General motor frequency conversion motor are planned according to the constant frequency and constant pressure, can't be completely used to frequency converter speed control requirements, and can't do more USES frequency conversion motor. 1, the influence of the frequency converter for motor is mainly in the power and temperature of the motor frequency converter can occur in the operation of different degree of harmonic voltage and current, make the motor in non-sinusoidal voltage, power flow operation, and high order harmonic can cause motor stator copper loss, iron loss and copper loss, rotor add additional loss, the most significant is the rotor copper loss, the loss will make motor fever, additional power decrease, output power decreases, and the general motor temperature rise to add 10% to 20%. 2, motor insulation strength problem from several thousand to more than 10 KHZ inverter carrier frequency, make the motor stator winding to accept high voltage build-up rate, equivalent to impose great impulse voltage gradient on motor, make the turn-to-turn insulation of the motor to accept more severe test. 3, harmonic electromagnetic noise and sensation general motor when choosing the inverter power supply, can make the electromagnetic, mechanical, ventilation caused by such factors as sensation and noise have become increasingly cluttered. Variable frequency power supply is contained in every harmonic and motor electromagnetic part inherent space harmonic do to each other, and constitute a variety of electromagnetic exciting force, and then increase the noise. Because the motor operating frequency scale, wide speed change big, all kinds of the electromagnetic wave frequency is difficult to avoid the structural natural oscillation frequency of motor. 4, when low speed cooling problems when power frequency is low, the power loss caused by higher harmonic in the larger; Second alternative motor speed falls, cooling air volume and three direct ratio decreases, and the rotational speed of the motor of heat do not go out, temperature rise sharply to add, it is difficult to realize the constant torque output. General motors and the difference of variable frequency motor 1. Insulation class generally higher frequency conversion motor insulation class is F or higher, strengthen the insulation and line turn insulation strength, especially want to consider the ability of impact resistance voltage insulation. 2. The oscillation frequency conversion motor, noise components requiring higher frequency conversion motor, we must give full consideration to the motor and overall rigidity, trying our best to advance its natural frequency, in order to avoid resonance occur with all the force wave. 3. Frequency conversion motor cooling method forced ventilation cooling is generally selected different frequency conversion motor, the main motor cooling fan with independent motor drive. 4. Protection to different requirements for capacity beyond 160 kw variable frequency motor should choose bearing insulation measures. Mainly prone to asymmetric magnetic circuit, can also occur shaft current, when combined with other high frequency weight of current role, together will greatly add shaft current, and then result in bearing damage, so generally take insulation measures. The constant power variable frequency motor, when the speed beyond 3000 / min, should choose a special grease, high temperature resistant to compensate for the temperature of the bearing. 5. Different frequency conversion motor cooling fan cooling system choose independent power supply, ensure that continue to heat dissipation ability.
