View Full Version : Electric motor wiring ?
12-17-2008, 10:38 AM
My father-in-law has a machine in his shop that runs off an electric motor . There is a plate on the motor that has diagrams that shows how to wire the motor for 120 v or 240 v . The motor has 4 wires coming out that are numbered 1-2-3-4 . For the 240 v connection it shows 2&3 together & 1 & 4 connecting to L 1 & L2 . That's the way it was wired when he got it , however he hooked it up to 120 v & it ran . For the 120 v connection it shows 1&2 connected to L 1 & 3&4 connected to L 2 . Since he wanted to run it on 120 I switched the motor wiring to match the 120 v diagram . It wouldn't run so I switched it back . It was getting late in the evening so I didn't check amperage , rpm , ect . I haven't been back to do any further checking so you now know as much as I do . Ideas , opinions ????
12-17-2008, 11:25 PM
If my memorey serve me right you need to hook 1,3 to L1 and 2,4 to L2 that for 120 volts connections
before you do anything more do you know what motor manufacter it is ?
I pretty sure this is one of older motor style which I haven't see it for while.
12-18-2008, 05:06 AM
Your post does not make sense. You said that it worked when wired for 120v then switched it to 120v and it would not work. Do you mean you tried it at 240v?
You will have to change your breaker and the setup in the breaker panel when you change from 120 to 240.
12-18-2008, 07:37 AM
No didn't try it at 240 . This machine is one my father-in-law just got . I was at his house for a different reason & didn't spend much time fooling with the machine . Where he placed the machine in his shop is right beside a 120 v receptacle . It pulls 13.6 amps wired for 120 . There is a 3 wire cord to connect to line voltage . One wire is a ground & the other 2 go into the motor through a fused on / off switch . He stuck the two motor wires in this cord into the power & neutral slots on the 120 v receptacle & the motor ran but the diagram on the motor showed it was wired for 240 v . I'm wondering why it didn't run when I switched the wires on the motor to match the 120 v diagram .
12-18-2008, 05:48 PM
The motor has two windings, each of which is made to operate at 120v. Connecting 2&3 together puts the windings in series, which means that if you apply 240 volts each winding gets 120v. When you connect 1&3 and 2&4 together the windings are in parallel, and they need 120v applied. This is what Marc was saying in his post. I suspect that you may have misread the wiring diagram, and would suggest that you take a closer look at it when you get a chance. Here's a crude drawing that I slapped together that should help to explain how this works.
12-19-2008, 09:00 AM
Thanks , makes perfectly good sence . The machine & motor are pretty old & the diagram was pretty hard to read so I probably misread it . The motor wires have metal clamps around them with numbers stamped in the clamps so they are not hard to read . Would a motor such as this likely run on 120 if it's wired for 240 at the motor ? I realize if the answer is yes the motor likely wouldn't be running properly .
12-19-2008, 09:23 AM
It depends mostly on the load. If the load was light enough that the motor could get running and up to speed in a short time, then yes, it would run.