View Full Version : B&S #2 Universal 110V transformer question

02-13-2005, 03:52 PM
i was going over the wiring for the old B&S #2 Universal mill and there is a transformer to supply 110V to the starter coils. right now the machine is wired for 440V, and i need to convert it to 220V. the transformer has 8 wires labeled 1H, 2H, 3H, 4H, 5H, 1X, 2X and 3X. two of the H wires and two of the X wires are connected. does anyone know how the wires should be changed to switch the transformer to 220V?


andy b.

02-13-2005, 04:21 PM
Your Primary input (H's) need to be swapped parallel coils. Secondary side stays the same.

BUT, there should be only 4 H taps. SO I am confused there. I ain't gonna say yet so "we" don't make a mistake.

Can you post a picture?

02-13-2005, 10:59 PM

thanks for the reply. this is one case where i don't have easy access to a pic. the transformer is still in the mill, and one of the screws is behind the casting. to get it out i need to remove the entire panel (not THAT much work, but i'd prefer to avoid it).

anyway, here is how it is wired. there are eight leads as i mentioned (H1-5 and X1-3). they come out the bottom of the transformer in two rows of four.

H1 is capped off
X2 is capped off

H4 and H3 are tied together

X1 and X3 go to the 110V system (start switch and starter coils)

H2 and H5 go to two of the 440V legs

any ideas? i'm going to call B&S (well, Dev-whatever-their-name-is) tomorrow and see if the tech guy has any suggestions. sometimes they can help. otherwise i may just pull the transformer and connect it to 220V and see which connection schemes give me 110V on the secondary. the manual hints at some sort of parallel arrangement, but doesn't give any wiring tips.

andy b.

02-13-2005, 11:10 PM
Well, you have two coils in there, You series them to raise the resistance for the 480.. Parallel them for the 220 primary.

Seems 1,3 is one set, 2,4 the other.. but what throwes me off is the h5..

It'll take a meter or some kind of ohm device to check to see which coils is which.

The H - series middle tap comes out, parallel the two sets of coils, I'd dissconnect the output secondary till I checked voltage too.

2-4 is one set I bet, 3-5 is the other set. But I am not there with my meter to confirm so you have to before you apply power. If so, 2,3 to one leg, 4,5 to the other.. but like I said I'd check with a meter first.

You did change the motor over already? it should have internal taps also.
Normal 9 lead motor? then.. open up the connection box on the motor.
456 together, 1,7 line 1.. 2,8 line 2.. 3,9 line 3.. okay? swap any two leg sets to reverse. I always do that on the contactor.

I hate giving "blind" advice.. If it's right send a six pack of beer.. if it's wrong, oops sorry.. Make sure the transformer is fused.. okay?

02-14-2005, 11:21 AM
thanks for the info. i'll use a meter to check the resistances when i get home tonight. don't worry, i won't power anything up until i verify voltages.

and yes, i need to rewire all the motors for 220V. i'm getting to be a real expert at that.

andy b.

02-14-2005, 09:03 PM

here's what i got. i disconnected the transformer from everything and disconnected H4 and H3 from each other.

H1 was originally a no-connect
X2 was originally a no-connect
H3 and H4 were originally tied together (i disconnected them for my resistance measurements)
H5 and H2 went to two legs of the 440V 3ph supply for the transformer primary
X3 and X1 were the 110V outputs from the transformer secondary

i checked the resistances between the leads and this is what i got:

H5-H2 - open
H5-H4 - 9 Ohms
H2-H4 - open
H2-H3 - 8.5 Ohms
H5-H3 - open

H1-H3 - 12.6 Ohms
H1-H4 - open
H1-H5 - open
H1-H2 - 4.1 Ohms

X1-X3 - 7.4 Ohms

i then connected my supply from a standard 220/240V wall outlet (not the RPC) to the following leads and measured the output of the secondary across X1 and X3:

240V connected to H2-H3 -> X1-X3 measured 130V
240V connected to H4-H5 -> X1-X3 measured 130V

it looks like i can use either H2-H3 or H4-H5 and get 130V on X1-X3. does 130V seem alright or is that too high? i didn't check anything from X2, but i'm not sure what other voltage it would be set up to supply.

i still didn't wire anything up or turn on the "real" power. any thoughts?

andy b.

02-14-2005, 10:58 PM
Adding in the extra coils, will not add voltage. Just more current transfer.

Sounds like you hit the secondary hookup. If you just power up one half the primary you will achieve half the "true" current potential of the transformer.

Does this make sense to you? The polarity matters, if you hook it up reverse polarity the coils probably will cancel each other out and blow a fuse.
Sometimes there is a red dot showing polarity on transformers and stepper motors denoting magnetic polarity. I know this is true on most CUrrent transformers also since I have wired numerous current transformers into relays for phase loss in switchgear.

130 volts is fine, within the 15% range and you are mostly just using (powering) the coils in the starters correct?

MY RPC is buzzing the contactor and sticking. I think I am losing a relay and/or contacts in the starter. I built it out of used equipment.

If you take a neutral into your machine, you can do away with the transformer and use one leg of the 220. Make it a 4 wire to the RPC. Fuse it appropriately.

02-15-2005, 07:15 AM
hmmmm. now you gave me yet another question.

should i wire up BOTH the H2-H3 and H4-H5 coils? or will one of them give me the current i need? i guess it really is no trouble to wire them both up. i am guessing (a dangerous thing) that if i wire both coils up, that H2 and H4 should be connected to one leg, and H3 and H5 should be connected to the second leg.

i'm guessing the transformer is wound sort of like this (i hope my ASCII drawing works):


i would definitely go with the option to pull a neutral in and just use half the 220V, but the only wires going to the mill are the four from the RPC (three power lines and one ground).

oh, yes, this is only for the starter coils (there is an otion for a 110V light, but it isn't installed).

andy b.

02-15-2005, 09:46 AM
Then my "friend" plugged a drill motor into my computer quad plug on my milling machine.

For some reason that blowed the 5 amp fuse.

He said he knowed with them 4 receptacles there he had plenty of power.

Parallel the coils on the transformer, I don think they have seperate armatures, They are all wound around the same hunk of iron. Something to think about? the unpowered coils have electrical power on them if they are not grounded. HA.. let that soak in. And grounding them will "short the generated load out" so.. only ground the X0 or X2 neutral. If you don't you can ground either side and no effecto. Code says you need to ground the neutral thou.

Generated voltages in unused coils can knock you on your butt. I was working in a panel and looked, yep. there came a drop cord in a hole, they had "burned" out the control transformer, wired in a drop cord, yep.. old school they had put a light bulb in series with the circuit. When the current is drawing or flowing it lights the bulb. Yep, someone had came along and replaced the transformer, yep, even with the "visible 480 switch" off it knocked the "heck-outa-me" (4am.) The control transformer was generating 480 from the 120 supplied in the drop cord back into the 480 circuits.
I charged them from the time they woke me up till the time I went back to sleep.

I hate maintenance electricians. They will "kill" you. Starters hooked up with the power coming in the bottom, naked untaped wires, and there are thousands of "hot" 277 rotten rubber sj cords that used to go to lights hanging in the ceilings just waiting. After they mess a machine up so bad it can't be fixed in "normal time" they call in a expert.
Of course it is all discovery on "what all they did first" you have to repair the "fix (es)" before you can repair what actually happened to the machine. If it won't run you evidently start swapping wires.. (maintenance logic)


02-15-2005, 02:22 PM
i won't have a chance to do more wiring tonight, but i'll verify it tomorrow. if you don't hear back it either means it is working or i'm still laying on the floor next to the mill.

i also worked maintenance for a while for a large bakery. i loved when we'd power off the machines and the PLC controls, yet half the circuits would still be hot. all i did was fix what they said was broken and then would get the heck out of there. one i loved was where all the E-stop switches were wired together. yup, if you pushed one, all the SWITCHES would lose power. the machine kept running, but those E-stops were good and dead.

andy b.

02-15-2005, 03:32 PM
E-Engineers about E-stops should be horsewhipped and educated.

I have been on several bloody jobs because "they" tied a Normally open estop contact into a PLC input. But they save inputs? and they can parallel a hundred buttons they say.

BUT if the button/wire/contacts fails you stand there punching a button that does nothing. SERIES E-stop circuits ending in a E-stop relay is the only way something is safe.

(I have been ran off several jobs for Loudly telling engineers this) I should just run the stinking conduit and take my pay and go home. If there ever is bones, blood and a terrible accident do you know what they say? Wiring error.. not a engineering error.
And then, they poke multiple 500 mcm connections into a 12" square box. Sure it worked on the computer drawing.


02-15-2005, 04:48 PM
I went through this same thing recently when I converted my Sheldon from 440v to 220v. I posted these proceedures on Third Hand. Do a search with "220 conversion" in the subject and "viking" as the username and it will bring it up.

02-15-2005, 10:20 PM
thanks again to David, and thanks for the tip on your post, viking. it looks like all of us are in pretty good agreement (although i forgot about the starter heater switcheroo). i'll get a chance to wire everything up tomorrow and see if i need to order heaters. the main motor starter has been switched to an A-B, but the other two motor starters are still 1940s vintage B&S. we shall see what happens.

andy b.