Transformer 110v not working. Can I check if fixable before buying a new one?

[Jonny Vee]

how about a photo of the inside?

 

[Jonny Vee]

I`m just worried that I broke my expensive hammer drill with that voltage

If anyone have any idea on how the transformer is behaving like that would be appreciated.

Thanks

 

[Jonny Vee]

how about a photo of the inside?

Uploaded. Thanks

 

[SFK]

Only therotical method I can think of is a reduction in number of coils on Primary Side. This would in theory increase voltage on secondary side.

No idea how that would could come about though.

How were your resistance tests? Is there isolation between primary (input) and secondary (output)? ie there should be infinite resistance.

Sfk

 

[Jonny Vee]

Only therotical method I can think of is a reduction in number of coils on Primary Side. This would in theory increase voltage on secondary side.

No idea how that would could come about though.

How were your resistance tests? Is there isolation between primary (input) and secondary (output)? ie there should be infinite resistance.

Sfk

This is my multimeter. Apologize for the stupid question but I only know how to measure voltage. What I have to select on this?

 

[SFK]

Great to see that you have a Cat III meter. That is good.

Resistance is three clicks to right.
Text in white with Ohms sysmbol (bit like a curly 'n'). Test leads go in COM and the right socket that says V and ohms.

Looks like same setting is also a continuity test in that it will beep if resistance is zero.

(Also a diode test, but this not important to you).


To get hang of it in advance, put on resistance.

Touch test leads together. Should beep and display say zero, or 1 or 3 Ohms. This is low reaitance and is what you should see between live and neutral on motors and transformer coils.

On transformer Touch one probe on live on input side (plug) and then on all three pins of output side (socket) and display should show infinite resistance to show no connection. Repeat with neutral pin in plug and all three holes of output side (socket). Again should show infinite resistance.

Touch probes on earth of plug and of socket and should show connection between two with beep and very low/zero resistance on screen.


Sfk

 

[Jonny Vee]

Great to see that you have a Cat III meter. That is good.

Resistance is three clicks to right.
Text in white with Ohms sysmbol (bit like a curly 'n'). Test leads go in COM and the right socket that says V and ohms.

Looks like same setting is also a continuity test in that it will beep if resistance is zero.

(Also a diode test, but this not important to you).


To get hang of it in advance, put on resistance.

Touch test leads together. Should beep and display say zero, or 1 or 3 Ohms. This is low reaitance and is what you should see between live and neutral on motors and transformer coils.

On transformer Touch one probe on live on input side (plug) and then on all three pins of output side (socket) and display should show infinite resistance to show no connection. Repeat with neutral pin in plug and all three holes of output side (socket). Again should show infinite resistance.

Touch probes on earth of plug and of socket and should show connection between two with beep and very low/zero resistance on screen.


Sfk

Alright

Found it. Touching lead together can hear the bip reading 000.0

Touching L or N on side plug and all 3 pins of the three socket NO bip with meter showing OL

Touching probes on earth of plug and earth of three sockets yes can hear the bip reading 000.3

My question is why this toy is giving me 145v and still not sure if have already burnet my bosch hammer drill

 

[Jonny Vee]

How Do I check insulation resistance as per the attached youtube video on the first page at 17.50m.

https://www.youtube.com/watch?time_continue=1074&v=2t_JR0CxctQ&feature=emb_logo

Thanks

 

[SFK]

So I have no idea why you are getting high voltage. It might be because you are testing with no load (ie drill not connected) but I do not think this is the case. I remain worried that there is a short that has caused a reduction in number of coils on Primary Side that would in theory increase voltage on secondary side. And you cannot test for this as it is a v low resistance that has got lower.


Regarding the insulation test shown in video,
your test of:
Touching L or N on side plug and all 3 pins of the three socket NO bip with meter showing OL,
is a limited insulation test and shows no issues at 'zero volts'. BUT there might be an issue of wires touching only at mains voltage.

To do the isolation test shown in video you need special test kit to do that test (it puts in 500V which is more likely to 'jump' poorly insulated wires/tracks on one side and sees if you can see any voltage whatsoever on other). That test kit is not that cheap so might be better to now get new transformer.

Sorry

 

[Jonny Vee]

So I have no idea why you are getting high voltage. It might be because you are testing with no load (ie drill not connected) but I do not think this is the case.

Regarding the resistance test shown in video,
your test of:
Touching L or N on side plug and all 3 pins of the three socket NO bip with meter showing OL,
is a an insulation test and shows no issues at zero volts. BUT there might be an issue of wires touching at mains voltage.

To do the test shown in video you need special test kit to do that test (it puts in 500V on one side and sees if you can see any voltage whatsoever on other). That test kit is not that cheap so might be better to get new transformer.

Sorry

Because I don't have another transformer I have no idea if the actual voltage is higher than it should be. It's strange and on a very simple kit of equipment like that don't understand what's wrong.

I'm sure someone has an answer to that.

Thanks for your help

 

[Jackrae]

Does your meter have a "peak-to-peak" measuring mode. Your measured 145v might suggest so. Can I suggest (as a very crude calibration comparison) you use the same meter to measure your house mains supply and advise what it reads. Also on one of the LV-side sockets measure each of the output lines relative to the central earth pin - they should each read 55 volts.

 

[ericmark]

OK it is an isolation transformer, rated 2 kVA with a 5 kVA peak, there should be no way it can give the voltage you have measured, I can't explain why it did, the OL on the meter means over load, in real terms it means can't measure as out of range. The little device with the brown wire with blue spade connector and the black wire with yellow spade connector are fitted to an overload and the meter should show around 000.3 same as when you tested earth wire when testing the overload.

The

review for the meter is not good, so it may be the meter faulty not the transformer. The same dial position give diode test and resistance could not see how you select, one measures ohms the other threshold volts clearly you want ohms range.

 

[SFK]

Eric, for this meter i presumed the diode test was a basic direction of diode test, and does not provide a diode threshold measurement.

Your Mains voltage test is a good idea to get basic calibration and also see if the meters 'True RMS' AC versus DC measurement differentiation is working.
SFK

 

[Jonny Vee]

Each read is 74v on the outlet socket of the transformer. I have also tested the house socket and the reading is 240v

 

[Jackrae]

OK looks like you've got a sh1te el-cheapo transformer that puts out 110v only when fully loaded. ie extremely poor regulation. As I've said many times before "A CE mark means bu**er all" when it comes to quality. Alternatively, one could suggest that the transformer reduction ratio (nominally 2:1) has decreased due to a shortened primary turn, or turns, the effect of which would be to increase the secondary voltage. But this would also greatly increase the primary current (transformers just love shortened turns). And now we might be zeroing in on why the unit tripped out in the first place.