Why can't the frequency of the inverter be adjusted?
1. Acceleration time is too short
In theory, the longer the acceleration time, the stronger the load-bearing capacity. If the acceleration time is set too short, the inverter may sometimes display overcurrent, overload, or overheat alarms. However, some inverters may not display these alarms and may simply get stuck at a certain frequency range.
2. The V/F ratio is too large.
This parameter, sometimes called torque booster, can sometimes prevent normal startup if set too high. Reducing it appropriately will solve the problem.
3. Vector control parameters mismatch
In vector control mode, parameters such as the motor's internal resistance and inductance need to be precisely measured and matched with the inverter's vector parameters. After running for a period of time, the motor parameters may become overheated and deviate, resulting in excessive current and failure to start the motor normally. The frequency may also get stuck at a certain point. Re-optimizing the parameters can solve the problem.
4. The maximum and highest frequencies are set too low.
These two parameters are usually set to their maximum values, but it's possible that some careless electricians might change them, which could prevent the frequency from being increased.
5. Parameters need to be matched in some special cases.
In some situations, the minimum frequency cannot be set too low. For example, in a constant pressure water supply system, if the minimum frequency is set to 0Hz, when the water pump pressure is low, exceeding the inverter's starting frequency, the inverter will accelerate, but the pressure will never increase. The inverter frequency will never reach 50Hz, only around 38Hz. Repeatedly setting and adjusting the PID controller will not achieve the desired frequency. Only by setting the inverter's minimum frequency to around 15-20Hz can the inverter accelerate sufficiently and maintain the water pump at a constant pressure. Although the pressure meets the constant pressure requirement, when water is not being used, the inverter cannot completely stop and will always maintain the minimum frequency speed.
This is because in a constant pressure water supply system, the lowest frequency of the frequency converter cannot be set to 0Hz, and it is generally at least around 20Hz. This is determined by the flow rate and head of the water pump.
One solution is to set a sleep frequency. When the water pump runs at the frequency it doesn't use (e.g., 28Hz) for a certain number of minutes, it goes into sleep mode. When the pressure drops to 0.2-0.4 MPa lower than the set pressure, the water pump starts again. Another method is to set a timed water supply, supplying water in several time periods. Generally, constant pressure water supply controllers have the functions mentioned above.
6. Hardware issues
When the current transformer (Hall effect sensor) of the frequency converter malfunctions, it cannot measure the correct current, which may also cause a similar situation. In addition, if a measuring component on the main board ages, this situation will also occur. These are common problems encountered when repairing frequency converters.
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