One stroke to distinguish between variable frequency motor and ordinary motor

Introduction: Xiao Bian as an outsider after reading the following content finally understand what is the frequency conversion machine, the summer is finally not fainted. Shaoyou below we have a trick to distinguish between variable frequency motor and ordinary motor.

Inverter motor - used for motors with special frequency converters. Its difference from ordinary motors lies in the addition of strong cooling fans. The power of the fan comes from a separate power source and cannot be discharged from the main motor. The role of the forced cooling fan is to ensure the cooling of the motor at low speeds.

Variable frequency motor can make the motor speed can be adjusted, and then according to the load situation to achieve the purpose of energy saving. The ordinary motor is a device with a fixed speed and cannot be adjusted. There is no major difference, but its coil distribution capacitance is smaller, the resistance of the silicon steel sheet is larger, so that the high-frequency pulse has a small impact on the motor, and the motor inductance filter effect is better.

The manufacturing process of ordinary motors and variable frequency motors varies greatly. The common motor, that is, the industrial frequency motor, only needs to consider the starting process and the working condition of one point of the power frequency, and then design the motor; while the variable frequency motor needs to consider the starting process and all the working conditions in the frequency conversion range, and then design the motor.

The difference also has the following points:

1, from the point of view of the frequency, the frequency conversion motor is a bad motor, ordinary motor is a good motor;

2. As the PWM output of the inverter modulates and oscillates the sinusoidal alternating current, it contains a large number of harmonics. Generally, it needs to be filtered by the reactor before it can enter the ordinary motor, otherwise the ordinary motor will generate heat;

3. In order to adapt to the PWM output of the inverter, the PWM sinusoidal alternating current contains a large number of harmonics. Specially-made frequency conversion motor. Its role can actually be understood as reactor plus ordinary motor;

4, that is to say, the same power inverter motor than ordinary motor core cross-section larger. The number of turns of the coil must be large; the insulation must be high, and the special cooling fan motor must be used.

5, in order to adapt to the needs of weak magnetic speed control, taking into account the bearing capacity and high-speed rotor dynamic balance;

6, this variable frequency motor does not have better torque characteristics, but to overcome the general motor does not adapt to PWM modulation and wide-wave simulation of sinusoidal alternating current needs;

7, if the frequency conversion motor does not have the above characteristics and requirements, it is false frequency conversion motor frequency conversion.

Compared with ordinary motors and constant frequency constant voltage, the difference in structure is:

1. Insulation grade: Generally F class or higher, strengthen the insulation of the ground insulation and wire insulation, in particular the ability to withstand impact voltage insulation.

2. Vibration and noise problems of the motor: Take full account of the rigidity of the motor components and the entire body, and try to increase the natural frequency so as to avoid resonance with each secondary wave.

3. Cooling method: Forced-ventilation cooling is generally adopted, that is, the main motor cooling fan is driven by an independent motor.

4. To prevent shaft current measures, bearing insulation measures shall be used for motors with capacity exceeding 160KW. Mainly is easy to produce magnetic circuit asymmetry, it will also produce the shaft current. When the current generated by other high-frequency components combine to act together, the shaft current will greatly increase, which will lead to bearing damage. Therefore, insulation measures are generally adopted.

5. For constant-power variable-frequency motors: When the speed exceeds 3000/min, a special high-temperature-resistant grease should be used to compensate for the temperature rise of the bearing.

What are the disadvantages of common low-frequency motor running for a long time?

1. It is a resonance problem at a certain frequency; 2. It is a problem of heat dissipation. When the power frequency is lower than the bottom, the higher harmonics in the power supply cause a greater loss. In addition, her own fan is not enough to cool itself at low frequencies. Life expectancy has plummeted.

Supplement: The motor speed regulation can also be performed through the fluid coupling. Hydraulic coupler is a mechanical device that uses liquid medium to transfer rotational speed. The active input shaft end is connected with the original conveyor, and the output output shaft end is connected with the load shaft end. By adjusting the pressure of the liquid medium, the output shaft is The speed is changed.

Ideally, when the pressure tends to infinity, the output speed is equal to the input speed, which is equivalent to a steel coupling. When the pressure is reduced, the output speed is reduced accordingly, the medium pressure is continuously changed, and the output speed can be adjusted steplessly below the input speed.

However, the hydraulic coupler is worse than the variable frequency motor in the range of speed control, speed control accuracy, and efficiency, but the price is relatively cheap. 3. Normal motors do not allow long-term low-frequency work, otherwise serious heat may burn out.