Hello. I had a few transformers from old electrical appliances. How to check what voltage and current the transformer gives?

Find on the net after the markings. Connect and measure the voltage. Knowing the core cross-section and the diameter of the winding wires, it is possible to estimate the approximate power of the transformer.

read what is written on it and look for information on this topic. in the absence, measure the resistance of the windings and where it is the highest, and you can see that this winding is more isolated from the others, it can be a 230V winding, then you can connect it in series with a 25W / 230V bulb. If the bulb does not shine, it is probably 90% of the mains winding and you can connect directly to the mains and measure the rest of the windings. And only then can you Worse, if a transformer from tube devices is, the anode winding may have the highest resistance, or a speaker transformer.

Well, you are right, but I bet that when the author asks the current and voltage of the transformer, he knows where he got them from and knows their purpose. And it doesn't have to be that way ... Well, I even assumed that he knows where the primary and where the secondary winding / windings were.

I took out 2 transformers from old printers. I do not know the printer models, because the housings were thrown away some time ago.

I measured the transformer resistance on the side where it is connected to 230V. And it has 500. On the other side of the transformer (where a thin wire is wound) there was 0.7 ohms.

The 500 ? a bit strange. Too much resistance for me. You may have been wrong. It cannot be like that either. You write that where there is a thin wire there is only 0.7 ?. Such resistance is usually where the thick wire is wound, i.e. on the secondary.

500? is a reasonable resistance of the primary winding of a transformer with a power of about 5W. What is the core cross-section?

How to Check Transformer Voltage & Current: Identifying Output from Old Electrical Appliances

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#1 16886399 12 Dec 2017 20:21

mateusz2015_5102 mateusz2015_5102

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16886399 12 Dec 2017 20:21

Hello. I had a few transformers from old electrical appliances. How to check what voltage and current the transformer gives?
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#2 16886449 12 Dec 2017 20:35

Jawi_P Jawi_P

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16886449 12 Dec 2017 20:35

Find on the net after the markings.
Connect and measure the voltage.
Knowing the core cross-section and the diameter of the winding wires, it is possible to estimate the approximate power of the transformer.
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#3 16886474 12 Dec 2017 20:45

wada wada

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16886474 12 Dec 2017 20:45

read what is written on it and look for information on this topic.
in the absence, measure the resistance of the windings and where it is the highest, and you can see that this winding is more isolated from the others, it can be a 230V winding, then you can connect it in series with a 25W / 230V bulb.
If the bulb does not shine, it is probably 90% of the mains winding and you can connect directly to the mains and measure the rest of the windings.

And only then can you

Jawi_P wrote:

Knowing the core cross-section and the diameter of the winding wires, it is possible to estimate the approximate power of the transformer.

Worse, if a transformer from tube devices is, the anode winding may have the highest resistance, or a speaker transformer.

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#4 16886551 12 Dec 2017 21:07

Jawi_P Jawi_P

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16886551 12 Dec 2017 21:07

wada wrote:
Worse, if a transformer from tube devices is, the anode winding may have the highest resistance, or a speaker transformer.

Well, you are right, but I bet that when the author asks the current and voltage of the transformer, he knows where he got them from and knows their purpose. And it doesn't have to be that way ...
Well, I even assumed that he knows where the primary and where the secondary winding / windings were.
#5 16886856 12 Dec 2017 22:55

mateusz2015_5102 mateusz2015_5102

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16886856 12 Dec 2017 22:55

I took out 2 transformers from old printers. I do not know the printer models, because the housings were thrown away some time ago.
#6 16889223 14 Dec 2017 08:16

mateusz2015_5102 mateusz2015_5102

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16889223 14 Dec 2017 08:16

I measured the transformer resistance on the side where it is connected to 230V. And it has 500.
On the other side of the transformer (where a thin wire is wound) there was 0.7 ohms.
#7 16889336 14 Dec 2017 09:24

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16889336 14 Dec 2017 09:24

The 500 ? a bit strange. Too much resistance for me. You may have been wrong.

mateusz2015_5102 wrote:
.
On the other side of the transformer (where a thin wire is wound) there was 0.7 ohms.

It cannot be like that either. You write that where there is a thin wire there is only 0.7 ?. Such resistance is usually where the thick wire is wound, i.e. on the secondary.
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#8 16891176 14 Dec 2017 23:46

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16891176 14 Dec 2017 23:46

500? is a reasonable resistance of the primary winding of a transformer with a power of about 5W. What is the core cross-section?
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Topic summary

✨ To check the voltage and current output of transformers from old electrical appliances, users are advised to examine any markings on the transformers and measure the voltage directly. If markings are absent, measuring the resistance of the windings can help identify the primary and secondary windings. A higher resistance winding may indicate a 230V winding, which can be tested by connecting it in series with a bulb. If the bulb does not light, the winding is likely for mains voltage. Users should be cautious with transformers from tube devices, as the anode winding may have the highest resistance. One user reported measuring 500 ohms on the primary side and 0.7 ohms on the secondary, prompting discussions about the expected resistance values for transformers of different power ratings.
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How to Check Transformer Voltage & Current: Identifying Output from Old Electrical Appliances

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