220V Motor Test Rig - Page 1
Forum section: electronics / beginners

author: Dumpsterholic
author_rank: Regular Contributor
timestamp: February 11, 2019, 02:49:10 pm
content: Hi all.I recently salvaged some parts from a dust collection system. After some hassle, I was able to isolate the hefty motor from the squirrel cage, and now I want to test it. I know that some motors like this one can be switched from 220 to 110 operation by means of jumpers on the motor, but this one doesn't have that, so it looks like I'm stuck with 220. Discussions here and elsewhere have convinced me that trying to power it with standard American 110V is not a good idea, even though it might work for awhile. Some have suggested using a VFD, which I don't have; I'm wondering if the answer isn't staring me in the face in the form of an outlet in my house that appears to be wired for 220.Attached are some pics showing the motor and the outlet in question. If the outlet is wired correctly for 220, I should have two hots and a neutral, meaning that a volt meter connected between neutral and hot #1 should give a reading of 110V, and similarly, a meter connected between neutral and hot #2 should give the same reading; to power my motor I'd need the round plug to connect to neutral, and the other two plugs each to receive 110, adding up to 220. Have I got this more or less right?

author: rstofer
author_rank: Super Contributor
timestamp: February 11, 2019, 02:59:11 pm
content: Some houses have 220V dryer outlets (30 Amp?) and some have stove outlets (50 Amp?). As well, there may be a circuit for the HVAC condensing unit. Those are likely the only 220V outlets you have. Can you add a 2 pole breaker to the main panel or some sub panel?That looks like a sizable motor, 2 HP? More? You will want to have it bolted down when you turn on the power. The starting torque will be considerable.

author: Dumpsterholic
author_rank: Regular Contributor
timestamp: February 11, 2019, 03:09:09 pm
content: rstofer:Thanks! Yeah, it's a monster; 3hp according to the label. My other pics failed to upload, so here's another, and a look at the outlet:Don't know why the motor plate is upside down; honestly I'm in a lot of pain right now because I threw my back out. Maybe I shoulda left that critter in the Dumpster where I found it...Anyways: My question is really how to go about testing a 220V outlet. I have a meter that supposedly is rated for 600V; can I just jam my leads willy-nilly into pairs of sockets until I get a reading of 220?

author: rstofer
author_rank: Super Contributor
timestamp: February 11, 2019, 03:46:50 pm
content: I think that is a 20A 125V receptacle 5-20Rhttps://www.platt.com/platt-electric-supply/Receptacles-Commercial-20-Amp-Single/Leviton/5801-I/product.aspx?zpid=35200

author: Bratster
author_rank: Frequent Contributor
timestamp: February 11, 2019, 06:10:10 pm
content: Yep, that is definitely a 120 volt outlet.Go look at your breaker panel and see if there are any double pole breakers in it, that would tell you if you even have any 240-volt circuits in your house.If you have an electric dryer outlet, as was suggested above that is the best way to go.It's what I do at home, since I have a gas dryer I just leave a big extension cord plugged into the dryer outlet for me to run my welder and whatever a 240 volt devices I have.Sent from my Fi Moto x4 using Tapatalk

author: Fludo
author_rank: Regular Contributor
timestamp: February 11, 2019, 06:17:14 pm
content: Here's a typical AC power distribution diagram from split phase powerI wouldn't recommend measuring an outlet with an unknown voltage with "supposedly rated meter" stick to something name brand with appropriate CAT rating.Line-ground will be 120VACLine-line will be 240VAC3 wire 220VAC systems don't use a neutral as a return, but they have a safety ground which is bonded to neutral in at the sub-panel. 4 wire 220VAC outlets for dryers have a neutral connection to allow the use of 120VAC and 220VAC.The outlet you photographed is a 120VAC and won't work with this motor. It will not work with a VFD either because the 120VAC 20A recpetacle would provide ~2400W maximum, and the motor requires ~3300W.

author: Dumpsterholic
author_rank: Regular Contributor
timestamp: February 11, 2019, 06:54:45 pm
content: Thanks Bratster, Fludo and rstofer!So, I got up the nerve to measure the outlet voltage before I checked your responses. Yep. 120V was all I got.Finding 220V power may involve leaving the house, and that ain't gonna happen anytime soon. In the meantime, let me probe a little deeper into what this motor "wants" in order to function optimally. Seems to me that a 15A 220V circuit could safely power this; in the photo below can be seen two red wires with wire nuts on them. This is where the power comes into the motor from the big safety switch (not shown).Assuming the run and start capacitors (and centrifugal clutch etc.) are OK, all's I gotta do is reconnect the power cord, find a proper outlet, and plug 'er in. With no load attached, it'll (hopefully) spin along cheerfully without even coming close top drawing its (and the circuit's) rated 15 amps. No smoke, melted insulation, flesh-searing sparks... Right?

author: rstofer
author_rank: Super Contributor
timestamp: February 11, 2019, 10:57:10 pm
content: Quote from: Dumpsterholic on February 11, 2019, 06:54:45 pmYou are overlooking at least 90A of inrush current to get the motor turning. Technically, a decent 15A breaker might hold but a 20A would be the minimum I would use.20A breaker #12 AWG wireThere is also a requirement that the breaker be 25% larger than full load current because it will be derated to 80% of rated ampacity for long time loads. Always round up!

author: Dumpsterholic
author_rank: Regular Contributor
timestamp: February 12, 2019, 01:26:19 am
content: Of course, I suspected there was a factor I hadn't considered--inrush current. Meaning, even if I did find a dryer outlet in somebody's house, it might power up the motor, but it might immediately trip the panel, making me look like a doofus.Maybe, since I don't currently have a truck, I can load it onto my bike trailer and drag it to the nearest laundromat. There, I could wheel in my trailer, surreptitiously unplug a big dryer, and plug in my motor. Making me look like a doofus and a criminal.Nah. I have been planning a cross-country move for some time now; and once I tie up a few more loose ends I'm outta here. This motor is just another item in my pile. But when I look at that big fat impeller and heavy-gauge squirrel cage, I can't help but wonder if it's finally time to think seriously about building that backyard forge.