How to distinguish between ordinary motors and variable frequency motors?

Update:10 Nov 2020

1. The difference in structure between ordinary motor and variable frequency motor

01. Higher insulation requirements
  The insulation class of general frequency conversion motors is F or higher, strengthen the insulation to the ground and the insulation strength of the turns, especially considering the ability of the insulation to withstand impulse voltage.

02. The vibration and noise requirements of variable frequency motors are higher
   Inverter motors must fully consider the rigidity of the motor components and the overall (public number: pump housekeeper), and try to increase its natural frequency to avoid resonance with various force waves.

03. Different cooling methods for variable frequency motors
  The frequency conversion motor generally adopts forced ventilation cooling, that is, the main motor cooling fan is driven by an independent motor.

04. Different protection measures
   Bearing insulation measures should be adopted for variable frequency motors with a capacity exceeding 160KW. The main reason is that the asymmetry of the magnetic circuit is easy to occur, and the shaft current is also generated. When the currents generated by other high frequency components work together, the shaft current will greatly increase, which will cause damage to the bearing. Therefore, insulation measures are generally taken. For constant power variable frequency motors, when the speed exceeds 3000/min, special high-temperature-resistant grease should be used to compensate for the temperature rise of the bearing.

05. Different cooling systems
  The frequency conversion motor cooling fan uses an independent power supply to ensure continuous heat dissipation.

2. The difference in the design of ordinary motors and variable frequency motors
01. Electromagnetic design
   For ordinary asynchronous motors, the main performance parameters considered when redesigning are overload capacity, starting performance, efficiency and power factor. As for the variable frequency motor, since the critical slip is inversely proportional to the power frequency, it can be started directly when the critical slip is close to 1. Therefore, overload capacity and starting performance do not need to be considered too much, but the key issue to be solved is how to improve the motor Adaptability of non-sine wave power supply.

02. Structural design
  In the structural design, it is also necessary to consider the influence of the non-sinusoidal power supply characteristics on the insulation structure, vibration, and noise cooling methods of the inverter motor.

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