System and method for increasing the efficiency of alternating current induction motors

• US 5,723,966 A
• Filed: 08/23/1996
• Issued: 03/03/1998
• Est. Priority Date: 08/23/1996
• Status: Expired due to Fees

• Current Assignee: Current Technologies LLC (Pattern Inc.)
• Original Assignee: Current Technologies LLC (Pattern Inc.)
• Inventors: Coombs, David Maxwell, Straka, Richard Stephen
• Primary Examiner(s): Ro, Bentsu
• Application Number:
  US08/702,267
• Time in Patent Office: 557 Days
• Field of Search: 318/650, 318/727, 318/729, 318/805, 318/809
• US Class Current: 318/650
• CPC Class Codes: G05F 1/70 Regulating power factor; Regulating reactive current or power
• CPC Class Codes: H02P 23/26 Power factor control [PFC]
• CPC Class Codes: Y02P 80/10 Efficient use of energy, e.g. using compressed air or pressurized fluid as energy carrier

Abstract

A system for increasing the efficiency of single and multi-phase induction motors. The system is comprised of a microcontroller which combines a time when the AC line current reaches zero amps with a time when AC line voltage to the AC motor reaches zero volts and with a digital measurement provided by an A/D converter to determine a servo error. The servo error determines whether the A/C motor needs more or less power. The microprocessor provides a control signal to a switching means to supply the minimum power required based on the servo error.

Claims

1. A system for increasing efficiency of an AC motor, comprising, in combination:

switching means coupled to said AC motor for controlling power supplied to said AC motor;

timer means coupled to said AC motor for monitoring a time when AC line voltage to said AC motor reaches zero volts;

A/D converter means coupled to said timer means for monitoring a time when AC line current to said AC motor reaches zero amps and for converting an AC open circuit voltage across said switching means from an analog measurement to a digital measurement, said digital measurement being indicative to power actually needed by said AC motor; and

microcontroller means coupled to said timer means, to said A/D converter means and to said switching means for combining said time when AC line current reaches zero amps with said time when AC line voltage to said AC motor reaches zero volts and with said digital measurement provided by the A/D converter means to determine a servo error, for determining if said AC motor needs more power based on said servo error, for determining if said AC motor needs less power based on said servo error, and for providing a control signal to said switching means to supply the minimum power required.

2. The system of claim 1 further comprising memory means coupled to said microcontroller means for storing control constants to a specific model of said AC motor for optimization of said control signal from said microcontroller means to said switching means.

3. The system of claim 1 further comprising switch driver means coupled to said switching means for optically isolating said control signal from said AC line current and for amplifying said control signal to said switching means.

4. The system of claim 2 further comprising programmer means coupled to said switching means for programming said memory means with said control constants for a plurality of said AC motors wherein each of said AC motors utilizes different values of said control constants.

5. The system of claim 2 wherein said microcontroller means comprises:

power factor measuring means coupled to said A/D converter means and to said timer means for measuring power factors of said AC motor;

motor signal means coupled to said A/D converter means for providing a motor signal based on said digital measurement which is indicative to said power actually needed by said AC motor;

command signal generation means coupled to said power factor measuring means and to said memory means for calculating a command signal;

differencing means coupled to said command signal generation means and to said motor signal means for generating said servo error signal by differencing said command signal with said motor signal;

amplifier means coupled to said differencing means for progressively amplifying said servo error signal;

integrating means coupled to said amplifier means for mathematically integrating said progressively amplified servo error signal; and

duty cycle means coupled to said integrating means and to said switching means for setting a duty cycle value based on said mathematically integrated progressively amplified servo error signal and for activating said switching means based on said duty cycle value.

6. The system of claim 4 wherein said programmer means comprises;

data source means for providing said control constants;

data translation means coupled to said data source means for translating and transferring a bi-directional data stream between said memory means and said data source means and for reading a data output from said memory means by monitoring and interpreting a state of said switching means; and

switchable current source means coupled to said data translation means and to said switching means for writing a data input to said memory means by controlling said switchable current source means in response to said data source means and for providing a direction of current to said switching means to change a state of said switching means to an open condition to allow said microcontroller means to read and translate said data input for said memory means.

7. The system of claim 6 wherein said microcontroller means further activates said switching means to achieve clock synchronization between said microcontroller means, said memory means and said programmer means.

8. The system of claim 4 further comprising selection means coupled between said programmer means and said switching means for changing said system from a run state to a programming state.

9. A system for increasing efficiency of an AC motor, comprising, in combination:

switching means coupled to said AC motor for controlling power supplied to said AC motor;

timer means coupled to said AC motor for monitoring a time when AC line voltage to said AC motor reaches zero volts;

A/D converter means coupled to said timer means for monitoring a time when AC line current to said AC motor reaches zero amps and for converting an AC open circuit voltage across said switching means from an analog measurement to a digital measurement, said digital measurement being indicative of power actually needed by said AC motor;

microcontroller means coupled to said timer means, to said A/D converter means and to said switching means for combining said time when AC line current reaches zero amps with said time when AC line voltage to said AC motor reaches zero volts and with said digital measurement provided by the A/D converter means to determine a servo error, for determining if said AC motor needs more power based on said servo error, for determining if said AC motor needs less power based on said servo error, and for providing a control signal to said switching means to supply the minimum power required, said microcontroller means comprising;

power factor measuring means coupled to said A/D converter means and to said timer means for measuring power factors of said AC motor;

motor signal means coupled to said A/D converter means for providing a motor signal based on said digital measurement which is indicative of said power actually needed by said AC motor;

command signal generation means coupled to said power factor measuring means for calculating a command signal;

differencing means coupled to said command signal generation means and to said motor signal means for generating a servo error signal by differencing said command signal with said motor signal;

amplifier means coupled to said differencing means for progressively amplifying said servo error signal;

integrating means coupled to said amplifier means for mathematically integrating said progressively amplified servo error signal; and

duty cycle means coupled to said integrating means and to said switching means for setting a duty cycle value based on said mathematically integrated progressively amplified servo error signal and for activating said switching means based on said duty cycle value;

memory means coupled to said microcontroller means for storing control constants to a specific model of said AC motor for optimization of said control signal from said microcontroller means to said switching means;

switch driver means coupled to said switching means for optically isolating said control signal from said AC line current and for amplifying said control signal to said switching means; and

programmer means coupled to said switching means for programming said memory means with said control constants for a plurality of said AC motors wherein each of said AC motors utilizes different values of said control constants, said programmer means comprising;

data source means for providing said control constants;

data translation means coupled to said data source means for translating and transferring a bi-directional data stream between said memory means and said data source means and for reading a data output from said memory means by monitoring and interpreting a state of said switching means; and

switchable current source means coupled to said data translation means and to said switching means for writing a data input to said memory means by controlling said switchable current source means in response to said data source means and for providing a direction of current to said switching means to change a state of said switching means to an open condition to allow said microcontroller means to read and translate said data input for said memory means; and

selection means coupled between said programmer means and said switching means for changing said system from a run state to a programming state.

10. A method of providing a system for increasing efficiency of an AC motor, comprising, the steps of:

providing switching means coupled to said AC motor for controlling power supplied to said AC motor;

providing timer means coupled to said AC motor for monitoring a time when AC line voltage to said AC motor reaches zero volts;

providing A/D converter means coupled to said timer means for monitoring a time when AC line current to said AC motor reaches zero amps and for converting an AC open circuit voltage across said switching means from an analog measurement to a digital measurement, said digital measurement being indicative to power actually needed by said AC motor; and

providing microcontroller means coupled to said timer means, to said A/D converter means and to said switching means for combining said time when AC line current reaches zero amps with said time when AC line voltage to said AC motor reaches zero volts and with said digital measurement provided by the A/D converter means to determine a servo error, for determining if said AC motor needs more power based on said servo error, for determining if said AC motor needs less power based on said servo error, and for providing a control signal to said switching means to supply the minimum power required.

11. The method of claim 10 further comprising the step of providing memory means coupled to said microcontroller means for storing control constants to a specific model of said AC motor for optimization of said control signal from said microcontroller means to said switching means.

12. The method of claim 10 further comprising the step of providing switch driver means coupled to said switching means for optically isolating said control signal from said AC line current and for amplifying said control signal to said switching means.

13. The method of claim 11 further comprising the step of providing programmer means coupled to said switching means for programming said memory means with said control constants for a plurality of said AC motors wherein each of said AC motors utilizes different values of said control constants.

14. The method of claim 11 wherein the step of providing said microcontroller means comprises the steps of:

providing power factor measuring means coupled to said A/D converter means and to said timer means for calculating power factors of said AC motor;

providing motor signal means coupled to said A/D converter means for providing a motor signal based on said digital measurement which is indicative to said power actually needed by said AC motor;

providing command signal generation means coupled to said power factor measuring means and to said memory means for calculating a command signal;

providing differencing means coupled to said command signal generation means and to said motor signal means for generating a servo error signal by differencing said command signal with said motor signal;

providing amplifier means coupled to said differencing means for progressively amplifying said servo error signal;

providing integrating means coupled to said amplifier means for mathematically integrating said progressively amplified servo error signal; and

providing duty cycle means coupled to said integrating means and to said switching means for setting a duty cycle value based on said mathematically integrated progressively amplified servo error signal and for activating said switching means based on said duty cycle value.

15. The method of claim 13 wherein the step of providing said programmer means comprises the steps of;

providing data source means for providing said control constants;

providing data translation means coupled to said data source means for translating and transferring a bi-directional data stream between said memory means and said data source means and for reading a data output from said memory means by monitoring and interpreting a state of said switching means; and

providing switchable current source means coupled to said data translation means and to said switching means for writing a data input to said memory means by controlling said switchable current source means in response to said data source means and for providing a direction of current to said switching means to change a state of said switching means to an open condition to allow said microcontroller means to read and translate said data input for said memory means.

16. The method of claim 15 wherein the step of providing said microcontroller means further comprises the step of providing activation of said switching means to achieve clock synchronization between said microcontroller means, said memory means and said programmer means.

17. The method of claim 13 further comprising the step of providing selection means coupled between said programmer means and said switching means for changing said system from a run state to a programming state.