High leg incoming service - 3 phase 2legs 120 0ne leg 210V

Question

High leg incoming service - 3 phase 2legs 120 0ne leg 210V

guest0821 (visitor)

(OP)

11 Nov 00 19:04

On a incoming service 3phase 240V phase to Phase. 2 legs
are 120 against neutral one leg is 208 V.
The incoming service is 600 A. The high leg has only a 15
HP compressor connected. The air compressor cuts in and out. I am trying to correct the PF which is .85 and .90
on the legs used for lighting etc. and .14 at no load on the
high leg when the compressor runs the PF is .75 [high leg]
the monthly power consumption is 8000 Kwh. Kw demand is 24.
What can be done to improve the power factor on this system.
The voltage THD is 7.5%. The amperage THD is 17%.
Thank you
Have a nice Day
Fritz <LiteIt@ptd.net>

jbartos (Electrical) · Answer 1 · 2000-11-12 13:55:31

The power factor capacitive compensator may help, e.g. by ABB, Electrotek, etc.

**guest0821** (visitor) · Answer 2 · 2000-11-13 06:11:17

j bartos thank you. can not locate :ABB nor Electrotek.
please provide E Mail address or Phone#
Thank You and have a nice day.
<LiteIt@ptd.net>
Fritz

jbartos (Electrical) · Answer 3 · 2000-11-13 06:41:17

1-800-404-9114 for Electrotek, Ltd.
01-919-856-2390 for ABB, Mr. Eric John, email: eric.john@ustra.mail.abb.com

CurtJ (Electrical) · Answer 4 · 2000-11-14 08:27:38

I'm wondering if you are measuring the power factor correctly. What you have here is a delta connected transfomer bank with one of the windings center-tapped for the neutral. The two 120 volt legs can be used for single phase loads such as lighting and office equipment. The high leg, which measures 208 volts line to neutral, should never be used for single phase loads connected line to neutral. This high leg is for three-phase loads, only. If you are measuring the power factor on the high leg using a line to neutral voltage connection, you will get a wrong reading.

**guest0821** (visitor) · Answer 5 · 2000-11-14 21:16:23

Curt J Thank you.

Why can the high leg be used as straight 208 V single Phase,
or with help of a transformer be used as 120/240 V ?
I have a 200A 3 phase service and the high leg is used for
a 15 HP air compressor and nothig else.
Would it not be better for the system if the high leg was
loaded ? It would increase the available power.
Am I wrong in assuming this?
Thank and have a nice day.
LiteIt Fritz
<LiteIt@ptd.net>

CurtJ (Electrical) · Answer 6 · 2000-11-27 08:36:09

The high leg can be used as a source for 208 volt single phase loads, but I wouldn't recommend it. Without doing a full circuit analysis of the situation, I'm not sure how much load would be imposed on each of the transformers. I would also have to know how the transformers are connected. If this is an open-delta bank, I'm sure that you would have voltage regulation problems.

Come Join Us!

Posting Guidelines

High leg incoming service - 3 phase 2legs 120 0ne leg 210V