Apparatus and method to generate braking torque in an AC drive
First Claim
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1. A drive braking control to produce counter-rotating torque in an AC motor, comprising:
- a converter supplying multiple frequency AC power to said motor;
said control providing a normal frequency output to said motor at a first frequency;
said control simultaneously providing a second loss-inducing frequency output to said motor to produce a level of desired braking to the motor speed; and
said second frequency being different than said first frequency.
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Abstract
A device and control method to produce braking torque counter to motor rotation. A converter supplies multiple frequency AC power to the motor. A first frequency is supplied at the normal operating frequency/speed. A second frequency, different from the normal operating frequency, is supplied to produce braking torque. The level of braking can be controlled to generally consume some or all of the braking in the device or motor. More than one braking frequency may be utilized. In addition, the relationship between the normal and braking frequency(s) can be maintained to limit motor pulsation.
109 Citations
42 Claims
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1. A drive braking control to produce counter-rotating torque in an AC motor, comprising:
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a converter supplying multiple frequency AC power to said motor;
said control providing a normal frequency output to said motor at a first frequency;
said control simultaneously providing a second loss-inducing frequency output to said motor to produce a level of desired braking to the motor speed; and
said second frequency being different than said first frequency. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21)
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22. A method of braking to produce counter-rotating torque in an AC motor, comprising:
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providing a normal frequency output to said motor at a first frequency;
simultaneously providing a second loss-inducing frequency output to said motor to produce braking torque to the motor; and
said second frequency being provided at a frequency different than said first frequency. - View Dependent Claims (23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42)
providing a converter to supply said normal and said loss-inducing frequencies; and
providing a controller to control the amplitudes of voltages of said normal and said loss-inducing frequencies to maximize the counter-rotating torque, while generally matching induced losses to absorbed energy, and while generally not exceeding current and voltage capabilities of said converter.
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30. The method of claim 24 further comprising introducing the loss-inducing commands in a rotating coordinate system, using a desired torque-pulsation frequency generally corresponding to a given torque-pulsation, so that the loss-inducing frequency actually applied to the motor automatically varies with the speed of the motor to maintain the difference between the normal and loss-inducing frequencies equal to the desired torque-pulsation frequency.
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31. The method of claim 22 further comprising controlling the difference between said first frequency and said second frequency at a previously determined value.
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32. The method of claim 31 further comprising:
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providing a converter to supply said normal and said loss-inducing frequencies; and
providing a controller to control the amplitudes of the voltages of said normal and said loss-inducing frequencies to maximize the counter-rotating torque, while matching induced losses to absorbed energy at a value to generally not exceed current and voltage capabilities of said converter.
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33. The method of claim 31 wherein further comprising maintaining combined output voltages and currents from said first and second frequencies below preset limits.
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34. The method of claim 33 further comprising controlling amplitude of the second frequency to generally consume the energy absorbed during braking.
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35. The method of claim 22 further comprising maintaining combined output voltages and currents from said first and second frequencies below preset limits.
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36. The method of claim 22 further comprising controlling the amplitude of the second frequency to generally consume the energy absorbed during braking.
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37. The method of claim 36 further comprising maintaining continuous estimation of motor speed during braking to permit a prompt return to positive torque production.
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38. The method of claim 37 further comprising:
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providing a converter to supply said normal and said loss-inducing frequencies; and
providing a controller to control the amplitudes of voltages of said normal and said loss-inducing frequencies to maximize the counter-rotating torque, while generally matching induced losses to absorbed energy, and while generally not exceeding the current and voltage capabilities of said converter.
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39. The method of claim 37 further comprising introducing the loss-inducing commands in a rotating coordinate system, using a desired torque-pulsation frequency generally corresponding to a given torque-pulsation, so that the loss-inducing frequency actually applied to the motor automatically varies with the speed of the motor to generally maintain the difference between the normal and loss-inducing frequencies generally equal to the desired torque-pulsation frequency.
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40. The method of claim 22 further comprising employing two or more loss-inducing frequencies simultaneously.
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41. The method of claim 22 further comprising continuous estimation of motor speed during braking to permit a prompt return to positive torque production.
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42. The method of claim 22 further comprising introducing loss-inducing commands in a rotating coordinate system, using a desired torque-pulsation frequency generally corresponding to a given torque-pulsation, so that the loss-inducing frequency actually applied to the motor automatically varies with the speed of the motor to maintain the difference between the normal and loss-inducing frequencies generally equal to the desired torque-pulsation frequency.
Specification