Method and apparatus for controlling voltage reflections using a motor controller
AssigneeAllen-Bradley Company, Inc.
InventorsRussel J. Kerkman, David Leggate, Gary L. Skibinski
Life of this patent
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Abstract
A method and apparatus for eliminating greater than twice over voltage by altering firing signals provided to a PWM inverter. The signals are altered by either limiting their maximum and minimum on-times or eliminating signal changes in a symmetrical fashion so that the overall fundamental component and magnitude of a resulting low frequency alternating voltage is substantially unaltered.
Claims22
A method to be used with a motor controller generating firing pulses to control an 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 exciting voltage greater than twice the maximum intended amplitude by modifying the firing pulses to provide modified firing pulses, the method comprising the steps of:
- (a) identifying firing pulse characteristics;
- (b) comparing the firing pulse characteristics to an overvoltage characteristic set known to cause greater than twice overvoltage;
- (c) where the firing pulse characteristics match the overvoltage characteristic set, generating a modified firing pulse having modified characteristics that do not cause greater than twice overvoltage;
- and
- (d) modifying subsequent firing pulses to compensate for the effect of the modified firing pulse.
An apparatus to be used with a motor controller generating firing pulses to control an inverter, the inverter providing exciting voltage to a motor corresponding to the firing pulses, the voltage having a maximum intended amplitude, the apparatus for substantially eliminating exciting voltage greater than twice the maximum intended amplitude by modifying the firing pulses to provide modified firing pulses, the apparatus comprising:
- (a) means for identifying firing pulse characteristics;
- (b) means for comparing the firing pulse characteristics to an overvoltage characteristic set known to cause greater than twice overvoltage;
- (c) where the firing pulse characteristics match the overvoltage characteristic set, means for generating a modified firing pulse having modified characteristics that do not cause greater than twice overvoltage;
- and
- (d) means for modifying subsequent firing pulses to compensate for the effect of the modified firing pulse.
Dependencies are inferred from the claim text.