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.

Description

PRIOR APPLICATIONS[0001]This is a continuation-in-part application of U.S. patent application Ser. No. 13 / 974,089, filed 23 Aug. 2013.TECHNICAL FIELD[0002]The present invention pertains to a method for making a motor quieter such as a brushless direct current motor.BACKGROUND AND SUMMARY OF INVENTION[0003]Brushless fans are utilized in, for instance, computers, desktop fans, bathroom fans, and ventilation fans, and the like, because they are not as noisy as those operated by brushes. Nevertheless, brushless fan motors when operated, and when the stator energized electro-magnetic coils change polarization, an unwanted clicking or snapping noise can be heard particularly when the revolving fan blades do not override the clicking noise made by the fan motor. It is sometimes important that ventilation fans are as quiet as possible and the clicking noise should therefore be suppressed to avoid the noise problem.[0004]A brushless fan motor can be driven by direct current (DC) by feeding D...

AI Technical Summary

Benefits of technology

The patent describes a method to make a motor quieter by using a special type of signal called a pulse width modulated signal. This signal is sent to two transistors that control the current in a stator winding. The first transistor conducts the current, but the second tranistor is switched to instead of the first transistor to induce transients in the stator winding. This is suppressed by a capacitor, which has to be a specific type of capacitor that can handle high voltages. The use of a zener diode helps to set a limit on the voltage of the capacitor. Overall, this method makes the motor quieter by reducing the noise caused by the current spikes.

Problems solved by technology

Nevertheless, brushless fan motors when operated, and when the stator energized electro-magnetic coils change polarization, an unwanted clicking or snapping noise can be heard particularly when the revolving fan blades do not override the clicking noise made by the fan motor.

When the rpm of the motor is only controlled by the variation of the voltage, the motor becomes weak when operating at a low rpm.

Rapid openings of the transistors, i.e. when the PWM pulses are not truncated, results in the sudden flow of current through the stator windings, which creates the undesirable clicking noise in the stator windings of the coils.

If only the coil inductance is used to limit the increase of the current, then the current rushes into the coils too fast and causes the undesirable clicking noise in the stator windings.

The sensor thus determines how fast the motor rotates but it does not necessarily determine at what rpm the motor should rotate.

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