110V transformers: another question

[xerxes]

I've been reading the recent discussions on transformers with interest, and have some questions of my own.

I have a Wolf 5-speed bench drill designed for 50 volts which I would like to recommission (it's the Wolf of yesteryear, not the stuff advertised in the weekend newspapers these days). It has occurred to me to use a spare 110v site transformer for this.

I assume that I can connect between the centre pin and one of the side pins (I'm not sure of the correct terminology to use in this case) but does it matter which side? Would it affect the direction of rotation of the drill? Can I use a changeover switch to get forward and reverse?

And do I need to provide a fuse between the transformer and the drill?

Sorry if these questions reveal my ignorance: that's why I'm trying to be better informed.

 

[ban-all-sheds]

I assume that I can connect between the centre pin and one of the side pins

Yup - that will give you a nominal 55V AC.

It is an AC drill, is it? How come it's 50V?

(I'm not sure of the correct terminology to use in this case) but does it matter which side?

No.

Would it affect the direction of rotation of the drill?

No - it's AC so it makes no difference.

Can I use a changeover switch to get forward and reverse?

No.

And do I need to provide a fuse between the transformer and the drill?

Probably not a bad idea.


Does the drill have an earth connection?

 

[xerxes]

Thank you, Ban, for getting back to me.

It's not Wolf but Bridges (my memory is going). The plate says it's AC/DC, 50 cycles and 50 volts, 9 amps and 300 watts (is the last figure the output?)

It's got a 2-core 2.5mm flex coming out of it, insulation coloured black on both conductors. As it's all metal construction I assume it's not double-insulated. Do I need to provide an earth?

As to why it's 50 volts, your guess is as good as mine. For use in a special location? For a particular market?

I remember using one just like this on my first holiday job, to drill holes in steel sockets installed in concrete beams. No drill vice was provided, so when the twist bit picked up the workpiece I just had to cope with the problem. When the only bit was too blunt to drill, I had to go and find the office clerk to regrind it for me. They were happy days ...

 

[ericmark]

Bridges followed wolf in marketing a kit to go with the drill to do all sorts of extras wood turning etc. When Bridges went to the wall Black and Decker arrived and they cornered the market as their add ons were so cheap.
But the Bridges was a better made drill and I think they were used with a mag mount which may explain the voltage!

I would not think the 5 volt over voltage would really matter but I would fuse the drill and although using the one item off a single transformer may be OK if any other 110 volt stuff used the same transformer it could easy overload the transformer.

At 9 amp it needs a 1Kva transformer or it will overload the winding.

 

[Taylortwocities]

50volts DC is usual in telephone systems so the drill may have been used in that environment...?

Although I don't remember being allowed to connect anything other than telephone apparatus across the exchange batteries!

 

[Lectrician]

50volts DC is usual in telephone systems so the drill may have been used in that environment...?

Although I don't remember being allowed to connect anything other than telephone apparatus across the exchange batteries!

Thats a bit of a random suggestion!

You would never drag 9amps from a phone line! If you could, everyone would be using it for free lecky! The line will shut down when too much current is drawn.




I would warn that the center tap is EARTHED, and you should remove this connection ideally to give you a truley seperated 55v.

 

[Taylortwocities]

Lekky, I was making that observation from the viewpoint of someone working in the CO (telephone exchange). Should have clarified it.

I think the local loop is limited to 20mA - can't remember that far back and my Telephony Principles books are now pulped, somewhere!

 

[xerxes]

Thanks for the replies and the advice, everyone.

 

[Lectrician]

Lekky, I was making that observation from the viewpoint of someone working in the CO (telephone exchange). Should have clarified it.

I think the local loop is limited to 20mA - can't remember that far back and my Telephony Principles books are now pulped, somewhere!

Yep, rather suprisingly there is actually the potential for many thousands of amps in the larger telephone exchanges!