Method and device for controlling an electric motor

Abstract

The invention provides a method and a device for controlling an electric motor using pulse-width modulated control signals. Control pulses having a setpoint duty factor and temporally varying pulse widths and pulse spacing are generated in the process, the temporally varying pulse widths and pulse spacing being selected as a function of a load and/or thermal loading of the electric motor and/or its control device.

1 - 15 . (canceled) 
   
   
       16 . A method for controlling an electric motor using pulse-width modulation, the method comprising:
 generating control pulses having a setpoint duty factor and temporally varying pulse widths and pulse spacing;   varying the pulse widths and the pulse spacing so that a sound emission spectrum generated by the control of the electric motor using the control pulses is approximated to a spectrum of ambient noise; and   controlling the electric motor using the control pulses.   
   
   
       17 . The method of  claim 16 , wherein the temporally varying pulse widths and pulse spacing are generated as a function of at least one of a load and a thermal loading of at least one of the electric motor and its control device. 
   
   
       18 . The method of  claim 17 , wherein a minimum period duration and a maximum period duration are specified as a function of at least one of the load and the thermal loading of at least one of the electric motor and its control device. 
   
   
       19 . The method of  claim 18 , wherein the minimum period duration is specified so that it increases with at least one of a rising load and a thermal loading of at least one of the electric motor and its control device. 
   
   
       20 . The method of  claim 18 , wherein the maximum period duration is specified so that it increases with at least one of a rising load and a thermal loading of at least one of the electric motor and its control device. 
   
   
       21 . The method of  claim 16 , further comprising:
 implementing a sound-frequency analysis of ambient noise to obtain a sound-emission spectrum of the environment;   wherein the variation of the pulse widths and the pulse spacing occurs as a function of the sound emission spectrum of the environment.   
   
   
       22 . The method of  claim 16 , wherein the duty factor remains constant regardless of the modulation of the pulse widths. 
   
   
       23 . A device for controlling an electric motor using pulse-width modulation, comprising:
 a generating device to generate control pulses having a setpoint duty factor and temporally varying pulse widths and pulse spacing, wherein the temporally varying pulse widths and pulse spacing are varied so that a noise emission spectrum generated by the control of the electric motor using the control pulses is approximated to a spectrum of ambient noise; and   a control device to control the electric motor using the control pulses.   
   
   
       24 . The device of  claim 23 , wherein the temporally varying pulse widths and pulse spacing are generatable as a function of at least one of a load and a thermal loading of at least one of the electric motor and its control device. 
   
   
       25 . The device of  claim 24 , wherein a minimum period duration and a maximum period duration are specifiable by the generating device as a function of the at least one of the load and the thermal loading of at least one of the electric motor and its control device. 
   
   
       26 . The device of  claim 25 , wherein the minimum period duration is specified so that it increases with at least one of a rising load and a thermal loading of the at least one of the electric motor and its control device. 
   
   
       27 . The device of  claim 25 , wherein the maximum period duration is specified so that it increases with at least one of a rising load and a thermal loading of the at least one of the electric motor and its control device. 
   
   
       28 . The device of  claim 23 , further comprising:
 a sound-frequency analysis device to implement a sound-frequency analysis of ambient noise to obtain a sound emission spectrum of the environment, the pulse widths and the pulse spacing being variable as a function of the noise-emission spectrum of the environment.   
   
   
       29 . The device of  claim 23 , further comprising:
 a detection device to detect the thermal loading of the electric motor.   
   
   
       30 . The device of  claim 29 , wherein the detection device is a thermometer.