Abstract: An H-bridge motor driving circuit has, between a PWM comparator and a control circuit, first and second frequency dividers for frequency-dividing, by 2, an AND gate, OR gate, and first and second and second inverters. During a first period, the first and second MOS transistors are turned on, and the second and third MOS transistors are turned off, caused a current to flow through a motor. During a next second period, the third and fourth MOS transistors are turned on, and the first and second MOS transistors are turned off, causing a regenerative current to flow through the motor. During a next third period, the MOS transistors are turned on and off in the same manner as during the first period, causing a current to flow through the motor. During a final fourth period, the first and second MOS transistors are turned on, and the third and fourth MOS transistors are turned off, caused a regenerative current to flow through the motor.

Abstract: An integrated transmission is effectively achieved within a series-excited motor by varying the number of winding turns in the field coil in relation to the speed-torque demand on the motor. At low motor speed, all of the field winding is engaged to produce the maximum available electromagnetic field, thereby increasing the motor's available torque and efficiency. When there is a high torque demand at high speed, only a portion of the field winding is engaged so that a reduced electromagnetic field is produced, thereby allowing a higher current in the motor, thereby allowing a higher torque to be produced. Thus the series motor with integrated transmission will have the same speed-torque characteristics as a system with a series motor and a conventional transmission. The integrated transmission can be implemented with relatively inexpensive relays and, if desired, by adding additional winding turns in the series field.

Abstract: A device for limiting the maximum and/or minimum speed of universal series- or compound-type electric motors. The device includes a first impedance element for limiting the maximum speed of the motor under light load (high speed) conditions to a predetermined value, and a second impedance element for limiting the minimum speed of the motor under high load (low speed) conditions. The limited maximum and minimum speeds of the motor give it operating characteristics which are similar to a shunt motor.

Abstract: A shunt element and a voltage detection circuit are connected in parallel across the armature of a universal series motor. At relatively light loads on the motor, the armature speed increases, thereby increasing the back e.m.f. of the armature. The voltage detection circuit causes the shunt element to conduct, and a shunt current flows through the field of the motor, thereby increasing the field and limiting the speed of the motor. Various embodiments are disclosed.