Procedure and apparatus for compensating the slip of an induction machine
First Claim
1. A method for adjusting the speed of an induction motor comprising the steps of:
- (a) providing a first speed reference signal for the motor;
(b) producing a second reference signal based on the first speed reference signal;
(c) producing at least one motor supply signal based on the second reference signal;
(d) supplying the at least one motor supply signal to the motor;
(e) converting the second reference signal to a third speed reference signal having a voltage proportional to a synchronous speed of the motor;
(f) producing a speed frequency signal having a frequency proportional to the synchronous speed of the motor, based on the third speed reference signal;
(g) providing a motor frequency signal having a frequency proportional to the actual speed of the motor;
(h) producing a correction signal proportional to a slip of the motor, based on the motor frequency signal of said step (g) and the speed frequency signal of said step (f); and
(i) correcting the second reference signal of said step (b) based on the correction signal of said step (g).
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Abstract
The invention relates to a procedure and an apparatus for adjusting the speed of an induction machine (1) fed by a frequency converter or an inverter (2) to a value corresponding to a reference value (fR). In the procedure, a frequency signal (nm) depending on the actual speed of the motor is generated and the reference value (fR) Of the motor speed is corrected by means of a correction signal (C) proportional to the slip of the motor. The corrected reference value is used as a frequency reference (fS) for the frequency converter or inverter. According to the invention, the correction signal (C) proportional to the slip is generated with the aid of the frequency signal (nm) depending on the actual motor speed and another frequency signal (ns '"'"') formed from the frequency reference (fs) of the inverter. When the motor speed changes, e.g. due to variation in the load, the reference frequency of the inverter is corrected correspondingly.
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Citations
19 Claims
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1. A method for adjusting the speed of an induction motor comprising the steps of:
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(a) providing a first speed reference signal for the motor; (b) producing a second reference signal based on the first speed reference signal; (c) producing at least one motor supply signal based on the second reference signal; (d) supplying the at least one motor supply signal to the motor; (e) converting the second reference signal to a third speed reference signal having a voltage proportional to a synchronous speed of the motor; (f) producing a speed frequency signal having a frequency proportional to the synchronous speed of the motor, based on the third speed reference signal; (g) providing a motor frequency signal having a frequency proportional to the actual speed of the motor; (h) producing a correction signal proportional to a slip of the motor, based on the motor frequency signal of said step (g) and the speed frequency signal of said step (f); and (i) correcting the second reference signal of said step (b) based on the correction signal of said step (g). - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. An apparatus for adjusting the speed of an induction machine comprising:
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a sensor for generating a motor frequency signal proportional to the actual speed of the machine; controller means for producing a speed reference signal having a voltage proportional to a synchronous speed of the machine; an oscillator for generating a speed frequency signal having a frequency proportional to the synchronous speed of the motor, based on the speed reference signal; a phase comparator for determining a phase difference between the motor frequency signal and the speed frequency signal, and for producing a phase difference pulse signal; correcting means for correcting the speed reference signal based on the phase difference pulse signal; filtering means for filtering the phase difference pulse signal to produce a correction signal proportional to a slip of the machine; wherein said controller means corrects the speed reference signal based on the correction signal. - View Dependent Claims (14, 15, 16, 17, 18, 19)
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Specification