What should I do if the inverter frequency cannot be adjusted?

The main circuit is the power conversion part that provides voltage and frequency modulation power to the asynchronous motor. The main circuit of the inverter can be roughly divided into two categories:

The voltage type is a frequency converter that converts the DC of a voltage source into AC, and the filter of the DC circuit is a capacitor.

The current type is a frequency converter that converts the DC of the current source into AC, and its DC circuit filter is an inductor. It consists of three parts: a "rectifier" that converts the industrial frequency power supply into DC power, a "smoothing circuit" that absorbs the voltage pulsation generated by the converter and inverter, and an "inverter" that converts DC power into AC power.

Inverter wiring diagram

If the frequency of the inverter cannot be adjusted up and there is no damage to the hardware, it is usually caused by the maximum torque output by the inverter being less than the load-raising torque. To put it bluntly, the inverter's load-carrying capacity is insufficient.

1. The acceleration time is too short

Theoretically, the longer the acceleration time is, the stronger the load-lifting capability will be. If the acceleration time is set too short, some inverters will display overcurrent or overload overheating alarms, but some will not display them and will just get stuck in a certain frequency band.

2. V/F ratio is too large

Some inverters also call this torque boost. If this parameter is set too high, it may not start normally. Reducing it appropriately will solve the problem.

3. Vector control parameters do not match

In the vector control mode, the motor's internal resistance, inductance and other parameters need to be precisely measured and coordinated with the inverter's vector parameters. After running for a period of time, the motor parameters may overheat and cause deviations. This will cause excessive current and make it impossible 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 highest frequency and maximum frequency are set too low

Generally, these two parameters are set to the maximum value, but it is possible that some careless electricians have changed these two parameters, which may result in the inability to increase the frequency.

5. Parameters need to be paired in some special occasions

In some cases, the minimum frequency cannot be set too low. For example, in a constant pressure water supply system, after the minimum frequency is set to 0Hz, when the water pump pressure is low, the inverter starts to accelerate when it exceeds the starting frequency of the inverter, and the pressure can never be increased. The inverter frequency can never be increased to 50Hz, but only about 38Hz. Repeatedly setting and adjusting PID still cannot increase the frequency. Only by setting the minimum frequency of the inverter to about 15-20HZ can the acceleration of the inverter be satisfied, and the water pump can be kept at a constant pressure position. Although the pressure meets the constant pressure requirements, when water is not used, the inverter cannot be completely stopped and always maintains the speed of the minimum frequency.

This is because: in a constant pressure water supply system, the minimum frequency of the inverter cannot be set to 0HZ, and is generally at least around 20HZ, which is determined by the flow rate and head of the water pump.

The solution is to set the dormancy frequency. When the pump runs for several minutes at a frequency (for example, 28HZ) when it is not using water, the pump will go into dormancy. When the pressure drops to 0.2-0.4MP lower than the set pressure, the pump will start. Another method is to set a timed water supply, which can be divided into several time periods. Generally, constant pressure water supply controllers have the above functions.

6. Hardware issues

A similar situation may occur when a problem occurs with the inverter's transformer (Hall device), making it impossible to measure the correct current. In addition, a measuring component on the mainboard may age, which is often encountered when repairing the inverter.