Dc motor drive using combined armature and field control

Claim 2

A DC motor drive for a motor having an armature and associated field winding, comprising: an armature feedback loop having means responsive to: a. the current flow in said armature, b. an input command signal, and c. the speed of said armature for providing a control of the current to said armature to thereby provide speed control; and, a field feedback loop having means responsive to: a. the voltage across said armature and b. the line voltage supplied to said armature for providing a control of the field intensity to assure that the back EMF of said armature is always less than the available DC voltage supplied to said armature, whereby a faster response time of the armature throughout its speed range is realized over the response time occurring when only the field is controlled, the torque of said motor is held substantially constant in the range below base speed, and the horsepower is held substantially constant above the base speed of the motor.

Claim 3

A DC motor drive using combined armature and field control comprising, in combination: a motor armature and associated field winding control; a source means of DC bidirectional current connected to said armature and including silicon controlled rectifiers; and armature feedback loop including: a. a current sensor connected in series with said armature for providing an armature current signal constituting a function of the current in said armature; b. a command source providing a command signal; c. means responsive to a function of the speed of said motor armature for providing a reference signal; d. an error detector receiving said command signal and reference signal for providing an output signal constituting a function of said command signal and reference signal; and e. trigger means receiving said armature current signal and output signal and providing a current control gate signal to said silicon-controlled rectifiers in said source such that current is supplied to said armature in accordance with changes in said current control signal to thereby control the speed of said armature; and a field feedback loop including: a. a voltage sensor connected across said armature and a current sensing line from said current sensor connected to the output of said voltage sensor for providing an armature voltage signal constituting a function of the voltage less the IR drop across said armature; b. a line voltage detector providing a line voltage signal proportional to the line voltage in said source; and, c. differential amplifier means receiving said armature voltage signal and line voltage signal for providing a regulating signal to said field winding control to control the intensity of the field in a manner to maintain the back EMF of said armature less than the available DC voltage from said source means, whereby said DC current source means is always capable of driving more current to the armature to increase the armature speed throughout the speed range of the motor.

Claim 4

A DC motor drive using combined armature and field control comprising, in combination: a motor armature and associated field winding control; a source means of DC bidirectional current connected to said armature and including silicon controlled rectifiers; and armature feedback loop including: a. a current sensor connected in series with said armature for providing an armature current signal constituting a function of the current in said armature; b. a command source providing a command signal; c. means responsive to a function of the speed of said motor armature for providing a reference signal; d. an error detector receiving said command signal and reference signal for providing an output signal constituting a function of said command signal and reference signal; and e. trigger means receiving said armature current signal and output signal and providing a current control gate signal to said silicon-controlled rectifiers in said source such that current is supplied to said armature in accordance with changes in said current control signal to thereby control the speed of said armature; and a field feedback loop including: a. a voltage sensor connected across said armature and a current sensing line from said current sensor connected to the output of said voltage sensor for providing an armature voltage signal constituting a function of the voltage less the IR drop across said armature; b. a line voltage detector providing a line voltage signal proportional to the line voltage in said source; and, c. differential amplifier means receiving said armature voltage signal and line voltage signal for providing a regulating signal to said field winding control to control the intensity of the field in a manner to maintain the back EMF of said armature less than the available DC voltage from said source means, whereby said DC current source means is always capable of driving more current to the armature to increase the armature speed throughout the speed range of the motor.

Claim 5

The subject matter of claim 2, in which said source means of DC current includes a three-phase AC power source; and a transformer having its input connected to said source; said silicon-controlled rectifiers being connected betwEen the output of said transformer and said armature, said current control signal being connected to the trigger control electrodes of said silicon-controlled rectifiers to gate their operation, and said line voltage a signal being derived from the output of said transformer.