Speed control system for electric motor

A method of controlling the speed of an electric motor in response to load variations on the motor output, comprising the steps of providing a signal related to a desired motor speed, sensing motor voltage and generating a signal related thereto, sensing motor current and generating a signal related thereto, combining the motor voltage-related signal and the motor current-related signal to produce a signal related to motor speed, combining the motor speed-related signal and the desired motor signal to generate a switched error signal for controlling the speed of the motor by coupling the motor speed-related signal to a first base of a unijunction transistor and coupling the desired motor speed-related signal to a second base of the unijunction transistor, the unijunction transistor comparing the signal at its first base with the signal at its second base and switching from a non-conducting state to a full conducting state and from the full conducting state to the non-conducting state in response to the comparison to generate the switched error signal at its emitter.

A method of controlling the speed of an electric motor comprising the steps of sensing motor voltage and generating a signal related thereto, sensing motor current and generating a signal related thereto, summing the motor voltage-related and motor current-related signals, coupling the sum signal to a first base of a unijunction transistor, providing a signal related to a desired motor speed, coupling the desired motor speed related signal to a second base of the unijunction transistor to establish a reference level at the second base of the unijunction transistor, the unijunction transistor selectively switching from a full conducting to a non-conducting state and from the non-conducting to the full conducting state based upon the relative levels of the signals at its first and second bases and thereby generating at its emitter a switched error signal for controlling the motor speed.

A speed control for an electric motor comprising first circuit means coupling the motor to a source of electrical power, second circuit means providing a signal related to a desired motor speed, third circuit means for sensing motor voltage and generating a signal related thereto, fourth circuit means for sensing motor current and generating a signal related thereto, means for combining the motor voltage signal and the motor current signal to produce a motor speed-related signal, an electronic switch having first and second inputs and an output, means for coupling the combining means to the first input, means for coupling the second circuit means to the second input, the electronic switch comparing the motor speed-related signal coupled to its first input with the desired motor speed-related signal coupled to its second input and switching from a non-conducting state to a full conducting state and from the full conducting state to the non-conducting state based upon the comparison to generate a switched error signal at its output for controlling the speed of the motor, and means for coupling the output of the electronic switch to the first circuit means, the first circuit means including means responsive to the switched error signal to switch current into the motor windings in response thereto to vary the speed of the motor.

A method of controlling the speed of an electric motor in response to load variations on the motor output comprising the steps of providing a signal related to a desired motor speed, sensing motor voltage and generating a signal related thereto, sensing motor current and generating a signal related thereto, combining the motor voltage-related signal and the motor current-related signal to produce a signal related to motor speed, combining the motor speed-related signal and the desired motor speed signal to generate a switched error signal by coupling the motor speed-related signal to a first input of an electronic switch and coupling the desired motor speed-related signal to a second input of the electronic switch, the electronic switch comparing the signal at its first input with the signal at its second input and switching from a non-conducting state to a full conducting state and from the full conducting state to the non-conducting state in response to the comparison to generate the switched error signal at an output, coupling the switched error signal to the motor, and utilizing the switched error signal to control the speed of the motor.

A method of controlling the speed of an electric motor comprising the steps of sensing motor voltage and generating a signal related thereto, sensing motor current and generating a signal related thereto, summing the motor voltage-related and the motor current-related signals, coupling the summed signal to a first input of an electronic switch, providing a signal related to a desired motor speed, coupling the desired motor speed-related signal to a second input of the electronic switch to establish a reference level at the second input, the electronic switch selectively switching based upon the relative levels of the signals at its first and second inputs from a non-conducting state for a full conducting state to generate a switched error signal at an output of the electronic switch and coupling the switched error signal to the motor to control the speed of the motor.