Improve Voltage Drop Using Capacitor Bank

The first thing is to find out how and why the voltage drop is being caused. That snippet is absent from the original post.

why would you install a capacitor bank?

What is your supply voltage normally and why is it dropping down to 290V? Is it being caused by short term or long term voltage sag due to large loads on the grid switching on?

Depending on your situation a step-up transformer may be a better option, especially if the voltage is continuously lower than you local (400VAC?) supply. Just make sure that the output voltage of the step-up transformer won't go above 460V and damage your AVC.

Recently we have installed 2 No 25KVAR capacitor bank at input side on 2nd Stone crusher where no AVC is installed. When we switched on the capacitor bank the voltage drop decreased from 290V to 300V but when the stone crusher is started the input current increased and the voltage dropped again and crusher motors tripped. We are planning to add more capacitor bank and install a AVC on this crusher so that the voltage drop is decreased by capacitor banks and it comes in the range of our AVC. My question is that will this work?

Not likely!

Your source and transmission cables are to be checked. The drop is too high for these corrections. You are aggravating the condition. The AVC needs to draw more current from the low voltage available at the input, in order to pump the voltage up. ...

I don't think it will. Capacitors help with power factor correction, not voltage sag, so what you are seeing is likely an interaction not a potential fix. I could be wrong, but you need to do more research before spending a lot of money on something that may actually make things worse.

See if you can find the actual cause of the voltage drop, because if your grid supply is too weak causing the voltage sag under load you will need to consider increasing the size of your transformers instead.

If I understood you correctly, you have a 400kVA device (a sort of variable transformer) to stabilize the output voltage. But now the voltage feeding it dropped below its permissible lower limit. Did I understood correctly?

I have to presume, it is a new installation, where you try to maintain proper voltage for a new or expanded old load. Otherwise you would not need it.

Well, I have news for you. When you overload the Grid to the extent, that its voltage sags that badly, after a while no amount of local installation correct the Grid's bad sag.

Get a better, stronger, heftier feed. Then you will not lose a high % of the input voltage.

Dear Mr.bhupinder,

Your post does not indicate 1. the Incput-Voltage to the system. 2. The Load details - whether you use low speed motors and whether highly inductive loads.

Then we can suggest some solution.

DHAYANANDHAN.S

1. Analyze why the voltage dip that big (decrease the voltage to 290V).

2. If you found the reason due to voltage drop, try solve that first or ask your consultant to solve that if you can't.

3. If the problem can't solve, you have two choice, buy the new ones or buy a step up transformer.

The Voltage drop to 290 is too low to correct with a bank of capacitors!

Also, if the input varies wildly from 290 up to 400V, then your problem is elsewhere.

Even a AVC of such a wide input range will not last long with wild variations!

better find out why !

X2. You may be attacking the symptoms not the root of the problem.

Good Luck!