Speed control of electrical motors

Claim 2

A circuit arrangement for controlling in a controlled speed range, the rotational speed of an electric motor of a type whose rotational speed is dependent upon the magnitude of an applied voltage and adapting said motor in a starting speed range to a load having a variable speed-torque requirement, a source of voltage for driving said motor, said circuit arrangement comprising means for producing a first control voltage corresponding to the rotational speed of said motor and control means connected with said source of voltage for applying a second control voltage to said motor in response to said firSt control voltage, said control means including start control circuit means connected to said means for producing a first control voltage, said start control circuit means being operable in said starting speed range for establishing said second control voltage at values for causing said motor to adapt to a preselected variable speed-torque requirement, and a proportional control circuit connected to said means for producing a first control voltage, said proportional control circuit being operable in said controlled speed range to establish said second control voltage at values proportional to the speed of said motor, and selection means for controlling said second control voltage responsive to outputs from said start control circuit when operating in said starting speed range and responsive to outputs from said proportional control circuit when operating in said controlled speed range.

Claim 3

A circuit arrangement as in claim 1, wherein said starting speed range and said controlled speed range are separated by an intermediate speed range and said control means includes circuit means, operable in said intermediate speed range, for establishing said second control voltage at a constant voltage.

Claim 4

A circuit arrangement as in claim 1, wherein said starting speed range and said controlled speed range are separated by an intermediate speed range, wherein said start control circuit means includes third means for providing a third control voltage having in said starting speed range voltage-speed characteristics corresponding to said variable speed-torque requirements of said load and a constant maximum value in said intermediate and controlled speed ranges, wherein said proportional speed control circuit means includes fourth means for providing a fourth control voltage having in said controlled speed range values proportional to the speed of said motor and said constant maximum value in said intermediate and starting speed ranges, and wherein said control means further includes selection means for selecting the smaller of said third and fourth control voltages to provide said second control voltage for application to said motor.

Claim 5

A circuit arrangement according to claim 3, wherein there is provided a thyristor in circuit with said motor for obtaining phase split control of an AC voltage applied to the motor and wherein said second control voltage is coupled to the gate of said thyristor.

Claim 6

A circuit arrangement according to claim 3, wherein said selection means includes means for adjusting said speed ranges.

Claim 7

A circuit arrangement for the control of the rotational speed of an electric motor of a type whose rotational speed is dependent upon the magnitude of an applied voltage, said circuit arrangement comprising, thyristor means having gating means in circuit with said motor to obtain phase split control of voltages applied to said motor, a zener diode arranged to maintain a zener voltage from an alternating current source, an ignition capacitor connected in series with the emitter-collector path of a first transistor across said zener diode, trigger means coupled between said ignition capacitor and said thyristor for triggering said thyristor in response to a predetermined voltage across said ignition capacitor, means for generating a control voltage which varies in accordance with the speed of said motor, means including a resistor and a diode connected to apply said control voltage to directly influence the base voltage of said first transistor when the control voltage exceeds the zener voltage, a further capacitor and a further resistor connected in series across said zener diode, a second transistor, and means connecting said second transistor such that it is rendered capable of conducting when a voltage drop of given magnitude exists across said further resistor, a diode connected in parallel with said further resistor, a discharge resistor connected across said zener diode, means connecting said second transistor to influence the base voltage of saId first transistor during conduction of said second transistor, the base of said second transistor being connected to receive said control voltage, whereby in the lower speed range said second transistor becomes conductive earlier in each cycle of an applied alternating supply voltage upon the reception at its base of an increasing control voltage to become conductive and render said first transistor conductive and obtain firing of said thyristor means in a manner increasing the current flow angle thereof and wherein upon the occurrence of control voltages in excess of said zener voltage the first transistor is rendered conductive at later times in each cycle of applied alternating supply voltage by the combined direct effects of the control voltage and indirect effects thereof operating via said second transistor.

Claim 8

A circuit arrangement for the control of the rotational speed of an electric motor of a type whose rotational speed is dependent upon the magnitude of an applied voltage, said circuit arrangement comprising, thyristor means having gating means in circuit with said motor to obtain phase split control of voltages applied to said motor, a zener diode arranged to maintain a zener voltage from an alternating current source, an ignition capacitor connected in series with the emitter-collector path of a first transistor across said zener diode, trigger means coupled between said ignition capacitor and said thyristor for triggering said thyristor in response to a predetermined voltage across said ignition capacitor, means for generating a control voltage which varies in accordance with the speed of said motor, means including a resistor and a diode connected to apply said control voltage to directly influence the base voltage of said first transistor when the control voltage exceeds the zener voltage, a further capacitor and a further resistor connected in series across said zener diode, a second transistor, and means connecting said second transistor such that it is rendered capable of conducting when a voltage drop of given magnitude exists across said further resistor, a diode connected in parallel with said further resistor, a discharge resistor connected across said zener diode, means connecting said second transistor to influence the base voltage of saId first transistor during conduction of said second transistor, the base of said second transistor being connected to receive said control voltage, whereby in the lower speed range said second transistor becomes conductive earlier in each cycle of an applied alternating supply voltage upon the reception at its base of an increasing control voltage to become conductive and render said first transistor conductive and obtain firing of said thyristor means in a manner increasing the current flow angle thereof and wherein upon the occurrence of control voltages in excess of said zener voltage the first transistor is rendered conductive at later times in each cycle of applied alternating supply voltage by the combined direct effects of the control voltage and indirect effects thereof operating via said second transistor.

Claim 9

A circuit arrangement according to claim 6, wherein there is provided a full wave rectifier bridge, said zener diode being connected across the output of said rectifier bridge, the input of said bridge being connected in parallel relationship with a pair of parallel connected thyristor means, forming said thristor means, said thyristors being arranged to conduct in mutually opposite directions, said thyristors being arranged in series with said motor between a pair of input terminals whereby current will cease to flow through said zener diode in that portion of each alternating wave cycle following ignition of one of said thyristors.

Claim 10

A circuit for controlling the speed of an electric motor of the type whose speed corresponds to the magnitude of an input voltage, said circuit comprising means for producing control signals corresponding to the rotational speed of said motor and control circuit means for adjusting the input voltage to said motor in direct proportion to said control voltage in a lower motor speed and in inverse proportion to said control voltage in a higher speed range, said control circuit means comprising a proportional control circuit, a start control circuit and a selection device, said proportional control circuit and said start control circuit each being connected to receive and respond to said control signals, said proportional control circuit including means for producing outputs directing a maximum voltage to be applied to said motor in response to control signals corresponding to motor speeds up to the beginning of a speed control range and means for producing outputs directing a decreasing voltage to be applied to said motor in response to control signals corresponding to increasing motor speeds in said speed control range, said start control circuit including means for producing outputs directing an increasing voltage to be applied to said motor in response to control signals corresponding to increasing motor speeds in a low speed start and overload motor speed range and means for producing outputs directing said maximum voltage to be applied to said motor in response to control signals corresponding to motor speeds above said low speed start and overload motor speed range, said selection device including switch means operative in response to outputs from said start control circuit and said proportional control circuit to apply the lower directed voltage to said motor.

Claim 11

A circuit for controlling the speed of an electric motor of the type whose speed corresponds to the magnitude of an input voltage, said circuit comprising means for producing control signals corresponding to the rotational speed of said motor and control circuit means for adjusting the input voltage to said motor in direct proportion to said control voltage in a lower motor speed and in inverse proportion to said control voltage in a higher speed range, said control circuit means comprising a proportional control circuit, a start control circuit and a selection device, said proportional control circuit and said start control circuit each being connected to receive and respond to said control signals, said proportional control circuit including means for producing outputs directing a maximum voltage to be applied to said motor in response to control signals corresponding to motor speeds up to the beginning of a speed control range and means for producing outputs directing a decreasing voltage to be applied to said motor in response to control signals corresponding to increasing motor speeds in said speed control range, said start control circuit including means for producing outputs directing an increasing voltage to be applied to said motor in response to control signals corresponding to increasing motor speeds in a low speed start and overload motor speed range and means for producing outputs directing said maximum voltage to be applied to said motor in response to control signals corresponding to motor speeds above said low speed start and overload motor speed range, said selection device including switch means operative in response to outputs from said start control circuit and said proportional control circuit to apply the lower directed voltage to said motor.

Claim 12

A circuit arrangement according to claim 8, wherein said selection device includes a thyristor connected in series with said motor to provide voltage control to the motor by means of phase splitting, wherein each of said proportional control and said start control circuits are constructed to produce ignition impulses in the course of each applied voltage cycle, and wherein the selection device further includes circuit means operative to fire said thyristor arrangement only in response to the occurrence of the second of said ignition impulses produced in each cycle.

Claim 13

A circuit arrangement according to claim 8, wherein said switch means for applying the lower directed voltage to said motor comprises a thyristor in circuit with said motor for obtAining phase split control of the voltage applied to the motor, wherein said proportional control circuit operates to control the ignition of said thyristor, and wherein said selection device further includes means connected between said start control circuit and said proportional control circuit in a manner such that said start control circuit influences the operation of said proportional control circuit in the lower speed range.

Claim 14

A circuit arrangement according to claim 10, wherein said selection means includes means for adjusting said speed ranges.

Claim 15

A circuit according to claim 8, wherein there are provided means for supplying a maximum voltage to said motor, said start control circuit and said proportional control circuit being arranged to produce voltages less than said maximum voltage in said low speed start and overload speed range and in said speed control ranges, respectively, said selection device comprising a first and second selecting portion, said first selection portion being connected to receive said maximum voltage and the voltage output of one of said start control and proportional control circuits and to apply the lower of the two as a first selected voltage to the second selecting portion, said second selecting portion being connected to receive said first selected voltage and the voltage output from the other of said start control and proportional control circuits and to apply the lower of the two as a second selected voltage to said motor.