Circuitry and method for controlling the firing of a thyristor

Details Circuitry and method for controlling the firing of a thyristor Circuitry and method for controlling the firing of a thyristor

1990-08-14

1991-03-26

Fuller, Benjamin R.

Electric power conversion systems

Current conversion

With condition responsive means to control the output...

323244, 363 84, 363129, H02M 7797

Patent

active

050034553

ABSTRACT:
Circuitry and methods are provided for AC line synchronization of the firing means for phase-controlled thyristors in a DC motor speed control system. A line synchronization method and system is disclosed which eliminates zero offset in the phase command input function. This zero offset, which is cuased by motor counter EMF, occurs in prior art controllers which use zero crossings of the AC line voltages for line synchronization of thyristor firing. This invention provides line synchronization timing intervals of constant duration that terminate at the coincidence of AC line voltage and motor counter EMF with the coincidence being the latest time at which the particular thyristor being controlled is forward biased in the absence of current flow. Application to N-phase AC to DC converters for DC motor speed control is disclosed. Application to N-phase AC to DC converters for control of the DC bus voltage of variable frequency voltage-source inverters controlling the speed of an AC motor or a brushless DC motor is also disclosed.

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patent: 4571668 (1986-02-01), Azusawa et al.
patent: 4748389 (1988-05-01), Nakakuki

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