Transistor inverter motor drive having voltage boost at low speeds
US3971972A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Mar 14, 1975 |
| Grant date | Jul 27, 1976 |
| Priority date | — |
| Expiry date | Mar 14, 1995 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH02P27/047
- WIPO fieldElectrical machinery, apparatus, energy
- WIPO sectorElectrical engineering
Abstract
A transistor inverter drive provides variable frequency and variable voltage power to an electric motor and pulse width modulates a predetermined number of harmonic-reduced constant volt/hertz pulses per cycle of motor frequency to selectively vary the motor stator voltage so that constant torque over a wide speed range can be accomplished and increases the number of constant volt/hertz PWM pulses per motor frequency cycle at low motor speeds to boost the stator voltage and thereby compensate for decrease in magnetizing current and in torque which would otherwise occur at low frequencies. Particularly, the drive has first and second oscillators for respectively deriving trains of first and second clock pulses whose frequencies vary at different rates as a function of an analog speed signal; a frequency switch which selects the higher frequency train of clock pulses; a volt/hertz integrator which derives ramp pulses whose leading edges are established by the pulses from the frequency switch and which vary in magnitude as a function of the time integral of the inverter bridge output voltage; a first comparator for deriving a first control pulse when each ramp signal becomes equal to …
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.