Control device for an electric motor

摘要

A control device for an electric motor of a cooling fan for the radiator of a motor vehicle has a control transistor connected to the motor, and an electronic control unit for controlling the speed of the motor. The control unit controls the transistor in such a manner as to limit the current flowing in the motor to a predetermined value when, by effect of the load conditions of the motor and the voltage applied to the motor, the current in the motor tends to exceed the predetermined value.

主权项

1. A control device for a direct-current electric motor, comprising:
a transistor having a first current conducting electrode coupled to a first pole of a power source, a second current conducting electrode coupled to a second pole of the power source via a winding of the motor, and a control electrode; and an electronic control unit comprising: a divider having a first input for receiving a signal of a predetermined power limit value PLIM, a second input coupled to the second current conducting electrode of the transistor, and an output providing a signal of a current limit value IPLIM by dividing the predetermined power limit value PLIM by a voltage VMMEAS at the second current conducting electrode of the transistor; a selector having a first input coupled to the output of the divider, a second input for receiving a signal of a predetermined current value ILIM, and an output providing a signal of a lesser value I*LIM of the current limit value IPLIM and the predetermined current value ILIM; a summing device having a first input coupled to the motor for receiving a signal of a current value IMMEAS in the motor, a second input coupled to the output of the selector, and an output providing a signal of a current error ei=I*LIM−IMMEAS; a control device having an input coupled to the output of the summing device and an output coupled to the control electrode of the transistor for controlling the transistor in response to the signal of the current error ei so as to limit the current in the motor to the lesser value I*LIM to limit the current in the motor to the predetermined current value when the current in the motor tends to exceed the predetermined current value, and limit the power consumption of the motor to the predetermined power limit value when the power consumption tends to exceed the predetermined power limit value by effect of increasing of the voltage applied to the motor; and wherein the current limit value IPLIM varies with the voltage VMMEAS.