Correct selection of inverter is very important for the normal operation of the control system. When we choose an inverter, we must first understand the load characteristics driven by the inverter. Today, Dalan Motor manufacturers will introduce three common load types in production machinery.
1. Constant torque load
The load torque TL has nothing to do with the speed n, TL always remains constant or substantially constant at any speed. When the inverter drives a load of constant torque, the torque at low speed should be large enough and have sufficient overload capacity. If you need to run at a steady speed at low speed, you should consider the heat dissipation capacity of the standard asynchronous motor to avoid the motor's temperature rise being too high.
2. Constant power load
The torque required by the machine tool spindle and rolling mill, paper machine, coiler and uncoiler in the plastic film production line is generally inversely proportional to the speed, which is called a constant power load. If the range of the motor's constant torque and constant power speed regulation is consistent with the load's constant torque and constant power range, the so-called "matching" situation, the capacity of the motor and the capacity of the inverter are the smallest.
3. Loads of fans and pumps
When the air volume and flow required by various fans are reduced, the use of frequency converters to adjust the air volume and flow through speed regulation can greatly save electrical energy. Because the power required at high speed increases too fast with the speed of rotation, which is proportional to the cube of the speed, it should generally not allow fans and pumps to run over power frequency.
Four, matters needing attention when selecting the inverter
(1) When selecting the inverter, the actual motor current value should be used as the basis for selecting the inverter, and the rated power of the motor can only be used as a reference.
(2) If the inverter needs long cable operation, measures should be taken to suppress the influence of the long cable on the coupling capacitance of the ground to avoid insufficient output of the inverter.
(3) For some special applications, such as high ambient temperature, high switching frequency, high altitude, etc., it will cause the derating of the inverter, and the inverter needs to be enlarged by one gear to select.
(4) When selecting an inverter for high-speed inverter motors, it should be slightly larger than the inverter for ordinary motors.
(5) When using a frequency converter to drive a gear reduction motor, the range of use is restricted by the lubrication method of the gear rotating part. Therefore, do not exceed the maximum speed allowable value.
(6) When the inverter drives the wound rotor asynchronous motor, therefore, the overcurrent trip phenomenon caused by ripple current is easy to occur, so an inverter with a larger capacity than the normal one should be selected.
(7) When the frequency converter drives the synchronous frequency conversion motor, the output capacity will be reduced by 10% to 20% compared with the power frequency power supply. The continuous output current of the frequency converter is greater than the unit value of the synchronous motor rated current and the synchronous drawn current product.
(8) When selecting an inverter, it is necessary to pay attention to whether its protection level matches the situation on site. Otherwise, the dust and moisture on the site will affect the long-term operation of the inverter.
----- Responsible Editor: Dalan Oil Pump Motor 02-Procurement Consultant
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