Reversible speed dc motor controller utilizing resonant field reversal

Claim 2

In a speed control circuit for DC electric motors having field windings and a wound rotating armature wherein armature speed is controlled by varying armature voltage and means are provided for transposing terminal polarity of the motor field, the improvement in means for bidirectional operation of the armature, comprising a capacitor in parallel with the motor field, said capacitor facilitating field circuit interruption, and means responsive to loss of field current comprising a switch electrically connected in said speed control circuit such that loss of field current causes said switch to open, which opening initiates control of armature voltage by said speed control circuit.

Claim 3

The improvement of claim 1 where the switch is a transistor.

Claim 4

The improvement of claim 1, where the armature voltage control includes an armature current limiting circuit, further characterized by the use of a resistor, responsive to the existence of field current, to produce the signal that maintains a transistor switch in saturation, the loss of which signal places the transistor in its nonconducting state, thereby activating said current limiting circuit, said activation closing a second transistor switch removing the input signal to the armature voltage control.

Claim 5

In a speed control circuit for DC electric motors, including a means to control armature voltage electrically connected to the output of an amplifier, a speed command potentiometer electrically connected to said amplifier, a negative feedback loop, indicating motor speed, electrically connected to said amplifier, a capacitor electrically connected to said amplifier, and a current limiting circuit electrically connected to said amplifier, comprising an armature circuit resistor, a diode and a current limiting circuit transistor, said diode being electrically connected to the base of said current limiting circuit transistor, the emitter of which transistor is electrically connected to a common conductor, and the collector of said limiting circuit transistor being electrically connected through a third resistor to the base of a transistor switch, said switch being electrically connected in parallel to the capacitor through the emitter and collector of said switch, the capacitor providing an input signal to said amplifier, the improvement comprising means to facilitate directional reversal, said reversal facilitating means comprising a field sensory resistor electrically connected to the motor field, a second resistor, and a field loss transistor having the base electrically connected to said field sensory resistor through said second resistor, the emitter of the field loss transisTor being electrically connected to a common conductor and the collector of said transistor being electrically connected to the base of the current limiting circuit transistor, wherein loss of field current in the field sensory resistor causes loss of bias for the field loss transistor, causing it to cease conduction, thereby allowing the current limiting circuit transistor to reach its conduction state, which conduction provides bias to the transistor switch, closing said switch and discharging the capacitor, thereby removing input signal from the amplifier.

Claim 6

In a speed control circuit for DC electric motors, including a means to control armature voltage electrically connected to the output of an amplifier, a speed command potentiometer electrically connected to said amplifier, a negative feedback loop, indicating motor speed, electrically connected to said amplifier, a capacitor electrically connected to said amplifier, and a current limiting circuit electrically connected to said amplifier, comprising an armature circuit resistor, a diode and a current limiting circuit transistor, said diode being electrically connected to the base of said current limiting circuit transistor, the emitter of which transistor is electrically connected to a common conductor, and the collector of said limiting circuit transistor being electrically connected through a third resistor to the base of a transistor switch, said switch being electrically connected in parallel to the capacitor through the emitter and collector of said switch, the capacitor providing an input signal to said amplifier, the improvement comprising means to facilitate directional reversal, said reversal facilitating means comprising a field sensory resistor electrically connected to the motor field, a second resistor, and a field loss transistor having the base electrically connected to said field sensory resistor through said second resistor, the emitter of the field loss transisTor being electrically connected to a common conductor and the collector of said transistor being electrically connected to the base of the current limiting circuit transistor, wherein loss of field current in the field sensory resistor causes loss of bias for the field loss transistor, causing it to cease conduction, thereby allowing the current limiting circuit transistor to reach its conduction state, which conduction provides bias to the transistor switch, closing said switch and discharging the capacitor, thereby removing input signal from the amplifier.

Claim 7

In a speed control circuit for DC electric motors, including a speed command potentiometer electrically connected to an amplifier, a negative feedback loop, indicating motor speed, electrically connected to said amplifier, a current limiting circuit electrically connected to said amplifier, means to control armature voltage electrically connected to said amplifier, and switch means for reversing the terminal voltage polarity of the motor field, the improvement comprising a capacitor electrically connected in parallel with the motor field and across said voltage reversing switch means which capacitor acts as a bipolar discharge path for the field inductance thereby permitting the interruption of the field circuit by said switch means and limiting the rate of change in the field as seen by the armature circuit during such interruption to a level sufficiently small to permit the regulation of armature voltage.

Claim 8

In a speed control circuit for DC electric motors, including a speed command potentiometer electrically connected to an amplifier, a negative feedback loop, indicating motor speed, electrically connected to said amplifier, a current limiting circuit electrically connected to said amplifier, means to control armature voltage electrically connected to said amplifier, and switch means for reversing the terminal voltage polarity of the motor field, the improvement comprising a capacitor electrically connected in parallel with the motor field and across said voltage reversing switch means which capacitor acts as a bipolar discharge path for the field inductance thereby permitting the interruption of the field circuit by said switch means and limiting the rate of change in the field as seen by the armature circuit during such interruption to a level sufficiently small to permit the regulation of armature voltage.