Methods of protecting motors driven by variable frequency drives and variable frequency drive systems employing the same
AssigneeEaton Intelligent Power Limited
InventorsStan Rex Simms, Thomas A. Farr, Donovan Gray
Life of this patent
Estimating the term…
Abstract
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.
Claims20
A method of operating a variable frequency drive (VFD), the method comprising:
- operating a converter of the VFD in a ramp-up mode to produce an AC output voltage for ramping up a speed of a motor;
- determining a loading of the converter in the ramp-up mode;
- and
- conditioning transfer of the motor from the ramp-up mode to a bypassed mode in which the converter is bypassed and an AC source is connected to the motor on whether the determined loading in the ramp-up mode meets a criterion.
A system comprising:
- a converter configured to drive a motor;
- a bypass switch configured to bypass the converter and connect an AC source to the motor;
- and
- a control circuit configured to operate the converter in a ramp-up mode to produce an AC output voltage for ramping up a speed of the motor, to determine a loading of the converter in the ramp-up mode and to condition transfer of the motor from the ramp-up mode to a bypassed mode in which the bypass switch bypasses the motor and connects an AC source to the motor based on whether the determined loading in the ramp-up mode meets a criterion.
Dependencies are inferred from the claim text.