Method for making a motor quieter

Abstract

The method is for making an electric motor more efficient by iteratively changing when a processor sends activation signals to transistors to minimize a current required to rotate a rotor at a constant rotational speed. The method is also for changing a rotational direction of the rotor by switching the order in which activation signals are sent to the transistors.

I claim: 
     
         1 . A method for making an electric motor more efficient, comprising:
 providing an electric motor having a rotor being rotatable in a first direction relative to a stator winding, a first and a second transistor electrically connected to the stator winding and to a processor, the rotor having magnets of first and second polarities separated at polarity changing points;   a sensor sensing a first polarity changing point, the sensor sending a first triggering signal to the processor;   upon receipt of the first triggering signal, the processor delaying by a time period (t 1 ) before sending a first activation signal to the first transistor to start rotating the rotor in the first direction, the first activation signal lasting for a time period (l 1 );   the processor measuring a current A 1  driving the electric motor at a rotational speed;   the sensor sensing a second polarity changing point, the sensor sending a second triggering signal to the processor;   upon receipt of the second triggering signal, the processor delaying by a time period (t 1 ′) before sending a second activation signal to the second transistor to continue rotating the rotor in the first direction, the second activation signal lasting for a time period (l 2 );   the processor measuring a current A 2  driving the electric motor at the rotational speed;   the processor comparing the current A 1  to the current A 2  and selecting time period (t 1 ) for sending activation signals when the current A 2  is greater than the current A 1  and selecting time period (t 1 ′) for sending activation signals when the current A 1  is greater than the current A 2 ; and   the processor iteratively changing the time period (t 1 ) for each activation signal sent until a minimum current A min  is found by comparing measured currents to optimize an efficiency of the electric motor.   
     
     
         2 . The method according to  claim 1  wherein the method further comprises using a first PWM pulse as the first activation signal. 
     
     
         3 . The method according to  claim 1  wherein the method further comprises varying a length of the first PWM pulse to the first transistor. 
     
     
         4 . The method according to  claim 1  wherein the method further comprises measuring the current A 1  and the current A 2  at a constant rotational speed (ω) of the rotor. 
     
     
         5 . The method according to  claim 1  wherein the method further comprises the processor continuously monitoring currents driving the electric motor. 
     
     
         6 . The method according to  claim 1  wherein the method further comprises alternatingly using the first and second transistor to drive the rotor in the first rotational direction. 
     
     
         7 . A method for changing a rotational direction of a rotor of an electric motor, comprising:
 providing an electric motor having a rotor rotatable in a first direction and in a second opposite direction relative to a stator, a first and a second transistor electrically connected to the stator and to a processor, the rotor having magnets of first and second polarities separated at polarity changing points, a first magnetic sensor located (α 1 ) degrees prior to an activation point when the rotor rotates in the first rotational direction and a second magnetic sensor located (α 2 ) degrees prior to an activation point when the rotor rotates in the second opposite rotational direction;   the first magnetic sensor sensing a first change of polarity at a first polarity changing point on the rotor and sending a first triggering signal to the processor,   after receipt of the first triggering signal, the processor sending a first activation signal to the first transistor to keep on rotating the rotor in the first rotational direction;   the processor receiving a change of rotation command;   the processor sending a second activation signal to the second transistor before sending any activation signal to the first transistor to rotate the rotator in the second opposite rotational direction;   the second magnetic sensor sensing a second change of polarity at a second polarity changing point on the rotor and sending a second triggering signal to the processor; and   after receipt of the second triggering signal, the processor sending a third activation signal to the first transistor to keep on rotating the rotor in the second opposite rotational direction.   
     
     
         8 . The method according to  claim 7  wherein the method further comprises using a first voltage interval to characterize the first rotational direction and a second voltage interval to characterize the second rotational direction.