So ermitteln Sie mit einem Multimeter die Qualität der Wechselrichter-Gleichrichterbrücke
1. Test rectifier circuit
Set the multimeter to resistance X10, connect the red probe to the P terminal, and connect the black probe to the R, S, and T terminals in sequence. There should be a resistance value of about tens of ohms and it should be basically balanced. Connect the black probe to the P terminal, and then connect the red probe to R, S, and T in sequence, with a resistance value close to infinity. Connect the red probe to the N terminal and repeat the above steps. The same result should be obtained. If the resistance values of the three phases are unbalanced or if the red probe is connected to the P terminal and the resistance is infinite, it can be determined that the circuit has malfunctioned and the rectifier bridge is faulty.
2. Test the inverter circuit
Connect the red probe to the P terminal, and then connect the black probe to U, V, and W in sequence. There should be a resistance value of several tens of ohms, and the resistance values of each phase should be basically the same. Connect the black probe to the P terminal, and then connect the red probe to U, V, and W in sequence, with a resistance value close to infinity. Connect the black probe to the N terminal and repeat the above steps to obtain the same result, otherwise it can be determined that the inverter module is faulty.
The power on test can only be carried out after the rectification circuit and inverter circuit have been tested and found to be normal. Determine the fault and its cause based on the displayed fault information before and after power on.
Analysis of Damage Causes:
(1) The quality of the device itself is poor;
(2) The damage to the secondary circuit and inverter power switching devices resulted in the rectifier bridge being damaged due to the flow of short-circuit current;
(3) The voltage of the power grid is too high, causing lightning strikes and overvoltage surges. The internal resistance of the power grid is small, and the varistor for overvoltage protection has burned out and is no longer effective, resulting in all overvoltage being applied to the rectifier bridge;
(4) The frequency converter is too close to the power transformer of the power grid, and the impedance of the middle line is very small. The frequency converter is not equipped with DC reactors and input side AC reactors, which puts the rectifier bridge in a high amplitude sharp pulse current impact state of capacitor filtering, causing premature damage to the rectifier bridge;
(5) Input phase loss increases the burden on the rectifier bridge and causes damage.
Identify the root cause of the damage to the rectifier bridge and eliminate it to prevent further damage when replacing it with a new rectifier bridge.
(1) Replace the rectifier bridge with a new one and ensure reliable welding of the welded rectifier bridge. Ensure electrical safety distance from surrounding components and tighten screws to prevent high contact resistance and heat generation. For those that conduct heat to the radiator, it is required to apply silicone grease to reduce thermal resistance;
(2) For parallel rectifier bridges, products of the same model and manufacturer should be used to avoid damage caused by uneven current.
1. The detection of half bridge is composed of two rectifier diodes. By measuring the positive and negative resistance values of the two diodes inside the half bridge with a multimeter, it can be determined whether the half bridge is normal.
2. Full bridge detection: Most rectifier full bridges are marked with "+", "-", and "~" symbols (where "+" is the positive pole of the rectified output voltage, "-" is the negative pole of the output voltage, and "~" is the AC voltage input terminal), making it easy to identify each electrode.
When detecting, the positive and negative resistance values of each rectifier diode between the "+" pole and two "~" poles, and between the "-" pole and two "~" poles can be measured separately (using the same measurement method as ordinary diodes) to determine whether the full bridge is damaged. If the forward and reverse resistance values of the whip diode in the entire bridge are both zero or infinite, it can be determined that the diode has broken down or is open circuit damaged.
