24vac primary isolation transformer

[walter v]

i need to find 24 vac isolation transformers. the max load i need is 0.5 A. ideally a 12 vac secondary but 24 vac will work.
if not, can i use an 110 v 1:1 transformer and run it with 24 V? but size is an issue, do they come in 12 vac?
thanks a lot ............. walter

 

[dknguyen]

I don't see why not.

 

[MaxHeadRoom78]

Pick up a small 20va Toroidal transformer and use the 24v winding as the primary, or remove turns to suit.
Wind on a small overwind of about 24T for 12v.
Seal off the mains input connections.
Ebay 263275635325 e.g.
Max.

 

[Diver300]

If you don't exceed the current rating, you can use a transformer at a lower voltage.

If you have a 30 VA 110 V primary 55V secondary transformer that can supply 0.5 A, so it will be fine converting 24 V to 12 V and supplying 0.5 A.

It will be much larger than if you got a transformer wound specially.

How many do you need? Is this to run at 50 /60 Hz or is it some other frequency?

 

[JimB]

Or, use two transformers.

Transformer #1 24v to 110v

Transformer #2 110v to 24v or 12v as you require.

Wind on a small overwind of about 24T for 12v.

I like the idea of adding your own winding, but, 2 turns per volt sounds a bit optimistic.
For a small transformer I would expect 5 or 6 turns per volt, so you would need 60 or 70 turns to give 12v.

JimB

 

[MaxHeadRoom78]

I like the idea of adding your own winding, but, 2 turns per volt sounds a bit optimistic.
For a small transformer I would expect 5 or 6 turns per volt, so you would need 60 or 70 turns to give 12v.

JimB

I have rewound and also added overwinds on many different transformers over the years, the EI type I found was up around the 5t/volt, but Toroidal I have found as low as 1.5t/v
For a small one it could be higher, I have one here I can test.
But it is usually simple with a toroid to put on a few temporary turns and measure to find exactly.
Max.

 

[walter v]

If you don't exceed the current rating, you can use a transformer at a lower voltage.

If you have a 30 VA 110 V primary 55V secondary transformer that can supply 0.5 A, so it will be fine converting 24 V to 12 V and supplying 0.5 A.

It will be much larger than if you got a transformer wound specially.

How many do you need? Is this to run at 50 /60 Hz or is it some other frequency?

thanks,
hopefully i will need a few hundred, all 60 hz. any idea who sells miniature 20-30 VA transformers in Canada or US?
thanks again .......... walter

 

[MaxHeadRoom78]

There is Hammond, but for custom toroidal type, there is AnTek he builds toroidal to order .
Max.

 

[JimB]

hopefully i will need a few hundred

In that case, it would be a good idea to talk to a transformer winding company rather that implement our one-off hobbyist prototype work arounds.

JimB

 

[walter v]

thanks,
hopefully i will need a few hundred, all 60 hz. any idea who sells miniature 20-30 VA transformers in Canada or US?
thanks again .......... walter

 

[Diver300]

What exactly is the application?

If you want it to be as small as possible you will need something made specially. It's not technically difficult, to make a transformer, but all the mass-produced ones have 120 / 230 V inputs, so any standard transformer will have a primary winding that you don't want, so it won't be as small as it could be.

 

[rjenkinsgb]

How about using a transformer that already has two separate 24V secondary windings - and just use one of those as the primary & the other as teh secondary?
(And of course insulate the original primary terminals).

eg.
https://uk.rs-online.com/web/p/chassis-mounting-transformers/0504329/
https://uk.rs-online.com/web/p/toroidal-transformers/1176056/

 

[MaxHeadRoom78]

Mostly what I said in post 3, if you have two winding's already then that should work.
AnTek offer
Bulk Discounts
Large quantities automatically qualify for discounts at checkout.
Might be worth getting a quote also.
Max.