Transformer rewind wire query

[Spike1947]

Hi
I have a Transformer, that needs a rewire on a Secondary windings, the wire that was on it, was a muti-core wire 9 strands, (0.06mm x 9) ( each strand enameled ), soldered together at each end, and laid on top of the primary winding with 175 turns, with a copper tape between the primary and this secondary .

Question: This multi core (Litz) secondary winding is supposed to have a output of 420v, but with only175 turns it will not equate to 420v, but if all the strands of the Litz was classed has a single turn then that will equate to 420v !.

I just don't get it .

Transformer outputs are:

Primary: 0: 0 – 240. V, P1,P2,P3
Secondary 1: 0 – 420. V @ 3 mA , S3
Secondary 2: 0 – 6. V @ 32 A , S1
Secondary 3: 0 – 12. V @ 400 mA, S2

Cheers
Spike
ps: think this might have been posted twice !

 

[Spike1947]

I wondered if the two electrolytics were in series (with resistors across) to get the voltage rating, as they look quite small!

I'm concerned at the idea of moving/re-soldering the resistors. If they've got really hot, the growth of intermetallic compounds in the solder has made the joints brittle and they will be difficult to work on, and the reliability will just get worse and worse with tinkering!
Am I worrying unnecessarily?
If it's arc splash rather than heat then maybe.

 

[Spike1947]

Hi
I don't see a problem in raising the ceramic resistors away from the board and the relay, the new solder will replace what is there !.

I am wondering if, with the secondary winding that is laid on top of the primary , could it pick up any voltage from the primary !.

Spike

 

[Avo Mk8]

Hi
Yes you are correct, is that condoned ?, I do keep looking on ebay, but would rather see if I can sort it myself though, bit of a challenge tbh.
Spike

You obviously enjoy a challenge - but I was thinking another one for parts might be an overall cheaper and more reliable way of obtaining spares (eg a transformer!).

Do you know if the electronics still works?
If not, have you considered re-instating the transformer without the 425V winding, and seeing if the thing has survived? Or using a bench psu to run it? It would surely be frustrating to rewind the transformer only to find a trail of further issues?

 

[Avo Mk8]

Hi
I don't see a problem in raising the ceramic resistors away from the board and the relay, the new solder will replace what is there !.

You may find the solderability has become very poor, and difficult to get solder to flow to make a proper joint. It may not matter to you, but in the commercial world it's a concern, as the joints become unreliable.

I am wondering if, with the secondary winding that is laid on top of the primary , could it pick up any voltage from the primary !.

'pick up' only in the sense that insulation between the primary and secondary could break down. Thats why you need the layers of yellow polyester tape insulation between the two - as per your pics?

 

[Spike1947]

You obviously enjoy a challenge - but I was thinking another one for parts might be an overall cheaper and more reliable way of obtaining spares (eg a transformer!).

Do you know if the electronics still works?
If not, have you considered re-instating the transformer without the 425V winding, and seeing if the thing has survived? Or using a bench psu to run it? It would surely be frustrating to rewind the transformer only to find a trail of further issues?

No I don't, but that is exactly what I am going to do see post #18., then connect it up if I am getting a reading on the secondarys

Spike

 

[marconi]

If I employed someone to do some statutory periodic PAT testing for a fee and he/she turned up and used a PAT tester which they had repaired themselves after clear and major damage - I would refuse to pay them. And consider what else to do.......

But you may be doing this 'for fun' to see if you can get it working again and then you intend to bin it because the integrity of this test equipment is shot.

 

[Spike1947]

You obviously enjoy a challenge - but I was thinking another one for parts might be an overall cheaper and more reliable way of obtaining spares (eg a transformer!).

Do you know if the electronics still works?
If not, have you considered re-instating the transformer without the 425V winding, and seeing if the thing has survived? Or using a bench psu to run it? It would surely be frustrating to rewind the transformer only to find a trail of further issues?

No I don't, but that is exactly what I am going to do, see post #18, then connect it up if I am getting a reading on the secondarys

If I employed someone to do some statutory periodic PAT testing for a fee and he/she turned up and used a PAT tester which they had repaired themselves after clear and major damage - I would refuse to pay them. And consider what else to do.......

But you may be doing this 'for fun' to see if you can get it working again and then you intend to bin it because the integrity of this test equipment is shot.

Hi
Thanks for your reply, yes it is purely a challenge for me, and believe me I like a challenge , it also won't get into anyone elses hand, so def you won't be paying me to do any PAT Testing for you, actualy they don't use that term now, in the 18th edition it is called "Appliance Testing" , didn't include static Appliances but now does, so don't lose any sleep over it .

Spike

 

[Spike1947]

You may find the solderability has become very poor, and difficult to get solder to flow to make a proper joint. It may not matter to you, but in the commercial world it's a concern, as the joints become unreliable.

'pick up' only in the sense that insulation between the primary and secondary could break down. Thats why you need the layers of yellow polyester tape insulation between the two - as per your pics?

No, I meant any magnetic flux etc !.

 

[Lucien Nunes]

In an ideal transformer all the flux links all the windings. In practice the coupling is not perfect, hence leakage reactance. The physical arrangement thus affects the regulation and efficiency slightly, but not the the transformation ratio.

 

[marconi]

ps: The primary has roughly about 800 turns, 399 for the first layer !.
pps: Pic of PAT Tester board that the transformer feeds , it does a 500v DC test ! .

Spike