11 differences between inverter motors and ordinary motors!

Variable frequency motor - used in special occasions with frequency converters, it differs from ordinary motors in that it adds a strong cooling fan. And the power of this fan comes from a separate power source and cannot be connected from the main motor. The function of a strong cooling fan is to ensure the cooling of the motor at low speeds.

Variable frequency motors can adjust the speed of the motor, thereby achieving energy-saving goals based on load conditions. A regular motor is a device with a fixed speed and cannot be adjusted.

There is no major difference, but its coil distribution capacitance is smaller, and the resistance of the silicon steel sheet is higher. This reduces the impact of high-frequency pulses on the motor, and the inductance filtering effect of the motor is better.

The manufacturing process of ordinary motors and variable frequency motors varies greatly. Ordinary motors, also known as power frequency motors, only need to consider the starting process and the working conditions at one point of the power frequency, and then design the motor; The variable frequency motor needs to consider the starting process and the working conditions of all points within the variable frequency range, and then design the motor.

There are also the following differences:

1. From the perspective of power frequency, variable frequency motors are inferior, while ordinary motors are good motors

2. Due to the PWM width modulation wave output by the frequency converter simulating sinusoidal alternating current, which contains a large amount of harmonics, it usually needs to be filtered by a reactor before entering a regular motor, otherwise the regular motor will generate heat;

3. In order to adapt to the PWM width modulation wave output by the frequency converter, the simulated sinusoidal alternating current contains a large amount of harmonics. Specially produced variable frequency motor. Its function can actually be understood as a reactor plus an ordinary motor;

4. That is to say, variable frequency motors of the same power have a larger iron core cross-section than ordinary motors. The coil turns should be multiple and the wire diameter should be large; High insulation, specialized cooling fan motor;

5. In order to meet the needs of weak magnetic speed regulation, the bearing capacity and high-speed rotor dynamic balance have been considered;

6. This type of variable frequency motor does not have better torque characteristics, but only overcomes the need for ordinary motors not to adapt to PWM width modulation wave simulation of sinusoidal alternating current;

7. If the variable frequency motor does not meet the above characteristics and requirements, it is a fake variable frequency motor.

Motors are more common than ordinary motors

The difference in structure between constant frequency and constant voltage is:

1. Insulation level: Generally F level or higher, strengthen the strength of ground insulation and wire turn insulation, especially considering the ability of insulation to withstand impulse voltage.

2. Regarding the vibration and noise issues of the motor: It is necessary to fully consider the rigidity of the motor components and the overall structure, and strive to increase its natural frequency to avoid resonance with various force waves.

3. Cooling method: Generally, forced ventilation cooling is used, that is, the main motor cooling fan is driven by an independent motor.

4. Measures to prevent shaft current: For motors with a capacity exceeding 160KW, bearing insulation measures should be taken. The main reason is that it is prone to magnetic circuit asymmetry and also generates shaft current. When the currents generated by other high-frequency components combine, the shaft current will greatly increase, leading to bearing damage. Therefore, insulation measures are generally taken.

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

What are the drawbacks of regular motors operating at low frequencies for a long time

1. It is a resonance problem at a certain frequency;

2. It is a heat dissipation problem. When the power frequency is low, the losses caused by higher harmonics in the power supply are relatively large. In addition, at low frequencies, the fan she comes with is not enough to cool herself, resulting in a sudden decrease in the lifespan of the motor.

Supplement: In addition, motor speed regulation can also be achieved through hydraulic couplers. Hydraulic coupling is a mechanical device that utilizes liquid medium to transmit speed. Its active input shaft end is connected to the original transmission machine, and the driven output shaft end is connected to the load shaft end. By adjusting the pressure of the liquid medium, the speed of the output shaft can be changed. In an ideal state, when the pressure approaches infinity, the output speed is equal to the input speed, equivalent to a rigid coupling. When the pressure decreases, the output speed decreases accordingly. By continuously changing the medium pressure, the output speed can be infinitely adjusted below the input speed.

However, the hydraulic coupling is inferior to variable frequency motors in terms of speed range, speed accuracy, efficiency, and other aspects, but the price is relatively cheap.

3. Ordinary motors are not allowed to work at low frequencies for long periods of time, otherwise severe heating may cause burnout.