Variable frequency power supplies are now applicable to various industries,such as home appliances,electronics,and so on.Variable frequency power supply is the process of converting AC power from the mains into pure sine waves through AC-DC-AC conversion.The output frequency and voltage can be adjusted within a certain range.It is different from the variable frequency speed controller used for motor adjustment,and also different from ordinary AC stabilized power supply.During long-term use or due to incorrect operation and lack of attention to cleaning and maintenance,variable frequency power supplies may sometimes encounter some minor problems.
　　Variable frequency power supply is a frequency conversion device composed of the entire circuit,consisting of AC continuous flow,AC filtering,and has been widely used.Variable frequency power supply can not only simulate the power grid indicators of different countries,but also provide pure,reliable,low harmonic distortion,high stable voltage and frequency sine wave power output for export electrical manufacturers in design,development,production,testing and other applications.Variable frequency power supplies are very close to ideal AC power sources and can output the voltage and frequency of the power grid in any country.A frequency converter is composed of circuits such as AC continuous current and AC(modulation wave),and the standard name for a frequency converter should be a frequency converter speed controller.The waveform of its output voltage is a pulse square wave,with many harmonic components.The voltage and frequency vary proportionally and cannot be adjusted separately,which does not meet the requirements of AC power supply.
　　Variable frequency power supply fault one:fuse blown
　　In general,a blown fuse indicates a problem with the internal wiring of the power supply or excessive backend load(surge current).Due to the operation of the variable frequency power supply under high voltage and high current conditions,fluctuations and surges in the grid voltage can cause an instantaneous increase in the current inside the power supply,leading to the melting of the fuse.The key should be to check the rectifier diode,high-voltage filtering electrolytic capacitor,inverter power switch transistor(IGBT),etc.at the input end of the power supply,and check whether these components have breakdown,open circuit,damage,etc.If the fuse is indeed blown,you should first check the various components on the circuit board to see if their appearance has been burnt or if there is electrolyte leakage.If the above situation is not found,use a multimeter to measure whether the switch tube has a breakdown short circuit.It should be noted that when a component is found to be damaged,it should not be replaced and turned on directly.This is likely to cause damage to the replaced component due to other high-voltage components still having faults.It is necessary to conduct a comprehensive inspection and measurement of all high-voltage components in the above circuit before thoroughly eliminating the fault of fuse blowing.
　　Variable frequency power supply fault 2:No AC voltage output or unstable voltage output
　　If the fuse is intact,there is no output of AC voltage at all levels under load.This situation is mainly caused by the following reasons:open circuit and short circuit phenomenon in the power supply,overvoltage and overcurrent protection circuit failure,auxiliary power supply failure,oscillation circuit not working,heavy power load,breakdown of rectifier diode in high-frequency rectification and filtering circuit,leakage of filtering capacitor,etc.After measuring the secondary components with a multimeter and ruling out the situation of high-frequency rectifier diode breakdown and load short circuit,if the output is zero at this time,it can be confirmed that the control circuit of the power supply has malfunctioned.If there is partial voltage output,it indicates that the front-end circuit is working normally,and the fault is in the high-frequency rectification and filtering circuit.The high-frequency filtering circuit mainly consists of a rectifier diode and a low-voltage filtering capacitor to form a DC voltage output.The breakdown of the rectifier diode will cause the circuit to have no voltage output,and the leakage of the filtering capacitor will cause faults such as unstable output voltage.By using a multimeter to measure the corresponding components statically,the damaged components can be detected.
　　Variable frequency power supply fault three:Poor power load capacity
　　Poor power load capacity is a common fault that usually occurs in older or longer operating power supplies.The main reasons are aging of various components,unstable operation of switch tubes,and failure to timely dissipate heat.Emphasis should be placed on checking for heating and leakage of the voltage regulator diode,damage to the rectifier diode,and damage to the high-voltage filtering capacitor.