US 11,811,345 B1
Methods of protecting motors driven by variable frequency drives and variable frequency drive systems employing the same
Stan Rex Simms, Arden, NC (US); Thomas A. Farr, Candler, NC (US); and Donovan Gray, Hendersonville, NC (US)
Assigned to Eaton Intelligent Power Limited, Dublin (IE)
Filed by Eaton Intelligent Power Limited, Dublin (IE)
Filed on Jun. 8, 2022, as Appl. No. 17/805,999.
Int. Cl. G01K 7/00 (2006.01); H02P 27/06 (2006.01); H02P 23/20 (2016.01)
CPC H02P 27/06 (2013.01) [H02P 23/20 (2016.02)] 20 Claims
OG exemplary drawing
 
1. 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.
 
11. 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.