Hi folks

Can I connect a (240V 50hz -> 24V AC) 120VA transformer to a circuit rated at 24V 3A 100VA and will there be any problems with overload if I do?

Stupid Question I know but this is my first ever play around with transformers.

Thanks for your help.

Craig

 

You have a transformer with a 240 VAC 50 Hz primary and a 24 VAC 50 Hz secondary which is a 120 VA transformer. That tells me it has a 24 VAC 5 Amp secondary. You want to run a load which is 24 VAC 50 Hz 3 Amp. That would be fine. I don't understand that last 100 VA you have? 24 Volts @ 3 Amps = 72 VA.

Ron

 

I have this transformer but I am a bit confused on the wiring instructions on it.
I want 24V on the secondary

I think this is right but I would like a second opinion;

JUMP B to F and secondary out is A and E


Thanks folks


Craig

 

You have a transformer with a 240 VAC 50 Hz primary and a 24 VAC 50 Hz secondary which is a 120 VA transformer. That tells me it has a 24 VAC 5 Amp secondary. You want to run a load which is 24 VAC 50 Hz 3 Amp. That would be fine. I don't understand that last 100 VA you have? 24 Volts @ 3 Amps = 72 VA.

Ron

Hi Ron; its an old japanese pachinko machine (pinball) and on the cover of the circuit board is written 24V AC 3A 100VA so I assumed this is what it requires - I'm new to electronics and still learning the formulas
Here is a pic of the cover

 

Yes move the green wire to E and that will give 24VAC.

(It's not good practice to use mains coloured wires or green/yellow earth wires for low voltage AC).

 

Yes move the green wire to E and that will give 24VAC.

(It's not good practice to use mains coloured wires or green/yellow earth wires for low voltage AC).

Thanks for the wire color tip; any suggestions on appropriate color?

 

You should be fine using the transformer you mentioned. Ah yes, fond memories of those pachinko machines. Generally when you see a power requirement like that it means the max power the circuit will draw. For single phase AC the VA is simply the Voltage * Current or Volts * Amps.

Ron

 

JUMP B to F and secondary out is A and E

That will do it.

Ron

 

You should be fine using the transformer you mentioned. Ah yes, fond memories of those pachinko machines. Generally when you see a power requirement like that it means the max power the circuit will draw. For single phase AC the VA is simply the Voltage * Current or Volts * Amps.

Ron

I tried this transformer on another pachinko rated the same and it blew out a 47V MOV so I'm reluctant to use it; Multimeter says its OK; any ideas on what may have caused this (the pachinko has been sitting for 24 years unused; but all circuitry looked fine when I checked it; looks like I'll be double checking it once I remove/replace the MOV and try again.

Here is a piccie of the transformer

And here is a picture of the pachinko for your nostalgia

thanks mate

Craig

 

I remember that. You had a thread on it. I haven't a clue why the MOV failed. There are components, some capacitors come to mind which over time will degrade but generally MOVs don't fail unless there is a major voltage spike or surge.

Ron

 

I remember that. You had a thread on it. I haven't a clue why the MOV failed. There are components, some capacitors come to mind which over time will degrade but generally MOVs don't fail unless there is a major voltage spike or surge.

Ron

Thanks for all your help Ron and everyone else I'll end this thread now. see ya

Craig

 

There is pretty much only one reason a MOV (VDR) fails is due to sustained voltage over and above the maximum rated, current increases as the voltage rises over the normal voltage operating point.
Max.