Frequency converter selection considerations - Solutions - Huaqiang Electronic Network

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(1) Select the inverter according to the load characteristics. If the load is a constant torque load, select the siemens MMV/MDV inverter. If the load is a fan or a pump type, select the siemens ECO inverter.
(2) When selecting the inverter, the actual motor current value should be used as the basis for the inverter selection. The rated power of the motor can only be used as a reference. In addition, it should be fully considered that the output of the inverter contains higher harmonics, which will cause the power factor and efficiency of the motor to deteriorate. Therefore, compared with the power frequency grid power supply, the motor current is increased by 10% and the temperature rise is increased by about 20%. Therefore, when selecting the motor and the inverter, the situation should be taken into consideration, and a margin should be left to prevent the temperature rise from being too high and affect the service life of the motor.
(3) If the inverter is to be operated with a long cable, measures should be taken to suppress the influence of the long cable to the ground coupling capacitor to avoid insufficient output of the inverter. Therefore, the inverter should be amplified by one gear or installed with an output reactor at the output of the inverter.
(4) When the inverter is used to control several motors in parallel, it is necessary to consider the total length of the cable from the inverter to the motor within the allowable range of the inverter. If the specified value is exceeded, enlarge the first or second gear to select the inverter. In addition, in this case, the control mode of the inverter can only be V/F control mode, and the inverter cannot protect the overcurrent and overload protection of the motor. In this case, a fuse is added to each motor to achieve protection.
(5) For some special applications, such as high ambient temperature, high switching frequency, high altitude, etc., this will cause the inverter to derate, and the inverter needs to be amplified by one gear.
(6) When using a frequency converter to control a high-speed motor, the high-order motor also has a small reactance, and the high-order harmonic also increases the output current value. Therefore, when selecting a frequency converter for a high speed motor, it should be slightly larger than the inverter of a normal motor.
(7) When the inverter is used in a pole-changing motor, the capacity of the inverter should be fully selected so that the maximum rated current is below the rated output current of the inverter. In addition, when performing the pole number conversion during operation, the motor should be stopped first, otherwise the motor will be idling, which will cause damage to the inverter.
(8) When the explosion-proof motor is driven, the inverter does not have an explosion-proof structure, and the inverter should be placed outside the hazardous area.
(9) When using a frequency converter to drive a geared motor, the range of use is limited by the lubrication method of the rotating part of the gear. When the lubricating oil is lubricated, there is no limit in the low speed range; in the high speed range exceeding the rated speed, there is a danger that the lubricating oil will be used. Therefore, do not exceed the maximum speed tolerance.
(10) When the inverter drives the wound rotor asynchronous motor, most of the existing motors are used.
The winding motor has a lower impedance of the winding motor winding than a conventional squirrel cage motor. Therefore, an overcurrent trip due to ripple current is prone to occur, so select a converter that is slightly larger than the normal capacity. Generally, the winding motor is mostly used in the case where the flywheel torque GD2 is large, and more attention should be paid when setting the acceleration/deceleration time.
(11) When the inverter drives the synchronous motor, the output capacity is reduced by 10% to 20% compared with the commercial frequency power supply. The continuous output current of the inverter is greater than the product of the rated current of the synchronous motor and the value of the synchronous pull-in current.
(12) In the case of a load with a large torque ripple such as a compressor or a vibrating machine and a peak load such as a hydraulic pump, if the inverter is selected according to the rated current or power value of the motor, overcurrent may occur due to the peak current. Protect the action phenomenon. Therefore, you should understand the power frequency operation and select the inverter with a rated output current greater than its maximum current. When the inverter drives the submersible pump motor, because the rated current of the submersible pump motor is larger than the rated current of the normal motor, when the inverter is selected, its rated current is greater than the rated current of the submersible pump motor.
(13) When the inverter controls the Roots blower, since the starting current is very large, it is necessary to pay attention to whether the capacity of the inverter is large enough when selecting the inverter.
(14) When selecting a frequency converter, be sure to check whether its protection level matches the situation on site. Otherwise, dust and water vapor on the site will affect the long-term operation of the inverter.
(15) Single-phase motors are not suitable for inverter drive.