Danfoss Power Electronics A/s

Leandro Della Flora

Andreas Doktar

William Giewont

Dan Isaksson

David Michaud

Anton Smith

A circuit comprising a first power node for connection to a positive voltage of a DC link, a second power node for connection to a negative voltage of the DC link and a mid-point power node for connection to a mid-point voltage of the DC-link, the circuit further comprising a three-level neutral point clamped converter module and a brake resistor connection.

Inverter circuit

Three-level inverter and a three-level brake chopper

A method and apparatus is described in which a series of short-circuiting pulses is applied to a motor. A current in the motor is determined after one or more of the series of short circuit pulses has completed. The duration of the short-circuit pulses is adjusted depending on the determined current. The method and apparatus may be used within an arrangement for catching a spinning motor.

Motor control system and method

A method and apparatus for catching a rotating motor is described. Switches (typically the lower switches) of an inverter of a motor drive circuit are short-circuited for a brief period of time. The pulses generated by this process are analyzed to determine the speed and direction of rotation of the motor. The pulses are checked to determine whether they are orthogonal. If they are, the motor velocity determination is deemed to be reliable and then motor is magnetized and normal motor control can be resumed. If not, the motor velocity determination is deemed to be unreliable and a magnetization pulse before the velocity determination step is repeated.

A method of initiating a grid-tied inverter is described, in which in-rush currents and DC overvoltage conditions are reduced or avoided. The method uses a pulse width modulator to drive the inverter under the control of a voltage feedforward signal such that the inverter output is dependent on the measured grid voltage. Then, an AC current feedback controller is enabled and the pulse width modulator is used to drive the inverter under the control of both the voltage feedforward control signal and the feedback control signal.

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Cary, NC, United States of America

Leandro Della Flora