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#166537 - 07/23/07 07:59 AM low volt transformers
falcondfb Offline
Member
Registered: 09/28/02
Posts: 37
Loc: Jersey, USA
I do a lot of dedicated lines for landscape lighting for another company. We have been having problems with inrush tripping breakers.
We have used 1200 watt trans from multiple manufactures but have had trouble anyway. Breaker style or manufacture doesn't seem to matter, although SqD work best.
On the last project that was on a pool panel where the line was 5' long I buried a 50' run of 12/2 UF under ground to provide a cushion and it works well. Anybody have similar problems or solutions besides extending the run?
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#166547 - 07/23/07 12:50 PM Re: low volt transformers [Re: falcondfb]
RODALCO Offline
Member
Registered: 12/08/05
Posts: 854
Loc: Titirangi, Akld, New Zealand
The TX inrush can be up to 20 times the nominal current hence tripping of the MCB.

A way around it is to have a timing device controlling a relay, which at switch on, first put a high power resistor ( ± 4.7 Ohm 50 watts ) in series for about 1 to 2 seconds, than the relay will short the resistor and the TX has normal power applied.

The resistor can be built from five 10 watt 20 ohms ceramic wirewound resistors in parallel in a safe enclosure.

Because of the short interval time the resistors are on for hardly any heat is generated.
Similar systems have been used on high powered amps with large capacitors, when the TX at switch on is feeding basically a dead short at the output for a couple of cycles.
_________________________
The product of rotation, excitation and flux produces electricty.
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#166580 - 07/23/07 06:25 PM Re: low volt transformers [Re: RODALCO]
falcondfb Offline
Member
Registered: 09/28/02
Posts: 37
Loc: Jersey, USA
That sounds great but I am not sure I understand how exactly it works, I have forgotten the parts of "Electricity 1-7" that I don't use often and I am kind of looking for a less involved solution. I was wondering about maybe using a hard start kit for a a/c condenser. Although that might be backward of what I want to accomplish.
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