In the application of frequency converter, false load is an important auxiliary equipment, which is mainly used to test and protect the module of frequency converter. In this paper, the principle, application and cautions of frequency converter false load are introduced in detail.

First, the principle of false load inverter

The principle of false load of frequency converter is mainly to protect the module by current limiting resistance to prevent the module from short-circuit resulting in equipment damage. The current limiting resistor can limit the current and protect the module from damage when the module short circuit occurs due to the abnormal driving of the module. The bulb is usually used as a false load, because the bulb has the characteristics of light, you can intuitively judge the working state of the inverter.

Second, the application of frequency converter false load

1. Connection: the false load should be connected between the DC Energy Storage Capacitor and three-phase IGBT, disconnect point to join two 25W 220V-powered bulbs. When there is a problem with the inverter circuit, the bulb has a limited current role in protecting the inverter module. 

2. Power-on process: no-load power-on, according to different conditions to determine whether the module is normal. For example, if a light bulb is lit, there is a problem with the internal insulation of the module; if the power is turned on and there is no problem, but the light comes on as soon as it is running, then there is a problem with an overpass or underpass in a three-phase module. 

3. Trouble shooting: if the power on and running bulbs are not bright, measuring the three-phase output voltage imbalance, it means that a phase IGBT internal open circuit, resulting in increased conduction resistance, close to the open circuit state.

Three，Points for attention

1. The dummy load should be connected between the capacitor and the module, not between the rectifier and the capacitor, because a capacitor discharge can burn out the module. 2. When the switching power supply is after fast melting, can not put the false load on the fast melting, or the light bulb will be bright after power supply, switching power sometimes does not work. 3. The false load is also connected to the DC voltage detection point, so that when the inverter output abnormal light on, the inverter will not jump“Low voltage”, can check which output fault.

Conclusion: inverter false load is a simple and low-cost auxiliary equipment, which can effectively protect the inverter module. However, in the use of the process also need to pay attention to some issues, so as not to affect the test results and the normal operation of the equipment. By using the false load of the inverter correctly, the testing and protection of the inverter equipment can be more safe and reliable.

Source: internet (for study only, intrusion and deletion)