Toroidal Transformer Insulation Rating

[316a]

Hello Folks !
I can't find my megger but need to know the insulation rating of a transformer . Unit is a 115/115 primary 50VA Talema , unable to find the info on the website , would guess much-of -a-mutchness between manufacturers . Any ideas ? Thanks for your time

316a

 

[tiroth]

http://www.amveco.com/Power_Transformers.htm

Low Profile PC Mount:
Safety standard certifications (UL 506, UL 1950, UL File E122978, E138299)
VDE 0805, IEC 950, EN 60950
UL recognized for insulation Class A (105C). Meets all requirements of Class E(125°C)
Hipot testing at 4000V between primary and secondary. (VDE0550)
Maximum ambient temperature of +60°C for 1.6VA-25VA, +40°C for 35VA and 50VA models

Low Profile Miniature:
Safety standard certification (UL 506).
UL recognized for insulation Class A (105°C). Meets all requirements of Class E(125°C)
Hipot testing at 4000V between primary and secondary.
Maximum ambient temperature of +60°C

Is that what you needed?

 

[316a]

Thanks !

Well spotted , could not find the info myself .

316a

 

[ScottRHinson]

Re: Thanks !

Well spotted , could not find the info myself .

316a

May I enquire as to why you needed this information? If you are planning on using a transformer beyond it's rated capacity (IE use this transformer in a tube circuit) I would suggest that you not do this.

Scott

 

[316a]

Why not ?

I have used toroids for the last year succesfully in push-pull , parafeed and recently driving small ESL panels **without** problems . The only 'problem' is the bass driving cone drivers which is a tad light but who cares with a >1khz ESL panel ! I'm about to build a 20 x 36" panel which will require substantially higher drive (2500v p-p) hence the query and I doubt I'll be able to get enough drive directly from the amp's anodes . Why would toroids be a poor choice in your view ? When I find my megger I'll run some more tests to concur with the info on the Talema site

316a

 

[ScottRHinson]

Re: Why not ?

I have used toroids for the last year succesfully in push-pull , parafeed and recently driving small ESL panels **without** problems . The only 'problem' is the bass driving cone drivers which is a tad light but who cares with a >1khz ESL panel ! I'm about to build a 20 x 36" panel which will require substantially higher drive (2500v p-p) hence the query and I doubt I'll be able to get enough drive directly from the amp's anodes . Why would toroids be a poor choice in your view ? When I find my megger I'll run some more tests to concur with the info on the Talema site

316a

Hmmm..it's typically a safety thing. The reasons that any transformer is tested to say 4000V hi-pot is to show a sufficient safety margin for the insulation. The insulation that passes for such a test will be very safe at lower voltages over a very wide range of temperatures and humidity levels.

Scott

 

[316a]

What problem ?

Hello ,
Nothing to worry about , here in the UK , the weather is less variable than your side of the pond , what humidity ? Tx has been running for the last 30 mins , no heat , no fuss the **wrong** way round . I'm getting 1200v across the primary via isolating transformer on the secondary . With a 400V valve HT transformer I'm getting 1808V , same again , no problems , sparks , heat or near death experiences . The megger test will be the decider though .

316a

 

[dhaen]

Safety or performance?

The critical point here is surely:

If the transformer were to break down, would it cause any safety hazzard, or just a horrible noise.

If the former - don't. If the latter, no problem.

Cheers,

 

[316a]

Re: Safety or performance?

The critical point here is surely:

If the transformer were to break down, would it cause any safety hazzard, or just a horrible noise.

If the former - don't. If the latter, no problem.

Cheers,

I doubt anything really bad would happen , the latter will probably be the case at worst , I've only seen transformer insulation break down due to heat in the past . Arcing is the main enemy at these voltages


316a

 

[316a]

Re: Safety or performance?

The critical point here is surely:

If the transformer were to break down, would it cause any safety hazzard, or just a horrible noise.

If the former - don't. If the latter, no problem.

Cheers,

I've only seen transformer insulation break down due to heat in the past usually within telecoms equipment that had been switched on since the year dot surely a fus on the HT rail should do the trick ?

316a

 

[ScottRHinson]

Re: Safety or performance?

The critical point here is surely:

If the transformer were to break down, would it cause any safety hazzard, or just a horrible noise.

If the former - don't. If the latter, no problem.

Cheers,

The answer is yes. ;-) Frankly I feel that it would cause both. Fire and/or component damage is possible and probable.

Scott

 

[ScottRHinson]

Re: Re: Safety or performance?

I've only seen transformer insulation break down due to heat in the past usually within telecoms equipment that had been switched on since the year dot surely a fus on the HT rail should do the trick ?

316a

I honestly don't know. I've never run a transformer that hard unless it was meant to, or I was using a hi-pot tester that had a good current limit on it, so there wasn't a chance for a hazard. (Possible destruction of the device.....but anyway.)

Scott

 

[dhaen]

I doubt that a transformer, if properly fused, could cause a fire risk in that application. Fire from transformers used to most often be caused by emission of flamable gasses, during overheating. This doesn't happen with approved transformers now.

What I was concerned about was electric shock hazzard, if the thing did break down, or just arc'd.
Can the centre-tap of the (new) secondary be earthed?

Cheers,

 

[316a]

Insulation

I doubt that a transformer, if properly fused, could cause a fire risk in that application. Fire from transformers used to most often be caused by emission of flamable gasses, during overheating. This doesn't happen with approved transformers now.

What I was concerned about was electric shock hazzard, if the thing did break down, or just arc'd.
Can the centre-tap of the (new) secondary be earthed?

Cheers,

If I earth the centre-tap I'd have to fully insulate the panel instead of just adding a cover to the rear . Insulating the panel would loose sensitivity unless I increased the polarising voltage / drive to compensate . If the thing would break down , the output stage would see a short or partial short , crackle-pop-no music . Considering many ESL builders use vintage valve output transformers the same way , with **unknown** insulation ratings , maybe it's an all-round problem , not just limited to how I'm intending on using the toroids

316a