Question about proper xformer connections? (2024)

I have attached a picture of a transformer I have connected hopefully correctly. It is dual voltage 220/440 volt primary voltage, 110 volt secondary. There was no connection schmetic on the xformer. This is a common xformer that Lodge & Shilpey put on their lathes back in the 1950's. I think I have it wired for 220 volt as shown. Can someone tell me if I'm correct or not?

Thanks,

Ken S.

(For some reason, it won't let me attach a picture or link to the picture)

I have H1,H3 connected together, then H2,H4 connected together. Would this be correct for 220 volt?

Ken

Fairly good chance that is correct Ken, but see what the resistance is before you shoot the juice to it.

If open, it isn't right

If zero resistance, it isnt right.

I think the high voltage lash up is power to H1 and H4 with H2 and H3 jumpered together.

If some resistance and not open, give it a try and check output.

If it complains, turn it off.

I have one sitting here - I'll take a look at it today and see if it says anything.

John Oder

Thanks John,

I'll check the resistence on it next chance I get.

Ken

Safe way to check transformer connections

Get a little 12-volt door bell transformer from your local DIY store.

Connect its primary to 120 volts and its secondary to the primary of the transformer (DUT = device under test).

You can then measure the output voltage of the DUT, and see how it changes with various primary tap configurations. Under most conditions this voltage won't exceed about 50 volts, so it's not hazardous.

For your particular transformer, with 240/480 in and 120 out...
If your primary is strapped for 240, the output of the DUT in the test system will be 6 volts.
If your primary is strapped for 480, the output will be 3 volts.

Resistance measurements can also be used (transformer completely disconnected, obviously).
For a simple four-terminal dual-voltage primary, connection in the high-voltage configuration will give a resistance four times the value measured when strapped in the low-voltage configuration.

- Leigh

Ken - this little GE connects hots to H1 and H4 in either case. To get 115 out with 460 in you jumper H2 to H3. The get the same out put with 230 in, you jumper H1 to H3 and H2 to H4. Note they have them arranged so that is easy with the two jumper plates provided. Currently set up for 460 input. This came out of a '80 (or so) Series 2 NC BP

John Oder

minder said:

The trouble with a resistance test on a dual winding primary is that it is possible to hook it up out of phase which results in a dead short.

Click to expand...

True.

That's why I recommended the low-voltage test first. It's absolutely accurate and safe for virtually any unknown transformer.

I only mentioned the resistance test because a previous poster had mentioned it without any details as to the expected results.

- Leigh

A little late,

Here's the transformer in question.

Leigh, I'll try your recommended test, I have a door bell that is not being used right now and a push button.

Ken

You do not need to do that transformer test as mentioned.

Disconnect the H1 - H4 connections. Use a ohm meter and determine which
connections are associated with the two independent primary windings. Then
you just wire them in parallel (looks like you did this correctly). The phasing
has to be correct. If you have a data sheet then it is easy. The dot on the
connection picture for each coil will tell you the orientation. If not data sheet then:

Just disconnect all wires from the transformer. Connect the secondary to a
alternating source and scope the secondary lines. It will be easy to determine
how the coils are correctly phased.

From a few transformers I have the H1-H2 and H3-H4 are the two coils.
The phase orientations are odd numbers to odd numbers and even numbers
to even numbers. Looks like you did the right thing and all this is just academic,
but since this a older piece of iron the test I describe is a good check.

Thanks Ron and others,

I am going to hook up 120 volt AC to H3, H4 and check the secondary voltage and see if it is around 50 volts before putting on line.

Ken

rons said:

Ken, do you have a oscilloscope?

Click to expand...

No, I keep saying I'm going to buy one, but haven't.

Ken