor thereby preventing damage to the motor.
7. The device as claimed in claim 6, wherein the control circuit is configured to
detect a fault with the motor by sensing a current passing through the motor
and/or a voltage across the motor during switching ON and on detection of the
fault further configured to report the fault detected to a user.
8. The device as claimed in claim 4, wherein Capacitor 145 is always at a higher
voltage and/or higher potential than capacitor 130, thereby stopping reverse
flow of current.
9. The device as claimed in claim 4, wherein capacitor 145 is at a higher voltage
due to the boosting performed by the booster circuit and the inductance, thereby
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ensuring operation of the motor is uninterrupted even when the input power
from the grid is low.
10. The device as claimed in claim 1, wherein a Voltage/frequency ratio is
controlled by the Inverter such that the frequency reaches a steady state within a
pre-defined time.
11. The device as claimed in claim 7, wherein the after attaining a steady state the
control circuit is configured to swtiches ON the thyristor and switched OFF the
inverter.
12. The device as claimed in claim 7, wherein after attaining steady state power is
supplied to the motor from the grid via the thyristors thereby attaining a soft
start without any spikes or jerks.
13. The device as claimed in claim 7, wherein an internal reference is generated for
the synchronizing the frequency and phase of the grid.
14. The device as claimed in claim 13, wherein during synchronization the inverter
is in an OFF state, the Thyristor is switched OFF in a blanking time provided by
the control circuit, wherein the blanking time is of the order of a few
milliseconds.
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15. The device as claimed in claim 14, wherein the Inverter is turned ON and using
the fixed voltage to the frequency ratio, the voltage across the motor is
gradually decreased, thereby attaining a soft stop without any spikes.
16. A system comprising the device as claimed in any of the preceding claims 1 to
15. , Description:FIELD OF TECHNOLOGY
This disclosure relates to a motor, and more specifically for digitally controlling
a start operation and stop operation of a motor in a smooth manner.
BACKGROUND
US Patent No. 8896334 B2 describes a system for measuring soft starter current
includes a current monitoring system including a controller and a current transfer
device that includes a first thyristor and a first conductor coupled to the first thyristor
and configured to convey a first current flowing through the first thyristor, wherein the
first current includes current flowing through the first thyristor when the first thyristor
is in an off state. The system also includes a first current sensor configured to sense the
first current and a first current measurement circuit coupled to the first current sensor
and coupleable to the controller and configured to output a first output value to the
controller representative of the first current flowing through the first thyristor. The
controller is configured to determine an impending inoperability of the first thyristor
based on the first current and alert a user if the first current indicates the impending
inoperability.
SUMMARY
Embodiments of the present disclosure are related to a device for controlling
switching ON and OFF of a motor, the device coupled between a grid that supplies
power and a motor. In one embodiment, the device for controlling switching ON and
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OFF of a motor wherein the device is coupled between a grid and a motor comprising a
rectifier coupled to the grid to receive an input voltage from the grid, wherein the
rectifier is further coupled to an inverter via a first elementand supply power to the
motor via the first element. In a further embodiment, an input line from the grid prior to
the rectifier routed via a thyristor to an output line from the inverter to the motor,
wherein the thyristor is configured to be a switch connecting the gird to the motor a
control circuit configured to switch ON the thyristor and switch OFF the inverter to
supply power to the motor. In a further embodiment, a control circuit is configured to
switch OFF the thyristor and switch ON inverter to power OFF the motor. One
embodiment includes a capacitor and an inductance coupled to a booster circuit which
is then coupled to the inverter via a second capacitor, always maintaining the second
capacitor at a higher voltage and preventing reverse flow of power. Other embodiments
are also disclosed.
BRIEF DESCRIPTION OF THE DRAWINGS
For a better understanding of the nature and desired objects of the present
invention, reference is made to the following detailed description taken in conjunction
with the accompanying drawing figures wherein like reference character denote
corresponding parts throughout the several views. Objects, features, and advantages of
embodiments disclosed herein may be better understood by referring to the following
description in conjunction with the accompanying drawings. The drawings are not
meant to limit the scope of the claims included herewith. For clarity, not every element
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may be labeled in every Figure. The drawings are not necessarily to scale, emphasis
instead being placed upon illustrating embodiments, principles, and concepts. Thus,
features and advantages of the present disclosure will become more apparent from the
following detailed description of exemplary embodiments thereof taken in conjunction
with the accompanying drawings in which:
FIGURE 1 illustrates an exemplary block diagram of the device in accordance
with the present disclosure;
FIGURE 2 illustrates an exemplary method for switching ON a motor in
accordance with the embodiments of the present disclosure; and
FIGURE 3 illustrates an exemplary method for switching OFF a motor in
accordance with the embodiments of the present disclosure.
DETAILED DESCRIPTION
Hereinafter, various embodiments of the present disclosure will be described
with reference to the accompanying drawings. It should be noted that all of these
drawings and description are only presented as exemplary embodiments. It is to note
that based on the subsequent description, alternative embodiments may be conceived
that may have a structure and method as disclosed herein, and such alternative
embodiments may be used without departing from the principle of the disclosure as
claimed herein.
It may be appreciated that these exemplary embodiments are provided herein
only for enabling those skilled in the art to better understand and then further
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implement the present disclosure, and is not intended to limit the scope of the present
disclosure in any manner. Besides, in the drawings, for a purpose of illustration,
optional steps, modules, and units are illustrated in dotted-line blocks.
The terms “comprise(s),” “include(s)”, their derivatives and like expressions
used herein should be understood to be open, i.e., “comprising/ including, but not
limited to.” The term “based on” means “at least in part based on.” The term “one
embodiment” means “at least one embodiment”; and the term “another embodiment”
indicates “at least one further embodiment.” Relevant definitions of other terms will be
provided in the description below.
Embodiments of the present invention generally relates to soft starter and more
particularly it relates to a contactor less soft starter for induction and magnet motors. In
a further embodiment, Soft starters may be used to reduce the initial current of the
motor thereby reducing the starting jerk associated with the motor, in a further
embodiment, it reduces any electric current surge on starting, and thus improves overall
life of the motors and any associated mechanical system.
In one embodiment a device for controlling switching ON and OFF of a motor is
disclosed. In a further embodiment, the device is coupled between a grid providing
input power and/or voltage and a motor that draws power from the grid to operate. In a
further embodiment, the device may include a rectifier coupled to the grid to receive an
input voltage from the grid. In a further embodiment, the rectifier may be further
coupled to an inverter via a first element (illustrated as dashed and dotted line) and
supply power to the motor via the inverter.
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In a further embodiment, an input line from the grid prior to the rectifier routed is
provided via a thyristor to an output line from the inverter to the motor. In a further
embodiment, the thyristor may be configured to be a switch connecting the gird to the
motor and is controlled by means of a control circuit, wherein the control circuit is
configured to switch ON the thyristor and switch OFF the inverter to supply power to
the motor by soft start and/or configured to switching OFF the thyristor and switch ON
the inverter to power OFF the motor, thereby reducing any jerks in the power supply to
the motor and ensuring that the motor runs smoothly.
In a further embodiment, the rectifier may at least be one of a single phase rectifier or a
three phase rectifier, wherein the rectifier may include a plurality of diodes. In a further
embodiment, the inverter may at least be one of a single phase inverter or a three phase
inverter, and the inverter may include a plurality of switches.
In a further embodiment, the first element in the device may include a first capacitor
(also referred to as Capacitor C1) coupled to an Inductance (L), the inductance coupled
to a Booster Circuit (B), which is then coupled to a second capacitor (also referred to as
Capacitor C2) before being coupled to the Inverter. In a further embodiment the second
Capacitor provides energy to the motor via the inverter and is always maintained at a
higher potential than the first capacitor because of the booster circuit. In a further
embodiment, the booster circuit may operate in power factor correction mode. In a
further embodiment, the control circuit may be configured to detect health of the grid
and on negative determination of health of the grid, the control circuit may be
configured to prevent switching ON the motor thereby preventing damage to the motor.
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In a further embodiment, the control circuit may be configured to detect a fault with the
motor by sensing current passing through the motor and/or sensing a voltage across the
motor while switching ON. In a further embodiment, the control circuit may be
configured to report the fault detected to a user.
In a further embodiment, capacitor C2 may be always at a higher voltage than capacitor
C1, thereby stopping reverse flow of current in the circuit and prevent malfunctioning
of the circuit. In a further embodiment, capacitor C2 is always maintained at a higher
voltage due to the booster circuit and inductance, hence operation of the motor is
uninterrupted even when the input power from the grid is low, because capacitor C2 is
at a higher potential and is able to sustain power supply to the motor.
In a further embodiment, a Voltage/frequency ratio may be controlled by the Inverter
such that the frequency reaches a steady state within a pre-defined time. In yet a further
embodiment, after attaining a steady state the control circuit is configured to switch ON
the thyristor and switched OFF the inverter, a supply stable power to the motor from
the grid via the thyristors. In a further embodiment, after attaining steady state, i.e., the
V/f ratio reaches a steady state, power may be supplied to the motor from the grid via
the thyristors thereby attaining a soft start without any spikes or jerks.
In a further embodiment, an internal reference is generated for the
synchronizing the frequency and phase of the grid. In a further embodiment, during
synchronization the inverter may be in an OFF state, the Thyristor may be switched
OFF in a blanking time provided by control circuit, wherein the blanking time is of the
order of a few milli seconds. In a further embodiment, the Inverter is turned ON and
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using the fixed voltage to the frequency ratio, the voltage across the motor is gradually
decreased, thereby attaining a soft stop without any spikes or jerks. In a further
embodiment, the present disclosure works with single-phase and three phase
configuration with induction and magnet based motors.
Reference is now made to Figure 1, which illustrates an exemplary embodiment
of a block diagram of a device 100 in accordance with the embodiments of the present
disclosure. Figure 1 illustrates grid 110, wherein the grid supplies power, and power
supplied from the grid may be used to drive several electrical equipment’s, which may
also including motor 190. Device 100 is used for controlling power supplied to motor
190, wherein device 100 is configured for switching ON and switching OFF the motor
in a smooth manner without any jerks or spikes. Under normal circumstances, there are
spikes, surges and jerks in the power supply which may damage the motor. Device 100
(illustrated as dashed line in the Figure) is coupled to grid 110 on one end and to motor
190 on the other end.
The device 100 has rectifier 120 coupled to grid 110 side, and the rectifier
received input power from the grid. Rectifier 120 is an electrical device which converts
an alternating current into a direct current by allowing a current to flow through it in
one direction only. The process is known as rectification, because it "straightens" the
direction of current. Physically, rectifiers take a number of forms, including vacuum
tube diodes, mercury-arc valves, stacks of copper and selenium oxide plates,
semiconductor diodes, silicon-controlled rectifiers and other silicon-based
semiconductor switches. Rectifier 120 is coupled to inverter 140 via first element 105
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(illustrated as dashed and dotted line in the Figure), wherein the first element is
configured to store electrical energy, boost the electrical energy and supply the
electrical energy to inverter 140. The input voltage from grid 110 is supplied to the
motor 190 through the inverter 140 and the first element making device 100 completely
light weight and highly efficient as device 100 can even operate when grid voltage is
low.
First element 105 comprises Capacitor C1 130 coupled to the rectifier of device
100. Capacitor C1 draws energy from rectifier 120 and supplies it to capacitor C2 145
via inductance 135 and booster circuit 140. The inductance 135 in first element 105 is
configured to store energy in the form of a magnetic field. Booster circuit 140 is
configured to boost the input energy from Capacitor C1 and then store the booster
energy in Capacitor C2. Therefore Capacitor C2 will always be maintainer at a higher
potential than Capacitor C1 because of boosting the energy before being supplied to
Capacitor C2. Capacitor C1 gets charged first, and then gives the energy to Capacitor
C2 by using the boosting circuit. Capacitor C2 provides energy to the motor via the
Inverter. Because Capacitor C2 is always at a higher voltage than Capacitor C1, reverse
flow of current/power in the system is prevented thereby safeguarding the motor.
Input line 162 from grid 110 prior to rectifier 120 routed via a thyristor 160 to
an output line 164 from inductance 150 to the motor 190. Tyristor160 is a switch
connecting gird 110 to motor 190, wherein switching ON and switching OFF thyristor
160 controlled by a control circuit 170. Control circuit 170 is coupled to rectifier 120,
first element 105, and inverter 140, and is configure to control the elements and the
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power supply within the device. Control Circuit 170 is also configured to control each
of the elements within the first element 105.
In one embodiment, a breaker circuit can be provided between the capacitor and
the inverter, which is not shown in the block diagram in order to simplify the circuit. In
one embodiment, during shutting OFF and switching ON the motor, any phase or
voltage difference between the grid and the capacitor will lead the current to flow
through the inverter back to C and cause the inverter to fail. Patent application Method
and Apparatus for soft starting and switching of a motor coupled to the grid will
address this issue.
Reference is now made to Figure 2, which illustrates an exemplary method of
switching ON the motor in accordance with the embodiments of the present disclosure.
As illustrated in Step 210 the rectifier draws power from the grid. Power and voltage
are used interchangeably in this disclosure. The rectifier can be a single phase rectifier
or a three phase rectifier. In Step 220, the voltage from the rectifier is supplied to the
first Capacitor, preferably a shunt capacitor, to charge the capacitor. In step 230, the
first capacitor supplies energy to second capacitor from a inductor and boost converter.
The inverter in the circuit draws energy from the second capacitor in Step 240. In step
250, voltage in the motor is increased using V/f control, which is a standard method,
but it should be obvious to one skilled in the art that other method may be used as well,
wherein the V/f ratio cannot be controlled in normal starters/device. In step 260, the
voltage & frequency reaches a steady state, which means that the voltage, frequency &
phase is now the same as the grid and also a specified wait time is completed, which
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may be defined by the user or set automatically. Once a steady state is reached, the
control circuit switches on the thyristors and switches OFF the inverter. In step 280,
power is directly fed from the grid to the motor via the thyristors, which is a steady
state power, thereby avoiding any spikes, power surges and jerks. This is referred to a
soft start of the motor.
Reference is now made to Figure 3, which is an exemplary embodiment of
switching OFF a motor in accordance with embodiments of the present disclosure. The
motor is in ON state and needs to be switched OFF, but should be done in a smooth
manner. In step 310, the thyristors is in an ON state and the inverter is in OFF state. In
step 320, the frequency, voltage & phase of the inverter is synchronized with the power
of the grid and a short time delay is allowed. The boost converter turns on in step 330.
In step 340, the control circuit switches OFF the Thyristor In step 350, a few
milliseconds time delay is allowed. Preferably about 10 millis seconds is found to be
ideal time. In step 360, the inverter is turned ON and the thyristor is switched OFF. In
step 370, V/f is now controlled such that it decreases the voltage gradually across the
motor. In step 380, the motor is switched off in a smooth manner, which is referred to
as soft soft.
The accompanying figures and description depicted and described embodiments
of the present disclosure, and features and components thereof. Those skilled in the art
will appreciate that any particular program nomenclature used in this description was
merely for convenience, and thus the present disclosure should not be limited to use
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solely in any specific application identified and/or implied by such nomenclature.
Thus, for example, the routines executed to implement the embodiments of the
invention, whether implemented as part of an operating system or a specific
application, component, program, module, object, or sequence of instructions could
have been referred to as a "program", "application", "server", or other meaningful
nomenclature. Indeed, other alternative hardware and/or software environments may
be used without departing from the scope of the invention. Therefore, it is desired that
the embodiments described herein be considered in all respects as illustrative, not
restrictive, and that reference be made to the appended claims for determining the scope
of the invention.
Although embodiments of the invention have been described using specific
terms, such description is for illustrative purposes only, and it is to be understood that
changes and variations may be made without departing from the spirit or scope of the
following claims.