The solution to the influence of Mitsubishi inverter on the motor

Generally, asynchronous motors are planned according to constant frequency and constant voltage, and it is impossible to completely adapt to the requirements of frequency conversion speed regulation. The following is the influence of the inverter on the motor:

The solution to the influence of Mitsubishi inverter on the motor

The solution to the influence of Mitsubishi inverter on the motor

Regardless of the form of inverter, different degrees of harmonic voltage and current occur in the operation of the building automation training device, so that the motor runs under non-sinusoidal voltage and current. According to the introduction of the data, taking the sine wave PWM inverter commonly used as an example, its low harmonic is basically zero, and the weight of the remaining high harmonic is about twice as large as the carrier frequency: 2u 1 (u is the modulation ratio).

PWM, or Pulse Width Modulation, is a manipulation skill that uses the digital output of a microprocessor to manipulate analog circuits. PWM is widely used in many fields, from measurement and communication to power control and changeover, due to its advantages of simple operation, sensitivity, high power and good dynamic response. PWM is the term used in switched-mode regulated power supplies. This is classified according to the control method of voltage stabilization, and in addition to the PWM nursing person model, there are PFM type and PWM and PFM hybrid type. PWM manipulators are found in many of today's miniature manipulators.

Higher harmonics will cause the addition of stator copper loss, rotor copper (aluminum) consumption, iron consumption and additional loss of the motor of the building automation training device, the most obvious is the rotor copper (aluminum) consumption. Since it rotates at a synchronous speed close to the fundamental frequency, a large rotor loss occurs when the higher harmonic voltage cuts the rotor guide bar with a large slip. In addition to this, additional copper loss due to the skin effect needs to be taken into account. These losses will make the motor rated heat, power decrease, output power decrease, such as the general three-phase asynchronous motor running in the non-sinusoidal condition of the inverter output, its temperature rise generally to add 10%-20% The power supply is a device that supplies power to electronic equipment, also known as a power supply, which supplies the electric energy required by all components in the computer.

At present, many small and medium-sized inverters use PWM control methods. His carrier frequency is about several thousand to more than ten thousand kHz, which makes the stator winding of the motor to withstand a high voltage rise rate, which is equivalent to applying a steep impulse voltage to the motor, so that the inter-turn insulation of the motor can withstand harsh detection. In addition, the rectangular chopping impulse voltage generated by the PWM inverter is superimposed on the motor operating voltage, which will pose a threat to the ground insulation of the motor, and the ground insulation will accelerate the aging under the repeated impact of high voltage.

Generally, when the inverter is used for power supply of asynchronous motors, the vibration and noise caused by electromagnetic, mechanical, ventilation and other elements will become more complicated. The harmonics contained in the variable frequency power supply at each time interfere with the inherent space harmonics of the electromagnetic part of the motor to form various electromagnetic excitation forces. When the frequency of the electromagnetic force wave is the same or close to the natural vibration frequency of the motor body, the resonance phenomenon will occur, and then the noise will be increased. Because the working frequency range of the nursing model motor is wide and the speed change range is large, it is difficult for the frequency of various electromagnetic force waves to avoid the natural vibration frequency of each component of the motor.

Because after the inverter is selected for power supply, the motor can be started at a very low frequency and voltage with no impulse current, and various braking methods provided by the inverter can be used for rapid braking, which creates conditions for the completion of frequent starting and braking, so the mechanical system and electromagnetic system of the motor are under the action of cyclic alternating force, which brings fatigue and accelerated aging problems to the mechanical structure and insulation structure.

First of all, the impedance of the asynchronous motor is not ideal, and when the frequency is low, the loss caused by the higher harmonics in the power supply is larger. Secondly, when the speed of the general asynchronous motor decreases, the proportion of the cooling air volume and the cubic speed decreases, resulting in the deterioration of the low-speed cooling of the motor, the rapid increase of temperature rise, and the constant torque output of the nursing model is difficult to complete.

The solution to the influence of Mitsubishi inverter on the motor

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