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24vac primary isolation transformer

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walter v

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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
 

MaxHeadRoom78

Well-Known Member
Most Helpful Member
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

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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

Super Moderator
Most Helpful Member
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

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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

New Member
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

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

JimB

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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

New Member
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

Well-Known Member
Most Helpful Member
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.
 

MaxHeadRoom78

Well-Known Member
Most Helpful Member
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.
 
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