US 5,451,846 A · Low current compensation control for thyristor armature power supply

Abstract

A control system for energizing a direct current (DC) motor with alternating current (AC) power includes a first voltage sensor for a peak voltage of AC power; a second voltage sensor for a counter electromotive force (EMF) of the motor; a current sensor for an armature current of the motor; a digital processor having a first current controller responding to sensed armature current and a current reference, a cooperating second current controller responding to sensed peak voltage, sensed counter EMF and the current reference signal, and a gating circuit responding to the controllers; and a thyristor converter circuit sequentially gating portions of half cycles of AC power to the motor in response to firing signals from the gating circuit. The controllers may control a gate angle of the firing signals, the control system may include a third voltage sensor for a terminal voltage of the motor, and the armature current may have discontinuous and continuous waveforms. The processor may calculate a start of continuous current value which is a function of a calculated peak voltage of the AC power and a calculated counter EMF of the motor. The calculated counter EMF is sensed when an absolute value of sensed armature current is less than the start of continuous current value but, otherwise, the calculated counter EMF is related to motor terminal voltage. The calculated peak voltage of AC power is an average of an absolute value of a peak positive sensed voltage and an absolute value of a peak negative voltage under calculated discontinuous current conditions but, otherwise, the calculated peak voltage is the average plus a calculated commutation notch line voltage loss. The calculated commutation notch line voltage loss may be a function of the gate angle, the sensed armature current and the calculated peak voltage. The gate angle may be a sum of gate angles from the two controllers.

Claims20

Dependent claims

A control system for controlling energization of a direct current (DC) motor from alternating current (AC) power, said control system comprising:

first voltage sensing means sensing a peak voltage of said AC power;
second voltage sensing means sensing a counter electromotive force (EMF) of said motor;
current sensing means sensing an armature current of said motor, said armature current of said motor having during a first interval a discontinuous waveform and having during a second interval a continuous waveform;
digital processor means comprising first current controller means for controlling at least the continuous waveform of said armature current, said first current controller means generating a first control signal in response to said sensed armature current and a current reference signal;
second current controller means for controlling at least the discontinuous waveform of said armature current, said second current controller means generating a second control signal in response to said sensed peak voltage, said sensed counter EMF and said current reference signal;
and means sequentially generating firing signals in response to said control signals;
and
converter means having a plurality of switches sequentially gating portions of half cycles of said AC power to said DC motor in response to said firing signals to provide DC power to said motor.

5 more elements

A control system for controlling energization of a direct current (DC) motor from alternating current (AC) power, said control system comprising:

voltage sensing means sensing a counter electromotive force (EMF) of said motor;
current sensing means sensing an armature current of said motor, said armature current of said motor having during a first interval a discontinuous waveform and having during a second interval a continuous waveform;
digital processor means comprising first current controller means for controlling at least the continuous waveform of said armature current, said first current controller means generating a first control signal in response to said sensed armature current and a current reference signal;
second current controller means for controlling at least the discontinuous waveform of said armature current, said second current controller means generating a second control signal in response to said sensed counter EMF and said current reference signal;
and means sequentially generating firing signals in response to said control signals;
and
converter means having a plurality of switches sequentially gating portions of half cycles of said AC power to said DC motor in response to said firing signals to provide DC power to said motor.

4 more elements

An apparatus for detecting discontinuous armature current for use in a control system controlling energization of a direct current (DC) motor from alternating current (AC) power, said control system having means sequentially generating firing signals, means controlling a gate angle of said firing signals, and converter means having a plurality of switches sequentially gating portions of half cycles of said AC power to said DC motor in response to said firing signals to provide DC power to said motor, said apparatus comprising:

first voltage sensing means sensing a peak voltage of said AC power;
second voltage sensing means sensing a counter electromotive force (EMF) of said motor;
current sensing means sensing an armature current of said motor, said armature current having during a first interval a discontinuous waveform and having during a second interval a continuous waveform with a continuous current;
and
digital processor means comprising means for calculating a current value which occurs at a start of the continuous current, said current value being a function of said sensed peak voltage of said AC power and said sensed counter EMF of said motor;
and means comparing said sensed armature current with said current value, in order to detect the discontinuous waveform.

3 more elements

Dependencies are inferred from the claim text.

Low current compensation control for thyristor armature power supply

Life of this patent

Low current compensation control for thyristor armature power supply

Life of this patent

Abstract

Claims20