The circuit of Universal Variable Frequency drive

- Sep 07, 2017 -

① lightning protection circuit: when there is lightning, resulting in high voltage through the power grid into the power, by the MOV1, MOV2, MOV3: F1, F2, F3, FDG1 circuit protection. When the voltage applied to both ends of the varistor exceeds its operating voltage, its resistance decreases, so that high voltage energy consumption in the varistor, if the current is too large, F1, F2, F3 will burn the protection of the secondary circuit.
② input filter circuit: C1, L1, C2, C3 composed of double π-type filter network is mainly on the input power of the electromagnetic noise and clutter signal suppression to prevent interference to the power supply, but also to prevent the power itself generated high-frequency Wave to grid interference. When the power is turned on, to C5 charge, due to instantaneous current, plus RT1 (thermistor) can effectively prevent the inrush current. Due to instantaneous energy consumption in the RT1 resistance, after a certain period of time after the temperature increases RT1 resistance decreases (RT1 is the negative temperature coefficient components), then it consumes very little energy, after the circuit can work properly.
③ rectifier filter circuit: AC voltage by BRG1 rectifier, the C5 filter to be more pure DC voltage. If the C5 capacity becomes smaller, the output ripple will increase.

Ac input rectifier filter circuit principle.png

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① input filter circuit: C1, L1, C2 composed of double π filter network is mainly on the input power of the electromagnetic noise and clutter signal suppression to prevent interference to the power supply, but also to prevent the power itself generated high-frequency clutter Grid interference. C3, C4 for the safety capacitor, L2, L3 for the differential mode inductance.
② R1, R2, R3, Z1, C6, Q1, Z2, R4, R5, Q2, RT1, C7 constitute the anti-surge circuit. At the moment of starting, because the existence of C6 does not turn on, the current circuit formed by RT1. When the voltage on C6 is charged to the Z1 regulator, Q2 turns on. If the C8 leakage or post-circuit circuit short-circuit phenomenon, the instantaneous current in the RT1 generated on the voltage drop increases, Q1 conduction makes Q2 no gate voltage is not conducting, RT1 will be burned in a very short time to Protect the post-stage circuit.

Dc input filter circuit principle.png

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