Disadvantages of variable frequency starting:
1, the cost is high, the price is much more expensive than the computer protection;
2, since almost all of the inverter by using PWM control, pulse modulation in the form of harmonic current in the inverter operation when the power supply side, and cause the voltage waveform distortion, power system harmonic interference, it will affect the efficiency of the system, the safe operation of heavy equipment damage and harm of power system;
3, overload makes the inverter beat relatively frequently, usually caused by the overload phenomenon, General Motors due to overload ability, as long as the parameters of the motor inverter parameter table is set up properly, generally do not appear motor overload. The inverter itself due to overload less easily overload alarm.
Soft start pump: connected in series between the power supply and the controlled motor, trigger the conduction angle of the AC voltage through the thyristor microcomputer control inside the tube, the motor input voltage from zero to a preset function increased gradually, until the end of starting, the motor is given full voltage soft starter, soft starter in the process the motor starting torque, speed increases gradually, increase gradually, until the thyristor wholeconduction motor working in the mechanical properties of rated voltage, to achieve a smooth start, reduce the starting current. Avoid starting overcurrent trip. When the motor reaches the rated speed, the starting process is finished, and the rated voltage is provided for the normal operation of the motor.
Shortcoming:
1, can not adjust the power frequency, so it can not start from zero voltage zero frequency motor, can not achieve zero impact start;
2, can not speed;
3. The soft starter exits the system after starting the motor and loses the protection function.
