Eaton Intelligent Power Limited

Eaton Corporation

Stan Rex Simms

Thomas Arthur Farr

Gabriel Teixeira Braga

Irving Albert Gibbs

Hanning Tang

John David Maurin, Jr

Geraldo Nojima

Benjamin Stewart Wells

Donovan Gray

John David Maurin

Methods of testing a multilevel inverter include selectively pulsing (i.e., attempting to turn on) at least one of the inner and outer switches of the inverter and determining a status of at least one of the inner switches, the outer switches and the neutral clamping diodes of the inverter based whether the pulsed at least one of the inner and outer switches desaturates. The pulsing may be preceded by charging the DC bus to a predetermined voltage magnitude that is less than a nominal working voltage magnitude of the DC bus, e.g., the predetermined voltage magnitude may be around 50% or less of the nominal working voltage magnitude.

Inverter diagnostic testing methods and apparatus

Inventive concepts herein relate to mitigating phase current oscillations and vibrations in a spinning, lightly loaded three-phase electric motor. A motor starter can transition between various acceleration profiles defined by unique firing angles and/or firing angle rates of change. These transitions adjust the firing angle of thyristors, which directly manage each phase of a three-phase power supply to the motor. The motor start can identify when a motor has residual motion from prior operation and can modulate the firing angle and/or firing angle rate of change accordingly to reduce a duration of time that issues such as phase current oscillations or vibrations might occur.

Control systems and methods for mitigating motor start-up instabilities in lightly loaded conditions near synchronous speed

An apparatus includes a plurality of DC buses and a plurality of inverter circuits, respective ones of which are coupled to respective ones of the plurality of DC buses. The apparatus further includes a control circuit configured to generate a representative DC voltage signal based on DC voltage signals for respective ones of the DC buses, to generate a first modulation control signal from the representative DC voltage signal, to generate second modulation control signals for the respective inverter circuits from the representative DC voltage signal and the first modulation control signal that are normalized based on the DC voltage signals for the buses and the representative DC voltage signal, and to modulate the inverter circuits responsive to respective ones of the second modulation control signals. The representative DC voltage signal may represent a maximum of the DC voltages for the respective DC buses.

Adjustable frequency drives using normalized modulation control signals to compensate for phase imbalance and methods of operating the same

A reduced voltage starter for electric motors comprises a controller, and a plurality of semiconductor switches to selectively connect a power source to a motor. The controller is configured to apply a first voltage ramp to provide a controllable fraction of the full line voltage to the motor, while maintaining a current flow to be within a programmable current limit during motor startup. The controller is further configured to implement a bumpless force transition, by applying a second voltage ramp when the speed of the motor is below the rated motor speed, and force transition criteria correlated with overheating of the semiconductor switches and/or a connected load are met.

Apparatus and methods for reduced voltage starting of motors with bumpless force transition

Pairs of phases of an AC power source are connected to pairs of phases of a motor in a first sequence that repeats at a first frequency. The motor is braked by connecting pairs of phases of the AC power source to pairs of phases of the motor in a second sequence that is reversed with respect to the first sequence and that repeats at a second frequency less than the first frequency. In further aspects, pairs of phases of an AC power source are connected to pairs of phases of a motor in a first sequence. The motor is subsequently disconnected from the AC power source for a predetermined dwell interval having a duration greater than a time constant of the motor. The motor is braked using a second sequence that is reversed with respect to the first sequence.

Methods of braking motors and motor starters employing the same

A reduced voltage soft starter (RVSS) includes a switching circuit configured to selectively couple an AC power source to a motor and a control circuit configured to sense a line voltage provided to the switching circuit to produce a first voltage signal, to sense a current of the motor to generate a current signal and to generate a second voltage signal representative of a voltage of the motor responsive to the first voltage signal and the current signal. The control circuit may be further configured to generate an estimate of a torque of the motor responsive to the second voltage signal and to control the torque of the motor responsive to the torque estimate.

Motor voltage synthesis in reduced voltage soft starters and motor starters employing the same

A converter of a variable frequency drive (VFD) is operated in a ramp-up mode to produce an AC output voltage for accelerating a motor. A loading of the converter is determined concurrent with the ramp-up mode. Transfer of the motor to a bypassed mode is conditioned on whether the determined loading in the ramp-up mode meets a criterion. In some embodiments, conditioning transfer to the bypassed mode comprises foregoing transition to the bypassed mode based on a comparison of the determined loading to an underloading threshold.

Methods of protecting motors driven by variable frequency drives and variable frequency drive systems employing the same

An apparatus includes a magnetometer-based current sensor (e.g., a Hall-effect or fluxgate-based current sensor) configured to sense a magnetic field generated by a current in at least one conductor connecting a motor drive output to a motor and to responsively produce a first current sense signal and a magnetometer-based voltage sensor (e.g., a Hall-effect or fluxgate-based voltage sensor) configured to sense a magnetic field generated in response to a voltage of the at least one conductor and to responsively produce a first voltage sense signal. The apparatus further includes a signal conversion circuit configured to receive the first current sense signal and the first voltage sense signal and to generate a second current sense input and a second voltage sense input for provision to a current sense input and a voltage sense input, respectively, of a motor protection relay that protects the motor.

Motor protection relay interface using magnetometer-based sensors

An apparatus, such as an adjustable frequency drive (AFD), includes an inverter configured to be selectively coupled to a motor in a first mode and an AC line in a second mode and a control circuit configured to operate the inverter as a motor drive in the first mode and as a power compensator in the second mode. The power compensator may provide power factor correction. The control circuit may include a scalar controller configured to control the inverter according to a voltage vs. frequency characteristic determined by a field weakening point reference and the control circuit may vary the field weakening point reference in the second mode. The inverter may have an input coupled to a DC bus and the control circuit may be configured to adjust a frequency of the inverter in the second mode to increase a voltage on the DC bus.

Adjustable frequency drive systems and methods of employing power compensation

A motor starter includes a plurality of semiconductor switches configured to couple respective phases of an AC power source to respective phases of a motor and a control circuit configured to configured to selectively operate the semiconductor switches to gradually increase a voltage applied to the motor, to determine root mean square (RMS) current values of a current of the motor as the voltage increases, and to cause the semiconductor switches to apply a full voltage or a more steeply ramping voltage to the motor responsive to the RMS current values meeting a criterion.

Reduced voltage soft starter apparatus and methods using current-controlled transitions

An apparatus includes a first DC bus, a second DC bus, a first converter circuit coupled to the first DC bus, and a second converter circuit coupled to the second DC bus. The apparatus further includes a limiter circuit coupled to the second DC bus, a first control circuit configured to sense a voltage on the first DC bus and to responsively control the first converter circuit to limit the voltage on the first DC bus, and a second control circuit configured to sense a voltage on the second DC bus and to responsively control the limiter circuit to limit the voltage on the second DC bus. The apparatus may include a modulation conversion circuit configured to provide a set of switch control signals to the converter circuits and implemented in a module that is also used to implement the second control circuit.

Bus voltage limiter for converter apparatus with multiple DC buses

An apparatus, such as a variable frequency drive (VFD), includes a rectifier, a DC bus coupled to an output of the rectifier and at least one capacitor coupled to the DC bus. The apparatus further includes a normally-conducting switch coupled to the DC bus and configured to discharge the at least one capacitor in a conducting state and a control circuit configured to control the normally-conducting switch responsive to an input to the rectifier. The control circuit may be configured to control the normally-conducting switch responsive to a voltage at the input of the rectifier. The control circuit may include a regulator circuit having an input coupled to the input of the rectifier and a driver circuit coupled to an output of the regulator circuit and configured to drive a control terminal of the normally-conducting switch.

Converter apparatus using source-activated discharge circuits

In one embodiment, a variable frequency drive system includes a main contactor, a variable frequency drive, a charging module structured to generate a magnetizing AC voltage, wherein the charging module is structured to selectively provide the magnetizing AC voltage to a transformer of the variable frequency drive, and a sensing and control circuit having a number of sensors operably associated with the variable frequency drive. The sensing and control circuit is structured to detect a short circuit condition in the variable frequency drive when the magnetizing AC voltage is provided to the transformer based on an output of at least one of the number of sensors, and responsive thereto prevent the main contactor from being closed and thereby prevent the main AC voltage from being provided to the transformer.

System and method for starting a variable frequency drive with reduced arc flash risk

A system, and associated method, for controlling a motor drive coupled to an AC power source in a condition wherein the motor drive is generating a regenerative current. The system includes a plurality of electronic switching devices structured to be provided in anti-parallel connection with a plurality of rectifier diodes of the motor drive, and a controller structured and configured to receive a number of phase voltages from the AC power source, determine a grid angle for the AC power source using the number of phase voltages, and generate a number of control signals for controlling the electronic switching devices using the grid angle when the motor drive is generating the regenerative current.

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Arden, NC, United States of America

Stan Rex Simms