Abstract A reversible D.C. motor system is energized from an A.C. source and provided with a reversible field excitation system for controlling the direction of rotation of the motor. The field excitation is provided by a field exciting winding energized by a half-wave rectifier arrangement, the output of which is selectable to energize the field winding by either positive or negative half-wave rectified A.C. with a capacitance connected across the winding to smooth out the half-wave energization and energize the winding from the capacitance when not energized by the rectified half-wave A.C. whereby a continuous current energization is provided to the field winding during normal operation. A threshold voltage breakdown means is connected reverse biased across the field winding and has a voltage breakdown threshold which is a predetermined percent above the normal maximum peak half-wave A.C. supplied by the rectifier, so that on cessation, for any reason, of supply of half-wave rectified, A.C. from the rectifier, such as during a deenergization of the field prior to reversal thereof for reverse motor operation, the magnetic inductively stored energy of the field is rapidly dissipated in the threshold breakdown means during breakdown thereof after the field winding has discharged into the capacitance to the point of having raised its voltage to the threshold value of the breakdown means. Operation of the motor is controlled manually by switching means having forward and reverse positions, and an intermediate braking position. In the latter position, dynamic braking of the armature is used to expedite its stoppage. Protective interlock circuits prevent energization of the armature when the field winding is deenergized and prevent applying reverse energization to the field winding before the motor has stopped. Other protective circuits prevent restarting of the motor until it is fully stopped and provide rapid deenergization of the armature under predetermined excess armature current conditions and deenergize the entire system should the excess current condition continue beyond a predetermined time.
In a control system for a shunt D.C. motor having a field excitation winding, a reversible excitation system for said field winding comprising: A. capacitance means connected in parallel with said winding; B. means including A.C. rectifying means for selectively supplying positive half-wave rectified A.C. and negative halfwave rectified A.C. to said parallel connected field winding and capacitance means for selectively reversibly exciting said motor for reversible operation thereof; and C. bi-directional threshold voltage breakdown means connected across said field winding and capacitance means for dissipating inductively stored energy of the field winding after removal of the half-wave rectified A.C. energization from the field winding, said threshold voltage breakdown means having a breakdown voltage threshold above the normal applied half-wave rectified A.C. from said rectifying means.
Claim 2
Dependent Claim
126 words
In a control system for a shunt D.C. motor having a field excitation winding, a reversible excitation system for said field winding comprising: A. capacitance means connected in parallel with said winding; B. means including A.C. rectifying means for selectively supplying positive half-wave rectified A.C. and negative halfwave rectified A.C. to said parallel connected field winding and capacitance means for selectively reversibly exciting said motor for reversible operation thereof; and C. bi-directional threshold voltage breakdown means connected across said field winding and capacitance means for dissipating inductively stored energy of the field winding after removal of the half-wave rectified A.C. energization from the field winding, said threshold voltage breakdown means having a breakdown voltage threshold above the normal applied half-wave rectified A.C. from said rectifying means.
Claim 3
Dependent Claim
46 words
A field excitation system as defined in claim 1 wherein said be-directional threshold voltage breakdown means comprises a full wave rectifier bridge having input terminals connected across said field exciting winding, and a threshold voltage breakdown device connected reverse-biased across the output terminals of the bridge.
Claim 4
Dependent Claim
37 words
The combination as in claim 1 wherein there is means for preventing reversal of the energization applied to said field winding when changing from one motor rotation direction to the opposite direction until the motor has stopped.
Claim 5
Dependent Claim
43 words
The combination as in claim 3 wherein there is a dynamic braking circuit and means for rendering it operative with said motor, and wherein said means for preventing the reversal of field energization is responsive to a condition of said dynamic braking circuit.