US 5,859,513 A · Starting and synchronizing system for line-start permanent magnet motor

Abstract

A system for preventing objectionable large torque pulsations during the starting and synchronization of a line-start permanent magnet motor compares motor speed with motor synchronous speed and power source phase with the motor back-emf phasor. The motor starting armature is coupled to the power source and the PM armature is disconnected from the power source before motor speed has reached to within a predetermined margin of synchronous speed and before the back-emf phasor has dropped below a predetermined phase difference. After motor speed has approached synchronous speed to within the margin and the phase difference has dropped below the predetermined phase difference, connections are reversed so that the starting armature is disconnected from the power source and the PM armature is coupled to the power source.

Claims11

Dependent claims

A starting and synchronizing system for a line-start permanent magnet motor including a starting armature and a PM armature, comprising:

motor speed detection and comparison means for detecting speed of said motor and comparing said speed with synchronous speed of said motor;
phase detection and comparison means for detecting phase of a power source and a back-emf phasor of said motor, comparing said phases, and determining a difference between said phases;
and
switching means for coupling said power source to a starting armature of said motor prior to achieving a predetermined motor speed close to said synchronous speed and prior to the phase difference between said power source and said back-emf phasor dropping below a predetermined phase difference, and disconnecting said power source from said starting armature and coupling said power source to said PM armature after said predetermined motor speed close to said synchronous speed has been achieved and after said phase difference between said power source and said back-emf phasor has dropped below said predetermined phase difference.

1 more element

A method for starting and synchronizing a line-start permanent magnet motor, comprising the steps of:

detecting speed of said motor;
comparing the detected motor speed with synchronous speed of said motor;
detecting the phase of a power source supplying energy to said motor;
determining a back-emf phasor of said motor;
comparing said back-emf phasor against said phase of the power source to obtain any difference therebetween;
coupling said power source to a starting armature of said motor before a predetermined motor speed close to said synchronous speed of said motor is achieved and before said difference in phase between said power source and said back-emf phasor drops below a predetermined value;
and
disconnecting said power source from said starting armature and coupling said power source to a PM armature of said motor after said predetermined motor speed close to said synchronous speed has been achieved and after said difference in phase between said power source and said back-emf phasor has dropped below said predetermined value.

5 more elements

Dependencies are inferred from the claim text.

Starting and synchronizing system for line-start permanent magnet motor

Life of this patent

Starting and synchronizing system for line-start permanent magnet motor

Life of this patent

Abstract

Claims11