Autotransformers and LED lights

Status
Not open for further replies.

mitchfrompei

Member
Location
pei
Currently doing a job where 63 LED pot lights came in 120v when they were suppose to be 347v. The solution from my boss was to get a 395va auto transformer for each pot light. So I wired each auto transformer to the LED pot light. This is spread over two 15a 347 breakers. How ever, without the potlight inserts (the LED LIGHT) the breakers are reading about 7amps with no load? I traced the wires out as they are existing, and they only feed the pot lights I installed.
 

mpoulton

Senior Member
Location
Phoenix, AZ, USA
Currently doing a job where 63 LED pot lights came in 120v when they were suppose to be 347v. The solution from my boss was to get a 395va auto transformer for each pot light. So I wired each auto transformer to the LED pot light. This is spread over two 15a 347 breakers. How ever, without the potlight inserts (the LED LIGHT) the breakers are reading about 7amps with no load? I traced the wires out as they are existing, and they only feed the pot lights I installed.

Wait, so each little fixture has its own 395VA transformer? A total of 25kVA of transformers? Not surprised by the 7A magnetizing current, with so many little transformers. Why not use two transformers, one for each circuit? Less magnetizing current, cheaper, less labor... too late now, it seems.
 

mitchfrompei

Member
Location
pei
Wait, so each little fixture has its own 395VA transformer? A total of 25kVA of transformers? Not surprised by the 7A magnetizing current, with so many little transformers. Why not use two transformers, one for each circuit? Less magnetizing current, cheaper, less labor... too late now, it seems.

Agree, but not my call. I suppose this current is going to affect my max current? IE, if I need 12 amps per circuit, and they're already at 7amps?
 

GoldDigger

Moderator
Staff member
Location
Placerville, CA, USA
Occupation
Retired PV System Designer
Agree, but not my call. I suppose this current is going to affect my max current? IE, if I need 12 amps per circuit, and they're already at 7amps?

Yes and No. The 7 amps is at close to zero power factor. The current to drive the LEDs will be at a power factor of 1. They will add vectorially to less than the sum of the two numbers.
But that is indeed the penalty for using a 395VA transformer to drive a no more than 50VA load.
 
You are using a 395va tranny to drive such a tiny load ?
Your crazy !
Put more than one light on each tranny
you should get easily 10 lights per tranny.
Otherwise send the lights back,
or at least send the drivers back
Your Boss is just plain crazy !

:slaphead:
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
Occupation
retired electrician
If I am the owner, you are not going to put the transformers in....I would be paying for the transformer losses forever....you would have to install the correct voltage fixtures.
 
Status
Not open for further replies.
Top