A DC motor control circuit for providing improved starting and stopping control is provided. The control circuit includes a DC motor that is driven in response to an operating voltage applied thereto. A shunting element is adapted to define a current path in parallel with the DC motor to selectively shunt the operating voltage applied to the DC motor. A DC supply is provided for producing a DC signal, and a constant voltage supply circuit is coupled intermediate the DC supply and the parallel connection of the shunt element and DC motor to selectively apply a constant operating voltage to the DC motor. A control circuit is provided for coincidentally applying a control signal to the constant voltage circuit and to the shunt element to effect a coincident shunting of the operating voltage applied to the DC motor and a cutting-off of the application of the operating voltage to the DC motor.
A controller for a vehicle fuel pump electric motor is connected to one or more vehicle sensors for sensing fuel flow demand and pulse width modulating the motor to control the speed. A fuel demand sensor and a triangle generator are connected to a summing controller for generating a pulse width modulated control signal to a driver. The driver has a pair of outputs for generating a pair of complementary pulse width modulated switch signals to a pair of switches whereby the switches are switched on and off alternately. One of the switches is connected in series between a power supply and the motor armature and the other switch is connected across the armature. A crash sensor, such as an inertia switch, is connected to the summing controller for terminating pulse width modulation in the event of a crash. The switch connected across the armature can be turned on to short circuit the armature and quickly stop the motor in the event of a crash.
A circuit for operating an electric motor (10) has a triac (24) that is parallel to the electric motor (10). The triac (24) is acted upon by a first control signal (28) that is dependent on the voltage present at a first connection (11) of the electric motor (10). The triac (24) is further acted on by a second control signal (22) that is emitted as a braking signal by a motor-control circuit (19). The circuit of the invention, which includes a semiconductor component (24), permits both a braking of the electric motor (10) and the damping of an inductive voltage peak during the switch-off process of the electric motor (10). The damping of the inductive voltage peak is also assured after the separation of the voltage from an energy source (16).
Arrangement for winding of an electric cable which arrangement comprises a rotatable drum from which the cable is arranged to be wound off manually, and an electric motor (M) arranged to be connected to a first circuit for driving the drum in the winding direction and arranged to be rotated by the drum during unwinding of the cable. A second circuit (M,1,3,4) comprises besides the motor (M) also a contact means (1) arranged to be closed when the motor (M) is inoperative. During unwinding of the cable from the drum the motor generates a braking moment which increases with the speed of rotation of the motor. The second circuit preferably comprises a voltage dependent switch (3), preferably a Zener-diode, which is arranged to be closed when the voltage generated by the motor (M) during the unwinding exceeds a value corresponding to a predetermined speed of rotation of the drum and, as a consequence, of the motor.
The device for controlling the rotation speed of electric motors comprises an adjustable frequency generator (2) generating an output signal (s.sub.1) having a frequency which can be adjusted in relation to the desired speed (v.sub.d), a pulse generator (3) having a pre-determined period controlled by the adjustable frequency generator in such a way as to generate a control signal (s.sub.2) comprising a series of pulses at the adjustable frequency set by the frequency generator (2). The control signal (s.sub.2) is provided to a control unit (5) for the motor (6) whose rotation speed is to be controlled. The control unit thus provides a supply to the motor (6) corresponding to the control signal pulses. FIG. 1.
A power source circuit supplies positive and negative voltages to a DC motor. A first switching element is provided in a path for supplying a positive voltage from the power source circuit. A second switching element is provided in a path for supplying a negative voltage from the power source circuit. A driving circuit outputs an ON/OFF control signal for setting the first and second switching elements to opposite switching states in response to a forward/reverse rotation instruction for the DC motor. The driving circuit also outputs an OFF control signal for setting the first and second switching elements into the OFF state in response to a rotation interruption instruction. A short-circuiting circuit short-circuits both ends of the DC motor to brake the DC motor and interrupt the rotation thereof in response to the rotation interruption instruction.
