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# How to choose the charging resistance value?

Aug 14,2020

380 v alternating current (ac) after rectification after charging resistance of electrolytic capacitor charging, when the charge to a certain value (such as DC200V) auxiliary power start to panel power supply, make control panel to relay or thyristor switched on, the charging resistance is no longer work.In the boot of the moment, the charging resistance is smaller, the greater the current through the rectifier bridge.Often have a beginner's inverter WeiXiuZhe telephone consultation, replace the charging resistance, frequency converter, a boot, rectifier bridge was blown up immediately, charging resistance selection is too small?The answer is no.

Actually, on the instant, usually a boot blow up the rectifier bridge not because choose charging resistance R small, but R is too big lead to blow up the rectifier bridge.Because the frequency converter after startup, electricity flows through the charging resistance to charge, when filling the electricity auxiliary power enough start (such as 200 v), CPU, signal for relay and thyristor SCR conduction.In relay conduction instantaneous relay point b if the voltage is very low (greater than 200 v), and a point is AC380V voltage rectifier around come around DC540V directly, so a, b two terminal pressure difference is very big.In trigger, conduction current is very big, like between a and b is a small resistance, instantly add in a few hundred volts, such a rectifier bridge through the electric current is more than rated current rectifier bridge, so the rectifier bridge blown up.

The smaller the inverter power, the greater the charge resistance.Because the inverter power, the greater the need to the greater the capacity of electrolytic capacitor, and the capacity of the capacitor, the greater the need to recharge the longer it will be.RC decided to charge time, want to charging time is short, as far as possible only take small charge resistance R.In charge resistance choices: had better not more than 300 Ω maximum, minimum value is greater than or equal to 10 best Ω, high-power inverter choose charging resistance is small, small power converter charging resistance.

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