Dc brushless pump not all sine wave can solve the noise problem

Most people think that as long as it is the use of sine wave controller to control the silent pump, the sound will reach the level of super quiet, DC pump using sine wave, compared with the ordinary pump noise will be smaller, and the main difference between ordinary DC submersible pump, or in the use of sine wave controller, plus sine wave controller, the noise will be correspondingly smaller. But to achieve the ultimate quiet sine wave frequency conversion technology is not a space of my circuit scheme can solve. Because the structure of the pump body is different, coupled with the level of programming and circuit design engineers are different, the mute pump control scheme is very far related.

Sinusoidal DC mute water pump for the existing motor rotor is straight pole, rotor steel plate without holes, rotor at both ends of the plate, is no metal cage structure, there is a stator tooth and stator armature reaction, the air gap magnetic field distortion, the output voltage waveform distortion. In this paper, a sinusoidal motor rotor with simple structure is proposed to make the output voltage waveform of the generator meet the requirements of the actual sinusoidal wave.

Sine wave controller is the main command device that changes the wiring of the control circuit of the main circuit and changes the resistance value in the circuit to control the start, speed regulation, braking and reverse of the motor in a predetermined order. It is composed of program counter, instruction register, instruction decoder, time sequence generator and operation controller. It is the "decision mechanism" of issuing orders, that is, to complete the coordination and command of the operation of the whole computer system.

The traditional brushless DC motor adopts square wave control mode, which is simple to control and easy to realize. At the same time, there are some problems such as torque ripple and commutation noise, and there are limitations in some application fields that require noise. For these applications, sine wave control can solve this problem well.

Sinusoidal wave control of brushless DC motor means that sinusoidal current is generated in the windings by applying a certain voltage to the motor windings, and the purpose of controlling the motor torque is achieved by controlling the amplitude and phase of sinusoidal current. Compared with the traditional square wave control, the phase current of the motor is sinusoidal and continuously changes without phase commutation current mutation, so the motor operation noise is low.

(1) Simple sine wave control: a certain voltage is applied to the motor windings, so that the voltage phase voltage is sine wave. Since the motor windings are inductive load, the motor phase current is also sine wave. By controlling the amplitude and phase of the motor phase voltage to control the phase and amplitude of the current, voltage loop control, the realization is relatively simple.

(2) Complex sinusoidal control: simple sinusoidal control is different. The goal of complex sinusoidal control is the phase current of the motor. A current loop is established to control the motor by directly controlling the phase and amplitude of the phase current. As the phase current of the motor is the orthodox signal, the current decoupling operation needs to be carried out, which is relatively complicated. The common ones are magnetic field oriented control (FOC) and direct torque control (DTC).

Simple sine wave control is to control the motor current by controlling the amplitude and phase of the motor sine phase voltage. Sinusoidal phase voltage is usually generated at both ends of the winding by applying a certain voltage to the end line of the motor. The common generation modes are sinusoidal PWM and space vector PWM. Because sinusoidal PWM principle is simple and easy to implement, it is usually used as PWM generation mode in simple and easy sine wave control.

Three-phase SPWM is the most common sinusoidal PWM generation mode, that is, to apply a sinusoidal voltage signal with a phase difference of 120 degrees to the three terminal lines of the motor. Because the neutral point is 0, the motor phase voltage is also sinusoidal, and the phase is the same as the applied sinusoidal voltage. Different from the common SPWM, the voltage Ua, Ub and Uc applied to the end line of the motor is not sine wave voltage when the minimum sine PWM of switching loss is adopted. At this time, the voltage of the center point of the motor is not 0, but the motor phase electricity is still sine. So this kind of control mode is line voltage control.

The calculation of rotational speed depends on the Hall sensor. In ideal condition, the interval between two adjacent Hall states is 60°. In practical application, due to the installation error, the actual interval is not 60°, which will introduce the calculation error. Different from square wave control, the Angle in sine wave control is continuously changing, while the three Hall sensors commonly used in BLDC can only provide six Angle information, namely 0°, 60°, 120°, 180°, 240°, 300°, and other Angle information cannot be obtained directly. The average velocity method is usually adopted, and the motor speed is assumed to be stable within a certain period of time. Other Angle information can be obtained by interpolating the Angle and velocity information of the previous Hall commutation.

Before the brushless DC pump starts, the rotor is in a static state, and only Hall sensor can be used to obtain the Angle information required by the sine control of the absolute position of the motor. Therefore, at the start stage of the motor, it is not possible to directly enter the sinusoidal control mode, so the square wave control mode is used to start the motor. When the motor is started and reliable reversing information is obtained, it can be cut into the sine wave control. In order to prevent large speed fluctuations, it is necessary to pay attention to the phase and amplitude balance transition of the current before and after switching.

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