Claims:I/We Claim:
1. A device 100 for controlling switching ON and OFF of a motor, the device
coupled between a grid 110 and a 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 140 via
a capacitor 130, wherein the capacitor 130 is configured to store electrical
energy and supply the electrical energy to the inverter 140 via an inductance
150 to the motor 190, the inductance configured to store energy in the form of
a magnetic field;
- 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 inductance 150 to the motor 190,
wherein the thyristor 160 is configured to be a switch connecting the gird 110
to the motor 190a control circuit 170 configured to switch ON the thyristor and
switch OFF the inverter to supply power to the motor, and control circuit 170
configured to switching OFF the thyristor 160and switch ON the inverter 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.
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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.
4. The device as claimed in claim 1, wherein a Voltage/frequency ratio is
controlled by the capacitor such that the frequency reaches a steady state
within a pre-defined time.
5. The device as claimed in claim 4, wherein the after attaining a steady state the
control circuit is configured to switches ON the thyristor and switched OFF the
inverter.
6. The device as claimed in claim 4, 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.
7. The device as claimed in claim 4, wherein an internal reference is generated for
the frequency, and synchronizing the frequency and phase of the grid.
8. The device as claimed in claim 6, wherein during synchronization the inverter
is in an OFF state, the Thyristor is switched OFF in a blanking time is provided
by control, wherein the blanking time is of the order of a few milliseconds.
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9. The device as claimed in claim 7, wherein the Inverter is turned ON and using
the voltage to the frequency ratio, the voltage across the motor is gradually
decreased, thereby attaining a soft stop without any spikes.
10. A system comprising the device as claimed in any of the preceding claims 1 to
9. , 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.
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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, the device comprising a rectifier coupled to the grid to receive an
input voltage from the grid, wherein the rectifier is coupled to an inverter via a
capacitor, the capacitor configured to store electrical energy and supply the electrical
energy to the inverter, the input voltage from the grid supplied to the motor via
inductance that receives the energy from the inverter, the inductance coupled between
the inverter and the motor, the inductance configured to store energy in the form of a
magnetic field. An input line from the grid prior to the rectifier routed via a thyristor to
an output line from the inductance to the motor, wherein the thyristor is a switch
connecting the gird to the motor and switching ON and switching OFF the thyristor for
supplying energy to the motor controlled by a control circuit coupled to the device.
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
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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 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
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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
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.
An embodiment 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
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embodiment, it reduces any electric current surge on starting, and thus improves
overall life of the motors and any associated mechanical system.
One embodiment discloses a device for controlling switching ON and OFF of a
motor, the device coupled between a grid and a motor, the grid supplying power. 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 is coupled to an
inverter via a capacitor, wherein the capacitor is configured to store electrical energy
and supply the electrical energy to the inverter. In a further embodiment, input voltage
from the grid is supplied to the motor through the inverter. In a further embodiment, an
inductance is coupled between the inverter and the motor, wherein the inductance
configured to store energy in the form of a magnetic field.
In a further embodiment, an input line from the grid prior to the rectifier is
routed via a thyristor to an output line from the inductance to the motor. In a further
embodiment, the thyristor is a switch connecting the gird to the motor. In a further
embodiment, switching ON the thyristor to supply power to the motor and switching
OFF the thyristor to shut down the motor is controlled by a control circuit coupled to
the device.
In a further embodiment, the rectifier may be at least one of a single phase
rectifier or a three phase rectifier. In a further embodiment, the rectifier may include
diodes or other electronic components. In a further embodiment, the rectifier is
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described within the scope of the present disclosure 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.
In a further embodiment the inverter is at least one of a single phase inverter or
a three phase inverter. In a further embodiment, the inverter may include switches or
other electronic components. In a further embodiment, an inverter is an electronic
device or circuitry that changes direct current (DC) to alternating current (AC).
In a further embodiment, a Voltage to frequency (V/f) ratio is controlled by the
inverter between the motor and the inverter, such that the voltage and frequency of
inverter reaches a steady state within a pre-defined time. In a further embodiment, the
pre-defined time may be set automatically or manually by a user. In a further
embodiment, the control circuit is configured to identify that a steady state is reached
and is further configured to switch ON the thyristor and switched OFF the inverter. In
a further embodiment, after the control circuit attains the steady state, power is
supplied to the motor from the grid via the thyristors thereby attaining a dynamic soft
start and the power is supplied to the motor without any spikes.
In a further embodiment, an internal reference is generated for the frequency&
phase, and subsequently the frequency and phase of the grid is synchronized. In a
further embodiment, during synchronization the inverter is in an OFF state, and the
blanking time is provided by control circuit, wherein the blanking time is of the order
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of a few milliseconds. In a further embodiment, after this the Inverter is turned ON and
using the constant voltage to the frequency ratio, the voltage across the motor may be
gradually decreased, thereby attaining a soft stop without any jerks. A further
embodiment may include a system that includes a device with a control circuit
connected between a grid and a motor for dynamically soft switching ON and
switching OFF the motor.
In one embodiment, the disclosure relates to the development of contactor less
soft starter with smooth transition. In a further embodiment, the Soft starters may be
used to reduce the initial current of the motor resulting in reduction of starting jerk of
the motor. In a further embodiment, the soft starter (also referred to as device) may
reduce any electric current surge, and thus prevents the motor from any mechanical
and electrical shock. In a further embodiment, the soft starter may to ramp up the
voltage from low to high for smooth starting, where the conventional soft starter based
on the thyristor incorporated with separate bypass contactor, thereby enabling the grid
run of the motor. In a further embodiment, a conventional thyristor based soft starter’s
works by firing angle control on input AC waveform and therefore it gives chopped
parts of fundamental frequency AC waveform in the output, leading to poor quality
AC on the output. In a further embodiment, a conventional thyristor based soft starter
works well with the induction motor.
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In a further embodiment, the motors may have a magnet on rotating body jerk
which is observed due to magnet braking torques. In a further embodiment, these jerks
may not be acceptable due to mechanical constraints in various applications such as
submersible motor pump sets etc. In a further embodiment, to overcome shortcoming
with existing motors, the present disclosure has been introduced, which results in
better quality output voltage waveform which intern helps jerk free start& stop unlike
conventional system. 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 in accordance with the embodiments of
the present disclosure. Figure 1 illustrates grid 110, wherein the grid supplies power
and the power supplied may be used to drive several electrical equipment’s including a
motor. Device 100 is used for controlling power supplied to motor 190, wherein
device 100 is configured for switching ON and switching OFF the motor. Under
normal circumstances, there are spikes, surges and jerks in the power supply which
may damage the motor. Device 100 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, 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
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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 a capacitor 130,
wherein the capacitor is configured to store electrical energy and supply the electrical
energy to inverter 140. The input voltage from grid 110 supplied to the motor 190
through the inverter 140, wherein an inductance 150 is coupled between the inverter
140and the motor 190. The inductance is configured to store energy in the form of a
magnetic field.
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 the motor 190, wherein switching ON and switching OFF
thyristor 160 controlled by a control circuit 170. Control circuit 170 is coupled to
rectifier 120, capacitor 130, inverter 140 and inductance 150 and is configure to
control the elements and the power supply within the device.
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.
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.
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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
Capacitor, preferably a shunt capacitor, to charge the capacitor. The inverter in the
circuit draws energy from the capacitor in Step 230. In step 240, 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 250, 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 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 270, 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
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power of the grid and a short time delay is allowed. In step 330, the control circuit
switches OFF the Thyristor. In step 340, a few milliseconds time delay is allowed.
Preferably about 10 milliseconds is found to be ideal time. In step 350, the inverter is
turned ON and the thyristor is switched OFF. In step 360, V/f is now controlled such
that it decreases the voltage gradually across the motor. In step 370, the motor is
switched off in a smooth manner, which is referred to as 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 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.
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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.