A drive circuit for an electric pump motor is provided. The drive circuit includes an inverter and a contactor. The inverter is configured to supply variable frequency current to the electric motor. The contactor is configured to supply the line frequency current to the electric motor.

Drive circuit for electric motors

In the field of variable-speed motor control, a bypass circuit and corresponding bypass electronics (138) can be integrated advantageously with a variable-frequency drive ("VFD") circuit and corresponding electronics (110). Such an integrated bypass can be disposed within a single unitary enclosure housing the VFD. Some advantages of the integrated bypass include reduced size, cost, and/or complexity in the combined VFD/bypass assembly, the ability to manage airflow in bypass without running a fan motor full time, and support for integrated power metering using multi-purposed current transformers (112).

Integrated bypass apparatus, system, and/or method for variable-frequency drives

A system for soft starting a large AC motor may include a variable frequency drive (VFD) having a much lower voltage rating than the rated voltage of the AC motor. The VFD's voltage rating may be in a range of about 33% to about 67% of the AC motor's rated voltage. The AC motor may be coupled to a utility power source via conventional connections to leads of the AC motor's windings. The VFD may be connected to the AC motor via tapped connections within the windings of the AC motor such that the tap voltages are much less than the AC motor's rated voltage. A less expensive VFD may therefore be used to soft start the AC motor instead of a VFD having the same rated voltage as the AC motor. Methods of starting large AC motors with a VFD are also provided, as are other aspects.

Systems, apparatus, and methods for soft starting large AC motors with a variable frequency drive

Hybrid motor drive circuits configured to drive a motor are provided herein. A hybrid motor drive circuit includes an inverter coupled to the motor and configured to drive the motor when a motor commanded frequency is not within a predetermined range of line input power frequencies. The hybrid motor drive circuit also includes a first switch device configured to couple line input power to an output of the inverter when the motor commanded frequency is within the predetermined range of line input power frequencies.

Hybrid drive circuit for variable speed induction motor

Controllers for controlling hybrid motor drive circuits configured to drive a motor are provided herein. A controller is configured to drive the motor using an inverter when a motor commanded frequency is not within a predetermined range of line input power frequencies, and couple line input power to an output of the inverter using a first switch device when the motor commanded frequency is within the predetermined range of line input power frequencies.

Hybrid drive circuit for variable speed induction motor system and methods of control

A Variable Frequency Drive (VFD) supplies power to rotate a motor, controlling both the speed and direction. The method normally used for this power conversion by the VFD results in energy losses and line harmonics. When the motor is driven by the VFD to be rotating at the same speed and direction as if the motor was straight across the incoming AC power, a transfer in power supply to the motor can be made using contactors to bypass the VFD. When in this bypass mode, the energy losses of the VFD are greatly reduced, and the line harmonics due to the VFD are greatly reduced. When it is subsequently recognized that the speed reference has deviated from being the same speed and direction as if the motor was straight across the incoming AC power, a transfer in power supply can be made from using contactors to once again drive the motor from the VFD.

Matthew James Schimke

Papers

Variable frequency drive bypass energy savings