TheBackShed.com

Forum Index : Electronics : USA source for split phase toroidal trans

Author

Message

rustyrotors
Newbie

Joined: 07/01/2023
Location: United States
Posts: 36

Posted: 12:43am 06 Feb 2023

Copy link to clipboard

Print this post

after searching high and low for affordable toroidal trans in the USA, i found potential source on ebay.. search for "voltage converter." you will find a few different variations of basically an autotransformer box for under $100, some are supposedly rated for 5000w and have a toroidal trans inside with two 115V windings in series. i ended up purchasing this one:

https://www.ebay.com/itm/124889104671

its not potted, all you have to do is add your secondary winding. this trans is roughly 180mm width x 100mm height. the windings measure 0.6 ohms in series, so the 5kw rating seems to be fairly accurate

Edited 2023-02-06 10:47 by rustyrotors

tinyt
Guru

Joined: 12/11/2017
Location: United States
Posts: 438

Posted: 04:05am 06 Feb 2023

Copy link to clipboard

Print this post

Good find!

I think it is an autotransformer, so for an isolation transformer application like in an inverter it will probably have to be rated at 2500 watts.

You will probably need to add more turns to the 110/220v windings to lower flux density and no load power draw.

If you add the mosfet drive winding, using multiple strands of small dia. magnet wires, one strand at a time will allow you to make the most use of available toroid hole space.

Edit: uploaded picture will not show, deleted
Edited 2023-02-06 14:22 by tinyt

phil99

Guru

Joined: 11/02/2018
Location: Australia
Posts: 2135

Posted: 05:33am 06 Feb 2023

Copy link to clipboard

Print this post

Quote I think it is an autotransformer, so for an isolation transformer application like in an inverter it will probably have to be rated at 2500 watts.

Exactly. For a 2:1 autotransformer only half the output VA is provided by the core, the rest comes from the input.

wiseguy

Guru

Joined: 21/06/2018
Location: Australia
Posts: 1156

Posted: 05:46am 06 Feb 2023

Copy link to clipboard

Print this post

TinyT is right the auto-transformer only needs to be capable of 2.5kW.
For 5kW of 230 the current required is 21.7A but at 115V it is 43.4A.
The input current has two 21.7A components one for the transformer primary and the other is added to the 21.7A 115V secondary so it adds to the input voltage to equal 230V (@21.7A).

The input supplies the whole 5KW the transformer transforms 115V @ 2.5kW.

I decided to sketch it to aid with the understanding, sorry but the graphics let me down the currents do not show the dash of the A and look more like an upside down V. The transformer is drawn like a conventional tranny but the result is the same as a centre tapped auto style winding.

Edited 2023-02-06 15:47 by wiseguy

If at first you dont succeed, I suggest you avoid sky diving....
Cheers Mike

rustyrotors
Newbie

Joined: 07/01/2023
Location: United States
Posts: 36

Posted: 12:41pm 06 Feb 2023

Copy link to clipboard

Print this post

ok i will keep it under 2.5kw on 115v. that makes sense for reasonable heat dissipation too, probably get a bit toasty at 5kw

my local grid runs a little hot at 125V, no load pulls about 10W. I will probably run it as is, im using it to build a backup inverter

rustyrotors
Newbie

Joined: 07/01/2023
Location: United States
Posts: 36

Posted: 10:34pm 06 Feb 2023

Copy link to clipboard

Print this post

it ended up taking 18 primary turns to make 115/230V from 15V, with cross section of 40cm2, that make just under 0.8 tesla if my maths correct
Edited 2023-02-08 09:18 by rustyrotors

get real
Newbie

Joined: 16/12/2020
Location: United States
Posts: 9

Posted: 05:48pm 05 May 2023

Copy link to clipboard

Print this post

you added 18 turns on top of coil? and put 15v in and got 115/230? is this right? thanks.

Print this page

To reply to this topic, you need to log in.