Inverters can be categorized into low-voltage and high-voltage inverters based on their input voltage level. Common low-voltage inverters in China include single-phase 220V inverters. To enhance understanding of inverters, this article will introduce methods for handling inverter interference and short-circuit problems in inverter ICs. If you are interested in inverters, please continue reading.
I. Solutions to Inverter Interference
Electrical processing plants have extremely high requirements for the working efficiency of their machinery. Therefore, many electrical processing plants install and use frequency converters to ensure that the efficiency of their machinery meets production needs. Because these plants use a wide variety and large number of different types of machinery, frequency converters are easily susceptible to interference during production. Once a frequency converter is interfered with, its working efficiency will be severely affected.
If signal interference is detected during the use of a frequency converter, it is necessary to first determine the source of the interference signal and take appropriate measures to block the signal interference based on the actual situation. Alternatively, certain methods can be taken to prevent the frequency converter from being interfered with, making the frequency converter more stable during operation.
Frequency converters are generally susceptible to interference from radiation during operation. If a frequency converter is interfered with by radiated signals during production, the interference signal needs to be propagated through radiation. This is achieved by weakening the interference signal through wiring and by shielding the radiation source and the lines being interfered with.
If the frequency converter is affected by interference signals propagating through the lines, it needs to be addressed by installing filters on the input and output sides of the frequency converter, or by using reactors or magnetic strips. Specifically, signal lines and power lines can be routed in separate channels at perpendicular intersections. The shielding conduit should be grounded as much as possible, and a continuous and reliable grounding should be maintained along its entire length.
Inverters are susceptible to line-borne interference. Therefore, the shielding layer should be grounded away from the inverter and kept at a distance from the inverter's grounding point. To further mitigate interference, a ferrite core can be used on both the inverter's input and output power lines. The input lines and output lines should be wound in the same direction, and the ferrite core should be kept close to the inverter during winding to prevent interference.
II. How to handle a short circuit in the inverter IC
A frequency inverter can normally last up to 10 years. However, various external factors can reduce its lifespan. Various inverter malfunctions can further shorten its service life. In fact, short-circuit faults in the inverter's IC circuitry can be easily resolved without affecting its lifespan.
A short circuit in the inverter IC causes intermittent oscillation in the switching power supply, and the operation display panel flickers on and off. This is a typical fault indicating that the switching power supply is overloaded or short-circuited. The abnormal load triggers the protection mechanism of the switching power supply's current detection circuit, causing the switching power supply to oscillate intermittently.
Methods for detecting short circuits in inverter ICs: Disconnect the load circuits one by one to troubleshoot which load circuit is causing the short circuit. Alternatively, after a power outage, measure the output terminals of each power supply circuit for decreased resistance or short circuits. Measuring the +5V power supply terminals showed a low resistance of 7.8Ω, while a normal circuit would have a resistance of several hundred Ω. This indicates a short circuit in the +5V load circuit. Disconnecting the +5V load circuit and then providing a stable output from the switching power supply confirms the fault lies in the +5V load circuit. The +5V power supply goes from the ribbon cable terminals to the CPU motherboard, supplying the CPU chip and peripheral circuits. The circuit range is quite wide, with many integrated circuits on the CPU motherboard providing +5V power, numbering over twenty. To check for short circuit faults in the inverter using conventional elimination methods, the +5V power supply pins of each IC circuit must be disconnected. This is combined with testing the resistance value at the power output terminal. When the resistance value at the power output terminal changes from the low 7.8Ω value to the normal value after disconnecting a power supply pin of an IC, it indicates that the IC has a short circuit fault. Of course, measuring the resistance value of the power supply pin after disconnecting it yields the same result.
It's impossible to predict how many ICs will need to be removed to find the faulty IC in the inverter. The soldering precision of the CPU motherboard components is almost comparable to that of a mobile phone circuit board. The IC circuits are all surface-mount components, and the copper foil strips on the IC pins are thinner than a hair—that's not an exaggeration. If you accidentally remove a copper foil strip, reconnecting it is difficult; picking them one by one is too inefficient. Because the inverter's switching power supply itself has limited load capacity, connecting it to a faulty circuit will trigger overcurrent protection, causing the power supply to stop outputting. Therefore, a larger capacity +5V power supply is used, connected in series with a 5Ω 5W current-limiting resistor to the CPU motherboard. After powering on for a few minutes, touch the IC chips on the CPU motherboard; the one that is hot to the touch and shows an abnormal temperature rise is the faulty IC.
