# WW Machinery related electrical question

• posted on November 4, 2014, 8:24 pm
I found a tool that has a plug upon which it says: 30A 600VAC 30 250V Does that mean it is 3-phase?
Yes, I know I should be looking at a tag on the motor, but it is inaccessible at the moment.
Thanks, Bill
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• posted on November 4, 2014, 9:24 pm
On 11/04/2014 2:24 PM, Bill wrote:

...
Doesn't prove it, no, but at those amperages there'd be a good chance't it would be.
Better klew could be the plug configuration--number prongs, shape...
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• posted on November 4, 2014, 11:43 pm
dpb wrote:

It was one of those that you push in and twist. At the time, I thought what I wrote down above would tell the whole story. It's actually a machine from a high school.

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• posted on November 4, 2014, 9:29 pm

I'm guessing that the zero in the second "30" has a slash or vertical bar through it, in which case, yes, it's 3-phase. Look at this image, for example:
http://cds.a9t2h4q7.hwcdn.net/main/store/20090519001/items/media/Electrical/passseymo ur/ProductLarge/5760.jpg
You can also tell whether a plug or receptacle is single-phase or 3-phase, as well as its rated voltage and amperage, by comparing it to a NEMA plug configuration chart.
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• posted on November 5, 2014, 12:49 am
wrote:

Twist lock doesn't tell much. They come in all voltages and phases (generally at the higher currents).
You can match your plug to these charts:
Twist-lock: http://www.quail.com/locking_nema_chart.aspx
Normal: http://www.quail.com/nema_chart.aspx
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• posted on November 6, 2014, 2:07 am
On 11/4/2014 2:24 PM, Bill wrote:

This may well be a motor that is two voltages. Why the same current ? hum.
Going to have to look. Three phase is full of many many wires. At least six maybe four and maybe 12 or so.
A single phase will have two wires and an earth (maybe). Is it a big one a 30hp ? 1800 watts one way and 7500 the other.
Best look. and post a picture somewhere for all to see.
Martin
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<%-name%>
• posted on November 6, 2014, 2:40 am
Martin Eastburn wrote:

It was from an (old) Rockwell jointer, having an 8" by 5.5' bed,at an auction. Serial#: 124-6065 (in case that suggests a date or anything). It had a "heavy" power cord. Its location among other tools made it inaccessible. I could not open it's "power box" with my hands ; it may have been slightly smashed in. It was previously owned by a school district near Indianapolis. On a day with fewer conflicts, I would have tried harder to attend the auction if I knew it wasn't 3-phase. The available evidence seemed to suggest 3 phase.
Bill

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• posted on November 7, 2014, 12:55 am

That's a peculiar set of numbers to see on a plug.
I am going to guess here that the 250V is a DC rating (altho it is unusual to see that on a connector you occasionally will). So your motor is probably a 600V 3-phase motor. The second 30 (without an "A" after it) is probably an "O" with a slash thru it, indicating 3 phase.
John
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• posted on November 7, 2014, 1:51 am
John McCoy wrote:

Looking at the bottom of the connector, the "30A 600VAC" was centered accross the top, and the 30 250V was centered accross the bottom. I accept your analysis below as probably correct. Being an "industrial strength" 8" Rockwell jointer, the 3-phase feature makes sense.
Thanks! Bill

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• posted on November 7, 2014, 12:55 pm
"Martin Eastburn" wrote
For a large joiner, 2 or 3 phase is likely and likely wanted as well. 2 phase is real 3 phase with a missing leg. It isn't single phase 220.
********************** Watt?
2 phase is nothing. It makes a machine sit there and hum.
Normal residential 220, or 240, is single phase. Phase indicates how many lines have electricity in them with a sine waveform of voltage over time.
Three phase has three lines, and each have their own sine wave going that are 120 degrees out of sync with each other.
Residential 240 has one hot line coming to the transformer. It has one sine wave. The transformer is center tapped and the juice is sent down two hot lines to your house. It is the same sine wave that is now 180 degrees out of phase. Still single phase. Ground to either line is 120. Line to line is 240. Still single phase.
Then there is a mixed three phase, as was in my school. Three hots, three sine waves. We did not have single phase 240. If you were to tap from one hot line to another, you got 208 volts. Y tap, I think they called it. I don't recall what the 110 volt was from hot to ground. Around 113, I think.
Bad idea to run a motor intended for 240 on 208, when it is being used at close to its rated maximum load. Decreased voltage causes it to draw more amps, and more amps means hot and eventually burn out.
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• posted on November 8, 2014, 3:14 am
That is why milk producing dairies run 2 phase on their stuff - And the large saw mill that once had this land as it's own used two phase.
One uses 2 phase and generates a third automatically. Inverted V or open delta is the way it is done.
Martin
On 11/7/2014 6:55 AM, Morgans wrote:

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• posted on November 10, 2014, 3:04 pm

Surely not in a woodworking shop. Much more likely to be two-hots + grounding for single-phase, three-hots + grounding for 3-phase.
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• posted on November 10, 2014, 8:27 pm
email.me:

For combined 240V/120V loads, sure. For a pure 240V load? Doubtful. Can you cite examples where a perfectly useless neutral wire is required for a pure 240V load?

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• posted on November 10, 2014, 8:38 pm

Scott is correct with respect to 3-phase. 3 hots, possibly a ground. No neutral.
240 single phase is trickier - often in modern wiring there's a neutral, so you can use it as either two 120 circuits or one 240 circuit. I don't really like that, but it helps stop hacks from using one leg of the 240 and ground as a 120 circuit.
John
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• posted on November 10, 2014, 10:20 pm
Scott Lurndal wrote:

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"Mike Marlow" wrote:

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"John McCoy" wrote:

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What is being totally forgotten are the "Y" services.
480V/277V/3PH/4W/60HZ and 208V/120V/3PH/4W/60HZ.
Both require 3 "hots" (L1, L2, L3), neutral and ground.
I would expect any school or other light commerical (shopping centers, etc) buildings built in the last 40 years to be supplied with 208V/120V.
There are lots of reasons including lower cost and SAFETY.
Lew
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• posted on November 11, 2014, 4:19 am
On 11/10/2014 4:20 PM, Lew Hodgett wrote:

Right - military and police / hospital tend to have delta/delta transformers - allowing a leg in primary and/or secondary to be lost and continue to deliver 66% of the rated power. These need it all of the time customers over rate their transformers so the 60% is their real need.
Schools go on low budgets and save on copper runs of large wire.
You can bet that every machine is GROUNDED. So if Three phase its 4 or 5 wire.
In industry we used 1000 amp /leg - 3 phase - 5 wire ground and neutral from the box. Some local codes require 4 some 5 and the 5 was a super class that passed Europe as well. Those Hubble plugs were monsters. Most customers wired directly to the panel or overhead Buss Bars power box.
Martin
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• posted on November 11, 2014, 5:37 pm

I don't think you'd find a motor wired as a Y connection, tho. Motors are usually in the delta configuration (altho there some that start in a Y configuration and switch to delta to run, you still just see the 3 hot leads externally, there's no neutral connection).
John