KPC transformer

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greatwestern
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KPC transformer

#1

Post by greatwestern » Thu Feb 06, 2020 4:53 pm

Hi

I have an old KPC Controller TX9 which used to work OK.
Have not used it for some years but looks OK as it is mounted in a wood case.
Went to get it out and have wires that have come off.
I need the transformer to operate a CPU unit to power peco point motors only.
How do I rewire it up to use it for power only for point motors?.
I can see the power comes in to the bottom two tabs but which 2 pairs of tabs on top do I use ?
It hase a pair of tabs, one on left one on right side, both say 16 volts output.
Can I use either of these ?

Mike

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Brian
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#2

Post by Brian » Thu Feb 06, 2020 5:08 pm

Firstly, please be aware mains power at 240 volt is lethal It can cause fires and even kill if not correctly installed.
All mains power transformers should be fuse protected on their Primary mains input - 3Amp fuse.
All transformer secondary windings should be protected by a fuse or self resetting thermal circuit breaker rated at 1.0Amp or 1.6Amp depending on the rating of the transformer. Example of Thermal CB... Link to example
The transformer you're describing has dual secondary (output) windings, each at 16 volts AC.
You connect one pair of outputs (via a fuse or CB in one lead) to one pair of tabs = Output 1. The other pair of wiring tabs are used for output 2 also via a fuse or CB.
A CDU (Capacitor Discharge Unit) has its input connected to one of the transformers secondary outputs.
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greatwestern
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Re: KPC transformer

#3

Post by greatwestern » Thu Feb 06, 2020 5:21 pm

Thank you Brian,
I am aware of safety and at 76 years old take great care.
It does have a 3 amp fuse in line on the mains imput.
Are you saying I need a thermal fuse as per your link ? on the secondary output.
I see that it has two pin treminals, what do they connect to ?.
It is wired for track outputs and accesories,
Only need one outlet for point motors through a CDU unit.
Thank's for your help on this Brian.
Mike

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Brian
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Re: KPC transformer

#4

Post by Brian » Thu Feb 06, 2020 5:33 pm

A fuse or a Thermal Circuit breaker is wired into one lead coming from one pair of output tabs on the transformer.
The fuse or CB is used to protect the secondary winding in the event of an overload or short circuit occurring on that supply feed.
It (the fuse or CB) is wired in series with one output wire, so say for example the Transformers left hand tab goes to one pin of the CB or one end of the fuse. From the other side of the CB or other end of the fuse a wire goes off to the item to be feed. The other tab of that transformers output connects directly to whatever is to be feed. In your case the input of a CDU. Note as the transformer output is AC (Alternating Current) on the tabs of the transformer. So the fuse or CB can be wired into either tab.
Of note....The CDU Input terminals can also be wired either way around as again its AC going in and is converted to DC by onboard diodes or a full wave rectifier on the CDU. The CDUs output is always DC regardless of input.

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greatwestern
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Re: KPC transformer

#5

Post by greatwestern » Thu Feb 06, 2020 5:42 pm

Thank's Brian Iunderstand it all now.

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