The Reason and Solution of Air Compressor's Frequency Conversion Retrofitting Burning Motor

First, the reasons for the conversion of conventional air compressor frequency conversion burning motor:

At present, many small and medium frequency converters adopt the PWM control method. His carrier frequency is about several thousand to ten kilohertz, which makes the stator winding of the motor withstand a very high rate of voltage rise, which is equivalent to applying a steep steep voltage to the motor, so that the inter-turn insulation of the motor is more tolerated. The harsh test. At the same time, regardless of the type of inverter, harmonic voltage and current are generated in different degrees during operation, so that the motor operates under non-sinusoidal voltage and current. Rejection data introduction, with the current commonly used sine wave PWM inverter as an example, its low harmonic is basically zero, and the rest of the higher harmonic component is about 2 times larger than the carrier frequency: 2u+1 (u For modulation ratio). Higher harmonics can cause increased stator copper losses, rotor copper (aluminum) losses, and iron losses, as well as additional losses. The most notable is rotor copper (aluminum) consumption. Since the asynchronous motor rotates at a synchronous speed that is close to the fundamental frequency, a large rotor loss occurs after the higher harmonic voltage cuts the rotor bar with a large slip. In addition, additional copper consumption due to skin effect needs to be considered. These losses will cause the motor to generate heat, reduce the efficiency, and reduce the output power. For example, if an ordinary three-phase asynchronous motor is operated under the non-sinusoidal power supply output of the inverter, the temperature rise generally increases by 10%-20%. In summary, it is very easy to burn the motor.

Second, the air compressor frequency conversion energy-saving method:

The current status of screw compressors used in the screw air compressor industry, the current market is still generally used in the direct drive of the power grid, air compressors rely mainly on the degree of valve closing of the intake valve to achieve air volume adjustment, even if the gas consumption is very low In the absence of air, the motor is still running at full speed and energy is wasted. Since an ordinary three-phase asynchronous variable-frequency motor is designed based on the rated point, when the motor speed decreases, it will cause a sharp drop in the motor power factor and efficiency. Therefore, it is not the optimal matching motor for the inverter-type air compressor motor.

The advantages of permanent magnet synchronous motor In recent years, with the rapid development of power electronics technology, new motor control theory and rare earth permanent magnet materials, Shanghai Huihang Energy Saving Equipment Co., Ltd. has promoted and applied permanent magnet synchronous motors to air compressors. Today, energy conservation and environmental protection are increasingly valued, and have been widely used in many industries.

The advantages of permanent magnet synchronous motor and ordinary asynchronous variable frequency motor are:

1. Efficiency High Efficiency High refers to the efficiency of the rated power point is the average efficiency in the entire speed range. The permanent magnet synchronous motor increases the contact loss between the carbon brush and the slip ring, including the electrical loss and mechanical loss of the contact portion.

2. Small starting current and large starting torque According to the V/F characteristics of the inverter, in the low frequency starting, the main magnetic field in the asynchronous variable frequency speed regulating motor is low, the power factor is low, the starting current is large, and the starting torque is very small; The main magnetic field of the rare earth permanent magnet synchronous frequency conversion motor is constant, the stator current is almost all active current, the starting current is small, and the starting torque is large.

3, force energy index good motor power index refers to the product of motor efficiency and power factor, on behalf of the motor power indicators. The efficiency and power factor of the rare earth permanent magnet variable frequency motor approximates a horizontal curve, further improving the efficiency of the use of electrical energy and the quality factor of the power grid.

4. Small size and light weight Due to the use of high-performance permanent magnetic materials to provide magnetic fields, the air gap magnetic field of permanent magnet motors is greatly enhanced compared to induction motors. The size and weight of permanent magnet motors can be greatly reduced compared to induction motors. Permanent magnet motor is only 92kg, equivalent to 45.8% of the weight of the asynchronous motor.

Based on the above comparative advantages, at present, the permanent magnet motor is the best choice for frequency conversion screw air compressor drive motor, it is more efficient and energy-saving than ordinary three-phase asynchronous variable frequency motor!

Therefore, in order to make frequency conversion energy-saving reforms on ordinary air compressors, air compressors must be equipped with permanent magnet motors. Therefore, Shanghai Huihang Energy-saving and Environmental Protection Equipment Co., Ltd. developed a permanent magnet frequency conversion air compressor, which was continuously developed by the company. The two-stage compression technology in the centrifuge is applied to the permanent magnet frequency conversion air compressor, which makes the energy saving and air compressor of the emblem energy saving brand more energy-saving and more stable.