Method and circuit for the derivation of an analog slip frequency signal of an induction motor in a tachometerless motor drive
US3989991A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Oct 3, 1974 |
| Grant date | Nov 2, 1976 |
| Priority date | — |
| Expiry date | Oct 3, 1994 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH02P23/08
- WIPO fieldElectrical machinery, apparatus, energy
- WIPO sectorElectrical engineering
Abstract
A tachometerless motor drive of the induction motor type is obtained by synthesizing the motor slip frequency from analog signals sensed at the input of the motor. The slip frequency signal so derived is used as one of the parameters for control, beside voltage and/or frequency or current and frequency at the input of the motor. Analog circuitry is used involving the derivation of a numerator N characteristic of E.sub.1 I.sub.1 Cos .theta., where E.sub.1, I.sub.1 and .theta..sub.1 are given by the vectorial representation of the input current and voltage, and of a denominator D = E.sub.1.sup.2 /.omega..sub.1 where .omega..sub.1 is the frequency of the motor supply.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.