Suppliers of frequency converter supporting equipment remind you that with the arrival of the industrial era, the use of frequency converters is becoming increasingly popular. We need to ensure the selection and matching of frequency converters by first selecting the correct type based on the nature of the load. The general principle is to match the nature of the load characteristics with the characteristics of the frequency converter.
When selecting a frequency converter, the actual motor current value should be used as the basis for selecting the frequency converter, and the rated power of the motor can only be used as a reference. Secondly, it should be fully considered that the output of the frequency converter contains high-order harmonics, which can cause the power factor and efficiency of the motor to deteriorate.
Voltage matching: The rated voltage of the frequency converter matches the rated voltage of the motor.
Current matching: For ordinary centrifugal pumps, the rated current of the frequency converter matches the rated current of the motor. For special loads such as deep water pumps, it is necessary to refer to the motor performance parameters to determine the inverter current and overload capacity based on the maximum current. The current setting of the frequency converter should not be less than 1.1 times the rated current of the motor, and the maximum current is generally set to 1.5 times the rated current of the motor.
About One to Many
One to many refers to a frequency converter with multiple electric motors. The capacity of the frequency converter is the sum of the capacities of multiple motors (based on current), and it is best to amplify it by 10% to 15%. At the same time, it is necessary to ensure that each motor is loaded appropriately, with as much force as possible, neither running empty nor overloaded. Each motor should perform its own duties, cooperate with each other, and coexist peacefully; But if the control is not good, some loads are heavy, some loads are light, some are exhausted, and some are idle. As a result, the motor with heavy loads heats up and burns, and the entire system is paralyzed, which is not worth the loss. Therefore, be careful when delaying for a long time.
So, conversely, can we drag one more frequency converter with one electric motor? Answer: Absolutely prohibited!!!
About cables
If the frequency converter needs to operate with a long cable, measures should be taken to suppress the influence of the long cable on the ground coupling capacitance and avoid insufficient output of the frequency converter. Therefore, in this case, the capacity of the frequency converter should be increased by one level or an output reactor should be installed at the output end of the frequency converter. When a frequency converter is used to control several motors in parallel, it is necessary to consider that the total length of the cables from the frequency converter to the motors is within the allowable range of the frequency converter.
Regarding special application scenarios
1. If the ambient temperature is high, the switching frequency is high, and the altitude is high, it will cause the frequency converter to reduce its capacity, and the frequency converter needs to be amplified by one level for selection.
2. When using a frequency converter to drive a high-speed motor, due to the low reactance of the motor, the increase in high-order harmonics leads to an increase in the output current value. Therefore, the selection of frequency converters for high-speed motors should have a capacity slightly larger than that of ordinary motors.
3. When driving explosion-proof motors, the frequency converter does not have explosion-proof structures and should be placed outside of hazardous areas.
4. When choosing a frequency converter, it is important to pay attention to whether its protection level matches the situation on site.
other
1. When using a frequency converter to drive a wound rotor asynchronous motor, most of the existing motors are utilized. It is easy to cause overcurrent tripping due to ripple current, so a frequency converter with slightly larger capacity than usual should be selected.
2. For loads with large torque fluctuations such as compressors and vibration machines, as well as peak loads such as hydraulic pumps, it is necessary to understand the power frequency operation and choose a frequency converter with a rated output current greater than its maximum current.
3. When using a frequency converter to control a Roots blower, due to its high starting current, it is important to pay attention to whether the capacity of the frequency converter is large enough when selecting it.
4. When using a frequency converter to drive a gear reduction motor, the range of use is limited by the lubrication method of the rotating parts of the gear. Do not exceed the maximum allowable speed.
5. Single phase motors are not suitable for frequency converter drive.
The influence and measures of the distance between the frequency converter and the motor on the system
In industrial use sites, the distance between the frequency converter and the motor installation can be roughly divided into three situations: source long distance, medium distance, and short distance. Within 20m is considered close range, 20-100m is considered medium range, and above 100m is considered long range.
If the distance between the frequency converter and the motor is within 20m, it can be directly connected to the frequency converter;
For medium distance connections between frequency converters and motors ranging from 20m to 100m, it is necessary to adjust the carrier frequency of the frequency converter to reduce harmonics and interference; For long-distance connections of over 100m between frequency converters and motors, not only should the carrier frequency be moderately reduced, but also output AC reactors should be installed.