Central Tap

There is no problem as such.

OLTC can be operated on any tap, continuounly. The taps are provided to maintain secondary constant. Normaly this would increase/decrease 1.25% secondary voltage.

the problem of having the OLTC at center tap is that, you may experience low voltage at your secondary side..

OLTC is designed to make your secondary voltage level to almost 100% constant. however, if you are only to set the tap at the center, then when your supply voltage is low, you would experience low voltage. OLTC is designed to minimize this low voltage..

by the way, what is your objective to set it regularly on center tap?.. doesn't make sense if you are having OLTC.

sir let me know the reason for the low voltage in the secondary

the reason for low voltage is your load.. the greater the load is the lower the voltage gets..

try to do.. load flow studies.. and experiment on this..

when the secondary voltage gets low.. the OLTC will detect this, and change the ratio of the transformer to maintain the secondary voltage..

I've had it cause problems. The transformer wasn't deliberately set on one particular tap setting, the drive motor for the changer mechanism had tripped on overload without anyone noticing. We ran for months with it like that, the problems started when some new VFD drives were installed. The drives were installed mid week while the transformer was under normal load. At the weekends the reduced loading caused the voltage to rise damaging the new drives. So as they were under warranty the vendor replaced them. They ran all week OK, come the weekend, drives damaged again. The vendor replaced them yet again but was getting very wary as to what was going on. Checking the voltage at the w/e what should have been 11KV was nearer 11.7KV.

It is a furnace transformer and we r not using continuously on tap 8.We r now avoiding completely the 8 th tap

Pl. describe process of using transformer for induction furnace.

How can you avoid a particular tap in OLTC. 8th tap in your case

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Quote:

What is the problem of running with central tap of a transformer. (OLTC has 17 taps,can I use tap position 8 regularly)

Make up your mind!

Tony,

not you, the person asking question