GT MCC module has 240 V AC control supply and 125 V DC indication supply

G

Thread Starter

GIRISH

Dear sir,

I am working in CPP with 750 MW power generation capacity. There are 6 gas turbine generators. GT MCC of all the generators has 240 V AC for control circuit and 125 V DC for indication circuit. (10 modules have 4 electronic circuits with 4 LEDs.) So my question is, what are the reasons for having two different supplies for control and indication circuit?
 
There could be lots of reasons. I would also submit that there are other circuits using 24 VDC or 24 VAC that you may not be aware of. There's even probably some 0-5 VDC circuits, as well as some 1-5 VDC or 0-10 VDC circuits.

The reasons for using any voltage are related as much to what voltage(s) is/are available as to what voltage is required. It's pretty common for most MCC applications to use 120 VAC or 240 VAC in their control circuits. (DC motor starters usually use DC in their control circuits.) This is basically a function of what the MCC manufacturer provides or is asked to provide.

Sometimes, the voltages used reflect the restrictions in the area where the devices it interacts with are located, such as hazardous locations or atmospheres.

There is no "rule" or "standard" which says this or that voltage must be used exclusively. It's one of the joys of working in a large plant to have to deal with and have spare parts for a multitude of voltages and current levels!
 
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