Patent ID: 6541933
Filing Date: 2003-04-01
Classification: H02M,H02P

Abstract:
A method to be used with a motor controller including a signal generator, a PWM controller and an inverter, the generator providing modulating waveforms to the PWM controller which compares the modulating waveforms with a carrier signal to generate firing pulses which control the inverter, the inverter providing exciting voltage to a motor corresponding to the firing pulses, the voltage having a maximum intended amplitude, the method for substantially eliminating greater than twice motor overvoltage by modifying the modulating waveforms to provide modified modulating waveforms, the method comprising the steps of, for each modulating waveform:(a) determining a maximum voltage magnitude of the modulating waveform above which greater than twice motor overvoltage is known to occur; (b) comparing the modulating waveform to the maximum voltage magnitude; (c) when the modulating waveform magnitude equals the maximum voltage magnitude, identifying the modulating waveform angle as a first pass through angle; (d) using the first pass through angle to identify at least one subsequent pass through angle at which the modulating waveform should equal the maximum voltage magnitude; and (d) modifying the modulating waveform as a function of the first and at least one subsequent pass through angles thereby providing a modified waveform having characteristics which do not cause greater than twice overvoltage.