General Electrical / Electronics

Thread Starter


Joined Oct 5, 2017
I do apologize if this is not the right place to post.

1. There is a power factor improvement box currently improving power factor of some 750MVA load. The power factor that it is keeping is about 0.95. It is about 20-30 years old (the whole module). There is no documentation available about the type of capacitors being used or the DC voltages or ripples etc.
As the capacitor bank is old, I want to know if it is still safe to use those capacitors. If there needs to be a life cycle test / replacement for those. If so, what can I do ?
What sort of capacitors would they be if they are being used for that much load?
What is the average life cycle of those capacitors that are being used in industries (in general)
How often does one replace capacitors?

What happens if they get too old and are not replaced?
Do they explode? if so? what causes them to do so?
Any suggestions will be appreciated.

2. The voltages of a bus bar are same at each tapping. However, a few manuals that I read suggest that the voltages of a machine (lets say a boiler or a chiller) be taken on the machine and not on the bus bar. Is it possible for bus bar voltages to be different from the machine voltages? Incase of a fault?

3. What are the important components / electronics in a control panel / distribution panel (for machines / houses , control rooms) that should be checked/tested/maintained against a standard?


Joined Nov 18, 2016
The place to ask about this is power electronics, but it does not matter. This is mostly middle voltage electrical grid in my country.

1. When you say power factor, I am thinking of AC power factor, real and fictive power. Those should not be DC voltages, unless the device transforms the voltages to DC and then back to AC.

There are ways to check if the capacitors need to be replaced, if something is old, that means its quality is higher and there should be some life expectancy for this device (10 years, 20 years and so on). What is your electrical skill, do you know how to use tools and understand measurements?

2. The voltages on the machine can be different, there are problems that can occur here, unstable potential is something met.

4. There is always a chance of a burned capacitor to catch fire, but it is not like they explode.