Method and circuit for reducing the torque ripple of a rotating-field machine

Claim 2

In a drive system for a rotating machine wherein the machine is coupled to a multiphase AC line through a first converter, a DC link and a second converter, said system having means for controlling the current flowing in the DC link, a method of reducing the torque ripple comprising: a. measuring the actual value of torque developed by the machine; b. establishing a predetermined reference value of torque which is to be maintained; c. comparing the measured value of torque with said predetermined reference value to develop an error signal; and d. providing said error signal as a correction term to the means for controlling current in the DC link.

Claim 3

In a drive system for a rotating machine wherein the machine is coupled to a multiphase AC line through a first converter, a DC link and a second converter, said system having means for controlling the current flowing in the DC link apparatus for reducing the torque ripple comprising: a. means to measure the torque developed by the machine and to provide an output signal indicative thereof; b. means to develop a reference torque signal; c. means to difference said output signal and said reference signal to obtain an error signal; and d. means to provide said error signal as a correction term to the means for controlling the current in the DC link.

Claim 4

In a drive system for a rotating machine wherein the machine is coupled to a multiphase AC line through a first converter, a DC link and a second converter, said system having means for controlling the current flowing in the DC link apparatus for reducing the torque ripple comprising: a. means to measure the torque developed by the machine and to provide an output signal indicative thereof; b. means to develop a reference torque signal; c. means to difference said output signal and said reference signal to obtain an error signal; and d. means to provide said error signal as a correction term to the means for controlling the current in the DC link.

Claim 5

The invention according to claim 2 wherein said error signal is provided to a torque control and wherein said means for providing comprise means to add the output of said torque control to a reference value representing the constant current desired in the DC link.

Claim 6

The invention according to claim 3 and further including a first absolute value circuit having said output signal as an input and providing its output to said means to difference.

Claim 7

The invention according to claim 4 and further including a second absolute value circuit having said reference signal as an input and providing its output to said means to difference.

Claim 8

The invention according to claim 2 wherein said means to measure comprises a torque transducer mechanically coupled to the rotor of the machine.

Claim 9

The invention according to claim 2 wherein said means to measure comprises: a. means to sense the current being fed to the machine; b. means to sense the voltage being fed to the machine; and c. a torque computer having the outputs of said current sensing and voltage sensing means as inputs.

Claim 10

The invention according to claim 2 wherein said means to develop a reference torque signal comprises a potentiometer.

Claim 11

The invention according to claim 3 wherein there is a speed control circuit associated with the rotating-field machine and wherein said reference torque signal is obtained from the speed control.