METHOD, SYSTEM, AND APPARATUS FOR CONTROLLING AN ELECTRIC MOTOR
First Claim
1. A system, comprising:
- a power supply coupled to a phase detector;
the phase detector having a first phase detector output and a second phase detector output, wherein the first phase detector output is synchronized to a zero crossing of a motor current of the motor and a second phase detector output is synchronized to a zero crossing of a line voltage of the power supply;
a digital microprocessor coupled between the first and second phase detector outputs and a rectifier, wherein the digital microprocessor is configured to sense a first time at which a phase of the motor voltage is crossing zero;
sense a second time at which a phase of the motor current is crossing zero;
determine the difference in time between the first and second times;
use the difference in time to calculate a phase lag of the motor; and
use the phase lag to calculate a firing time of the rectifier.
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Accused Products
Abstract
The present invention provides systems and methods for power factor control of a motor. A phase detector uses a line voltage of a power supply and a motor terminal voltage of a motor. The output of the phase detector is synchronized to a zero crossing of the motor current of the motor and a zero crossing of the line voltage. A digital microprocessor connected between the output of the phase detector and a rectifier driver senses a first time at which a phase of the motor voltage is crossing zero volts and a second time at which a phase of the motor current is crossing zero current. The digital microprocessor calculates the difference in time between the first and second times and uses the difference in time to calculate a phase lag of the motor. The digital microprocessor uses the phase lag to calculate a firing time of a rectifier to command power efficiently to the motor.
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Citations
20 Claims
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1. A system, comprising:
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a power supply coupled to a phase detector;
the phase detector having a first phase detector output and a second phase detector output, wherein the first phase detector output is synchronized to a zero crossing of a motor current of the motor and a second phase detector output is synchronized to a zero crossing of a line voltage of the power supply;
a digital microprocessor coupled between the first and second phase detector outputs and a rectifier, wherein the digital microprocessor is configured to sense a first time at which a phase of the motor voltage is crossing zero;
sense a second time at which a phase of the motor current is crossing zero;
determine the difference in time between the first and second times;
use the difference in time to calculate a phase lag of the motor; and
use the phase lag to calculate a firing time of the rectifier. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A system, comprising:
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a power supply coupled to a phase detector;
the phase detector having a first phase detector input, a second phase detector input, and a phase detector output, wherein the phase detector includes the second phase detector input is coupled to a first inverting input of a first operational amplifier via a first voltage divider and the first phase detector input is coupled to a first non-inverting input of the first operational amplifier via a second voltage divider and a second inverting input of a second operational amplifier via a third voltage divider, wherein a first amplifier output of the first operational amplifier is synchronized to a zero crossing of the motor current and a second amplifier output of the second operational amplifier is synchronized to a zero crossing of the line voltage;
a digital microprocessor coupled between the phase detector output comprising the first and second amplifier outputs and a rectifier driver, wherein the digital microprocessor determines a phase lag of the current and voltage of the motor by calculating the time difference between a switching state of the first operational amplifier and a switching state of the second operational amplifier in order to control the firing of the rectifier driver. - View Dependent Claims (9, 10, 11, 12, 13)
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14. A method for control of a motor, comprising the steps of:
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using a digital microprocessor, sensing a first time at which a phase of the motor voltage is crossing zero;
using a digital microprocessor, sensing a second time at which a phase of the motor current is crossing zero;
using a digital microprocessor, determining the difference in time between the first and second times;
using a digital microprocessor, using the difference in time to calculate a phase lag of the motor; and
using a digital microprocessor, using the phase lag to calculate a firing time of a rectifier. - View Dependent Claims (15, 16, 17, 18, 19, 20)
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Specification