System and method for speed control and stall protection combination for electric motors such as in engine cooling applications

A speed control and stall protection system for an electric DC brush motor, the system comprising:

• a DC brush motor,
• at least one relay connected between the motor and a power supply,
• means for generating a signal indicative of a speed of the motor, and
• means for controlling speed and protecting the motor constructed and arranged to receive 1) the signal from the speed sensing circuit and 2) a control signal input for operating the at least one relay to control operation of the motor,
• wherein, when a stall condition is determined based on the signal from the means for generating a signal indicative of a speed of the motor, the means for controlling speed and protecting the motor controls the at least one relay to disconnect power to the motor, and
• wherein the motor is a dual speed motor and a first relay is provided together with a series resistor for operating the motor at a low speed and a second relay is provided for operating the motor at a speed greater than the low speed, the means for controlling speed and protecting the motor being constructed and arranged to receive the control signal input in the form of a speed control signal to selectively activate the first and second relays to control speed of the motor and to inactivate the first and second relays to disconnect power to the motor.

A method of controlling speed and protecting during a stall condition, the method including the steps of:

• providing a permanent magnet DC brush motor,
• providing at least one relay connected between the motor and a power supply,
• controlling the at least one relay to operate the motor,
• determining a speed of the motor, and
• comparing the determined speed of motor with a threshold value and if the determined speed is below the threshold value, controlling the at least one relay to disconnect power to the motor,
• wherein the motor is a dual speed motor and a first relay is provided together with a series resistor for operating the motor at a low speed and a second relay is provided for operating the motor at a speed greater than the low speed, the step of controlling the at least one relay to operate the motor includes selectively activating the first and second relays to control the speed of the motor, and the step of controlling the at least one relay to disconnect power to the motor includes inactivating both the first and second relays.