Three Phase Rectifier Capacitor

[maheshyedla]

A 3 phase 240VAC line and I get a max output voltage of 589Vdc.
designing the circuit for 100KVA.

After the three phase rectification my output voltage is 589Vdc, after these I need to place a capacitor branch at dc side. So how to calculate the Capacitor value.

Can any help me how to calculate the capacitor value at dc side of the 3 phase rectification and also if possible with some equations.

Thanking you in advance.

Best Regards,
Mah

 

[johansen]

This sounds like a homework problem, because you left out all the critical information. What you are doing with the 589 volts?

 

[Jaguarjoe]

You'll need to know the load current because the cap will be supplying that current between the voltage peaks from the bridge.
If you manipulate I = CdV/dT you should be real close.

 

[tcmtech]

Things are not adding up already. 240 VAC 3ph rectified should have peak voltage of 340 volts DC not 589.

If you have 589 VDC you are running off of a 416 VAC circuit which could be possible if its a 240/416 Wye system.

At 100 Kw on 589 volts you would be drawing around 170 amps. Without knowing what load you are running a rough guess would be that you would need between 40,000 and 100,000+ uf.

Don't drop your screwdriver on the buss bars when thats charged up!

 

[WTP Pepper]

The sums suggest you are going across phases.
240AC RMS x Sqrt(2) gives you a peak voltage. Then multiply by sqrt (3) gives you your voltage of approx 588V.
Jaguarjoe is correct. You need to know the current being drawn and the suggested equation is a good start.

 

[maheshyedla]

Actually I am doing the simulation work for Resistance Welding Current Transformer for IBE Robots.

3-Phase Rectification , capacitor branch, Full Bridge Inverter, Transformer and then the rectification. I have designed the circuit. Vrms is 400V,50Hz. Designing for 100KW power.

Now my doubt was how can I calculate the capacitor value in capacitor branch,

I am attaching my project circuit to this thread.View attachment 63368View attachment 63368

 

[maheshyedla]

Hi Pepper,

You are write. I have calculated the DC voltage as what you said. I am designing for 100KW power.