System and method for commutating a motor
First Claim
1. A method for adjusting a rotational speed of a rotor in a polyphase motor from a first speed towards a second, faster speed when the motor is commutating according to a commutation scheme at a first commutation phase angle, the method comprising:
- determining said first commutation angle utilizing a first back EMF voltage detected in said motor;
commutating said motor when the first back EMF voltage is detected in said motor;
selecting an advanced phase angle relative to the first commutation phase angle for commutating the motor; and
adjusting the commutation scheme to be commutating at the advanced phase angle bycalculating a rate of change of back EMF in the motor at the first speed using a back EMF constant of the motor;
determining a second back EMF voltage according to the rate of change in respect of the advance phase angle; and
adjusting the commutation scheme to commutate when the second back EMF voltage is observed,whereby the rotational speed of the rotor increases from the first speed towards the second speed as the motor is commutating at the advanced phase angle.
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Abstract
A method for adjusting a rotational speed of a rotor in a polyphase motor from a first speed towards a second, faster speed when the motor is commutating according to a commutation scheme at a first commutation phase angle is described. The method comprises selecting an advanced phase angle relative to the first commutation phase angle for commutating the motor; and adjusting the commutation scheme to be commutating at the advanced phase angle, so that the rotational speed of the rotor increases from the first speed towards the second speed as the motor is commutating at the advanced phase angle. A system implementing the method is also described.
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Citations
17 Claims
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1. A method for adjusting a rotational speed of a rotor in a polyphase motor from a first speed towards a second, faster speed when the motor is commutating according to a commutation scheme at a first commutation phase angle, the method comprising:
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determining said first commutation angle utilizing a first back EMF voltage detected in said motor; commutating said motor when the first back EMF voltage is detected in said motor; selecting an advanced phase angle relative to the first commutation phase angle for commutating the motor; and adjusting the commutation scheme to be commutating at the advanced phase angle by calculating a rate of change of back EMF in the motor at the first speed using a back EMF constant of the motor; determining a second back EMF voltage according to the rate of change in respect of the advance phase angle; and adjusting the commutation scheme to commutate when the second back EMF voltage is observed, whereby the rotational speed of the rotor increases from the first speed towards the second speed as the motor is commutating at the advanced phase angle. - View Dependent Claims (2, 3, 4, 5, 6, 7, 9, 10, 11, 12, 13)
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8. A system for adjusting a rotational speed of a rotor in a polyphase motor from a first speed towards a second, faster speed when the motor is commutating according to a commutation scheme at a first commutation phase angle, the system comprising:
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the motor; and a motor controller for selecting an advanced phase angle relative to the first commutation phase angle for commutating the motor; for calculating a rate of change of back EMF in the motor at the first speed using a back EMF constant of the motor; for determining a second back EMF voltage for the motor according to the rate of change in respect of the advanced phase angle. for adjusting the commutation scheme to commutate the motor when the second back EMF voltage is observed at the advanced phase angle so that the rotational speed of the rotor increases from the first speed towards the second speed as the motor commutates to the advanced phase angle; and wherein the first commutation phase angle is determined with respect to a first back EMF voltage; and the commutation scheme commutates when the first back EMF voltage is detected in the motor.
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14. A motor controller for adjusting a rotational speed of a rotor in a polyphase motor from a first speed towards a second, faster speed when the motor is commutating according to a commutation scheme at a first commutation phase angle, the controller comprising:
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a first module to select an advanced phase angle relative to the first commutation phase angle for commutating the motor; a second module to calculate a rate of change of back EMF in the motor at the first speed using a back EMF constant of the motor; a third module to determine a second back EMF voltage for the motor according to the rate of change in respect of the advanced phase angle; and a fourth module to adjust the commutation scheme to commutate the motor when the second back EMF voltage is observed at the advanced phase angle so that the rotational speed of the rotor increases from the first speed towards the second speed as the motor commutates to the advanced phase angle, wherein the first commutation phase angle is determined with respect to a first back EMF voltage; and the commutation scheme commutates when the first back EMF voltage is detected in the motor. - View Dependent Claims (15, 16, 17)
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Specification