Detecting Typical Faults of Intelligent Power Modules with a Multimeter
The Intelligent Power Module (IPM) is mainly composed of Insulated Gate Bipolar Transistors (IGBTs) and High Voltage Insulated Gate Bipolar Thyristors (IGBTs) as power transistors, combined with driving circuits, protection circuits, etc., as shown in the following figure. Of course, different models of products have different internal functions.
Typical faults:
When anomalies occur, the main points are as follows:
1. The compressor is not running and displaying an abnormal fault code.
2. The compressor is not running, displaying a load current fault code.
3. The compressor is not running, displaying a fault code indicating no circuit or no load.
Note:
There is also a voltage of 12V, so if this type of module is damaged, it will cause the outdoor unit CPU circuit to not work due to lack of power supply, resulting in the air conditioner not working and displaying communication abnormal fault codes.
Fault detection:
There are four main detection methods: visual inspection, voltage measurement, resistance measurement, and substitution method. Using an oscilloscope to measure the output signal waveform will result in better performance. Below are the measurement methods and steps:
Firstly, place the multimeter in the diode mode and measure the forward conduction voltage drop between the U, V, W3 output terminals and the 300V power supply terminal to ground, which is 0.403V. The reverse conduction voltage drop is infinite (the displayed number is 1), as shown in Figure a.
Then, place the digital multimeter in the diode mode and measure the forward conduction voltage drop between the U, V, W3 output terminals and the 300V power supply segment P+, which is 0.448V. The reverse conduction voltage drop is infinite (the displayed number is 1), as shown in Figure b.
Next, place the digital multimeter in the diode mode and measure the forward conduction voltage drop between the U, V, W3 output terminals and the ground terminal P -, which is 0.448V. The reverse conduction voltage drop is infinite (the displayed number is 1), as shown in Figure c.
Schematic diagram of multimeter measurement
If the measured conduction voltage drop is 0 or too small, it indicates that the power transistor has broken down and leaked electricity. If both the forward and reverse directions are infinite, it indicates that the power transistor is open or the internal circuit is open.
