From: APEC Project: EWG 04 2019S
Normal motors are designed according to constant frequency and constant voltage, which cannot fully meet the requirements for inverter speed control. Therefore, it cannot be used as an inverter motor.
1. The impact of the inverter on the motor is mainly in the efficiency and temperature of the motor.
The inverter generates different degrees of harmonic voltage and current during operation, so the motor operation under non-sinusoidal voltage and current. The high-order harmonics within will increase the copper loss of stator, copper loss of rotor, iron loss, and additional loss of the motor. The most significant is the copper loss of rotor, these losses will make the motor hoter, reduce the efficiency, and reduce the output power. The temperature increase of normal motors generally increases by 10%-20%.
2. The insulation ability of the motor
The carrier frequency of the inverter is from several kHz to more than a dozen kHz. The motor windings must afford high rate voltage rise, which is equivalent to imposing a steep impulse voltage on the motor, so that the inter-turn insulation of the motor is in serious condition.
3. Harmonic electromagnetic noise and vibration
When a regular motor is powered by a frequency converter, it will make the vibrations and noise caused by electromagnetic, mechanical, ventilation and other factors more complex. The harmonics inside the inverter interfere with the spatial harmonics inherent in the electromagnetic part of the motor to form various electromagnetic excitation forces, thus increasing the noise. Due to the wide range of the operation frequency of the motor and the wide range of rotation speed, the frequency of various electromagnetic force waves is difficult to avoid the natural vibration frequency from various structural parts of the motor.
4. Cooling issue at low speed
When the power frequency is low, the loss caused by the higher harmonics in the power supply is larger. Secondly, when the motor speed decreases, the air-flow of cooling will decreases with proportional to the cube of the speed. The heat of the motor cannot be dissipated, and the temperature rise sharply increases, making it difficult to achieve constant torque output.
1. Higher insulation requirements
Generally, the insulation class of the inverter duty motor is F or higher, strengthen the insulation to the ground and the insulation strength of the turns, and especially consider the ability of the insulation to withstand impulse voltage.
2. The vibration and noise requirements of inverter duty motors are higher
The invert duty motor should fully consider the rigidity of the motor components and the whole motor, and try to increase its natural frequency to avoid resonance caused by the secondary force wave.
3. Inverter duty motor cooling method is different
The inverter duty motors generally use forced air cooled, that is, the main motor cooling fan is driven by an independent motor.
4. Different protection measures are required (according to customer requirements, if the customer's equipment is used in a harsher environment, when there is such a special demand, the assembly will particularly select bearings with higher temperature resistance)
Bearing insulation measures should be adopted for inverter motors with a capacity exceeding 160KW. Mainly it is easy to produce asymmetry of the magnetic circuit, and also produce shaft current. When the currents generated by other high-frequency components work together, the shaft current will greatly increase, resulting in damage to the bearing, so generally insulation measures must be taken. For constant power inverter motors, when the speed exceeds 3000/min, a special high temperature lubricating grease must be used to compensate for the increase in the bearing temperature.
5. Different cooling system
The inverter duty motor cooling fan uses an independent power supply to ensure continuous heat dissipation.
- High Dynamical Response
- Class H insulation
- Small size and space saving
- Independent cooling fan
- High rigidity red cross alloy steel shaft
- Can be customized according to customer requirements.
- Maximum and rated torque excellent outpu and precision control of medium and low speed.
- With inverter and driver, can run the command accurately.
- Not requiring maintenance(The position of magnet poles are unnecessary to be detected for driven because the direction of magnet flux is determined by the voltage. And there are not electors ,brushes,magnets)
- Perfect protection accessories(Thermal Protector(NC)+ Thermistor)
