Abstract: A direct current motor for use in a closed-loop control system is disclosed that produces a time varying signal indicative of a position of the motor. An embodiment of the motor includes a rotating commutator having a plurality of slots, a plurality of windings, the number of windings corresponding to one more than the number of slots of the commutator, and a plurality of brushes that are configured so that application of a direct current voltage across the brushes causes the commutator to rotate.A closed-loop control system is also disclosed that includes a direct current voltage source, a direct current motor in accordance with the present, a motor position signal source that generates a motor position signal for rotating the shaft of the direct current motor to a desired position, and a feedback circuit that corrects for any error in the desired position of the shaft of the direct current motor.

Abstract: A direct current motor for use in a closed-loop control system is disclosed that includes a rotating commutator having a plurality of slots, a plurality of windings, the number of windings that conduct current corresponding to one less than the number of slots of the commutator, and a plurality of brushes that are configured so that application of a direct current voltage across the brushes results in a current flow in at least one of the windings which causes the commutator to rotate. Continuous application of the direct current voltage across the brushes causes the current to flow in a varying number of the current conducting windings as the commutator continues to rotate, the number periodically varying from all of the current conducting windings to the at least one current conducting winding.

Abstract: A circuit for changing the poles of a rotor of a synchronous machine having contact brushes in operative connection with first and second slip rings includes a switch for reversibly connecting the contact brushes to an electrical current source, reversible pole coils operatively connected to one of the slip rings and connected through a first diode to a circuit portion which is formed by irreversible pole coils, and by a second diode and a third diode, and which is operatively connected with the other of the slip rings, and a circuit branch including a fourth diode having a polarity reversed with respect to the polarities of the first, second and third diodes. One terminal of the fourth diode is connected between the reversible pole coils and the first diode and the other terminal of the fourth diode is connected between the irreversible pole coils and the second diode.

Abstract: An arrangement to provide variation of the speed or other operating parameters of an electrical machine without connection to the rotor. The machine is of the induction type having a winding in separate parts to create a flux movable in the air-gap different speeds by the alteration of current in a part of the winding. In one example the current is altered by a variable impedance connected to one winding part, the other part being connected to an electrical supply.Another example, FIG. 6, shows two machines (NM.sub.1, NM.sub.2) arranged to drive a rail vehicle through smooth rail wheels attached to the machine rotor axles. A single, variable-frequency, inverter (NI) drives both machines and is connected to part (MP) of each machine winding. Other parts (AP) of each machine winding are connected together by a link (NC). In operation power (real or reactive) is transferred between the machines along the link to equalize the torque of the machines.