Calculation of SCR and Rectifier Thyristor RC Resistance-Capacitance Absorption Circuit
Choice of capacitance:
C=(2.5-5 times)&TImes;10 to the minus 8th power&TImes;IF
1F=1000Uf 1Uf=1000nF 1Nf=1000pf
If=0.367Id
Id-DC current value
If a 500A thyristor (SCR) is used on the rectifier side, it can be calculated
C=(2.5-5)&TImes;10’s negative 8th power&TImes;500=1.25-2.5F Use 2.5F, 1kv capacitor
Choice of resistance:
R=((2-4) ×535)/If=2.14-8.56 choose 10 ohms
PR=(1.5×(pfv×2πfc) square×10 minus twelfth power×R)/2Pfv=2u(1.5-2.0)
u=effective value of three-phase voltage
The time constant of RC is generally 1~10 milliseconds.
Low power load usually takes about 2 milliseconds, R=220 ohm 1W, C=0.01 microfarad 400~630V.
High-power load usually takes 10 milliseconds, R=10 ohm 10W, C=1 microfarad 630~1000V.
The choice of R: choose metal film or RX21 wire wound or cement resistor for low power; choose RX21 wire wound or cement resistor for high power.
Selection of C: CBB series of non-polar capacitors with corresponding withstand voltage.
Look at the protection object to distinguish: the damping absorption of the contactor coil and the damping absorption of the thyristor with a current less than 10A are included in the low-power category; the damping absorption of the contactor contact and the thyristor with a current greater than 10A is included in the high-power category.
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