Reduced voltage lighting transformer

Checking voltage at a local library to troubleshoot led replacement lamp flicker ,found that the lighting panels are fed from a reduced voltage transformer. It is primary 208 delta to 102/176.8 y . I have never seen or heard of this and no one i talk to has either. Other general receptacle and appliance panels are standard 120/208 . Why would this transformer have ever been used?
 

JFletcher

Senior Member
Checking voltage at a local library to troubleshoot led replacement lamp flicker ,found that the lighting panels are fed from a reduced voltage transformer. It is primary 208 delta to 102/176.8 y . I have never seen or heard of this and no one i talk to has either. Other general receptacle and appliance panels are standard 120/208 . Why would this transformer have ever been used?
Welcome to the forum. That doesnt sound right; the service to the building is 208y/120V, but this transformer is 208V delta? Sounds like a buck boost to convert 240 to 208 (or, here, 208 to 177), but it makes no sense to convert wye to delta back to wye, or to drop the voltage to the numbers you listed.

The xfmr sounds completely unnecessary to me but I dont know. Was the service ever at any point a high leg delta? Maybe the x-fmr was meant to boost 208 to 240 and is wired wonky?

I recall recently seeing a 4' LED tube that accepted an input voltage of 100-280V. Flicker can also be caused by tube/ballast mismatch. Are these 4' tubes, and are they wired off the ballast or do they bypass it and run on line voltage?
 
Its crazy

Its crazy

I know it doesn't sound right but its what they have. The library was built i believe in the 60's. I have the original blueprint that calls for this reduced voltage transformer. The lighting panels are tagged 102v/176.8v. The lighting is surface mounted can fixtures 20' high with 300w incandescent lamps. Now you can see why they tried an led lamp.I have seen led lamps on normal dimmers that blink due to low voltage.Thats what i'm wondering here ,but still curious to know if anyone can explain why a lower voltage for lighting.
 

JFletcher

Senior Member
I know it doesn't sound right but its what they have. The library was built i believe in the 60's. I have the original blueprint that calls for this reduced voltage transformer. The lighting panels are tagged 102v/176.8v. The lighting is surface mounted can fixtures 20' high with 300w incandescent lamps. Now you can see why they tried an led lamp.I have seen led lamps on normal dimmers that blink due to low voltage.Thats what i'm wondering here ,but still curious to know if anyone can explain why a lower voltage for lighting.
What are the actual voltage readings? Is there any information on the types of lights in there now; mfg, ballast info/part#?

I did find light bulbs made to run on 102V:


https://www.bulbamerica.com/products/philips-100w-102v-par38-e26-fl25-4000k-cool-white-mastercolor-cdm-hid-light-bulb-1?CAWELAID=120150920005019746&CAGPSPN=pla&CAAGID=11299126566&CATCI=pla-123078903606&catargetid=120150920000804276&cadevice=c&gclid=Cj0KEQjw6Ya5BRDdyOewyo_Z_64BEiQA-fVKe8_hWq2Wy69UH1K67vOqHez13WLOvPZayFNjvDreK3QaAu7P8P8HAQ

Never heard of them before. To my knowledge, back in the 1960s, voltage was closer to 110 than 120. Still doesnt explain the funky 102V system here tho. I thought Japan used a 100V system; maybe they did back then - my search shows 110V now. Columbia uses a 100V system...

I couldnt find 177V lights, so I'm guessing the 300W bulbs you have are 102V L-N. If this is the case, I dont see why changing them all to standard LED wouldnt work if the step down transformer was bypassed altogether. I dont see an immediate problem directly feeding your lighting panels from the main panels with 208y/120V, unless the lighting panels are only rated 102/177V - what brand of panels?
 

don_resqcapt19

Moderator
Staff member
Given that the reduced voltage is only used to supply high wattage, hard to reach, incandescent lamps, I expect that the design was to make the lamps last a very long time, of course this was done as the expense of lumens.
 

JFletcher

Senior Member
Given that the reduced voltage is only used to supply high wattage, hard to reach, incandescent lamps, I expect that the design was to make the lamps last a very long time, of course this was done as the expense of lumens.
and the expense of a 500kva transformer.. they must have been dirt cheap 50 years ago. I guess 130V bulbs didnt exist/werent common then?

If you are correct, then the xfmr is unnecessary now - it could be bypassed entirely.
 
Will research more

Will research more

Thanks for the replies.Sorry i've been slow responding. The panels are square d. They are switched by individual large contactors. I will investigate the voltage ratings and possibly do away with this old beast of a transformer. If anyone comes up with a good explanation i would like to hear it. Seems crazy to me. Perhaps it was to make the bulbs last longer.
 
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