110 v 3 phase motor
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  1. #1
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    Default 110 v 3 phase motor

    I purchased a B&S #2 surface grinder and a few other machines from a facility that was closed down and the person liquidating the stuff really had no idea about anything which worked out well for me price wise. The grinder was hard wired and I had to disconnect it from live power. It was a 4 wire connection so it was simple to clip and cap the leads one at a time. I never checked the voltage and just assumed it was 230v 3 phase with ground wire as it came up from a pipe in the floor and no transformers anywhere in site.

    I started to clean up the grinder and wiped down the spindle motor. The nameplate reads 110V 60 hz 1 hp but the phase info is damaged and unreadable. I opened the motor cover and count 3 wires feeding into the motor which leads me to believe its 3 phase single voltage. No capacitor on this motor.

    There is a second motor inside the cabinet for the table but I could not see the plate without a small mirror and some poking around. I will try to tackle that next week

    My work place is 230 v 3 phase. I cant go back to the old place to verify what voltage the grinder was connected to or if there was a transformer in the electric path.

    I have never seen a 110v 3 phase and like to explore my options to run the machine. I don't think its practical to replace the motors.

    1) Will a static phase converter work with a 110 v input single phase and give me 3 phase output at 110V?

    2) Can I use a vfd like a teco and program the output voltage to be capped at 110v?

    3) Is there a transformer I can use to drop the voltage?

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    I'm not an expert, but I don't think that there's any such thing as 120V 3 phase on the US. I'm not sure why there are three wires- Hot, neutral, ground, perhaps? As you probably know, 3ph gets 240 volts from adding any two 120V legs. Many (most?) areas have a high leg, or stinger ranging from 208 to 240V. I dd a very brief google search, and couldn't find anything about 120V 3ph, but again, I'm not an expert.

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    I have seen 120v 3 phase motors before. Usually to get an advantage when running at 240V 120Hz (and double speed).etc.

    Pictures of the nameplate?

    Is any wire conneted to the case?

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    Quote Originally Posted by JST View Post
    I have seen 120v 3 phase motors before. Usually to get an advantage when running at 240V 120Hz (and double speed).etc.
    I even have a Weg VFD built for in/out 120 V 3-phase. ONLY. AND NOT step-up or step-down.

    The need is not common, but the goods exist. I would suspect the shock-hazard-lethality-paranoid Japanese market.

    AFAICS, all this grinder needs is a 3-Phase step-down transformer.

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    put a meter on the windings, if three phase the resistance will be identical between any two. Some other variant is bound to have one different

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    I would suggest that you look at the control transformer input voltage setting. That should tell you what voltage the machine is wired for.

    SAF Ω

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    Quote Originally Posted by JST View Post
    I have seen 120v 3 phase motors before. Usually to get an advantage when running at 240V 120Hz (and double speed).etc.

    Pictures of the nameplate?

    Is any wire conneted to the case?
    Here are a few pics of the motor and nameplate.
    20180304_124644.jpg20180304_124800.jpg20180304_123834.jpg20180304_123630.jpg

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    I managed to get my phone into the cabinet and snap a few of the table motor.

    It's a 115 v cap start 1/2 hp single phase basic motor fed by 2 wires ( hot and neutral )

    20180304_123249.jpg 20180304_123508.jpg

    Here is what I'm able to determine so far without using a meter which I didn't have with me at the time I took the pictures.

    The power inlet wire is a 4 conductor SJ cord with green and white tied together and connected to L1, red to L2, and black to L3 of an Allen Bradley re-settable switch with 4 terminals across the top.
    The AB switch is for the 3 wire spindle motor. The table motor is controlled by a simple toggle switch in a handy box by 2 power wires feeding from L1 and L2 of the AB switch.

    T1 goes to the spindle motor through a heater.

    T2 feeds directly into the spindle motor.(no heater)

    T3 leads to spindle motor through a heater.

    Terminals 4 on right have no connections.

    By process of elimination,

    1) L1 and L2 must be a 115 hot and neutral as it feeds the table motor,

    2) L1 ties together 2 of the SJ input wires (guessing neutral and ground) so power input is 3 wire .

    3) T1 and T2 must be 115 v single phase to the spindle motor.

    So what is L3/T3 into the spindle motor and why is it passing through a heater.



    I will ohm out the wires on the spindle motor tomorrow and post back my results.

    20180304_125809.jpg 20180304_125749.jpg 20180304_125837.jpg

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    checked resistance across motor leads.

    1-2= 4.7 ohm
    1-3= 6.5 ohm
    2-3= 6.5 ohm

    no wires to frame , no continuity from leads to frame
    Last edited by MikeMM; 03-05-2018 at 06:52 AM. Reason: additional info

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    A single phase 115V non-reversible motor has 3 wires. If reversible it has 4.

    2 of 3 will be run winding, the last will be the start winding. Start is likely to have higher resistance. If they are pretty similar, then it is likely a capacitor start motor, but it could be a "PSC" motor that uses a start/run capacitor that is smaller than a start type, and not "electrolytic".

    I see a "1" stamped on the motor plate, so whatever it was, it seems now to be a single phase. Is there a capacitor anywhere near it?

    This may be a case where it all has to be traced out and drawn as a schematic, to see what was done, and why.

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    Assuming you have standard color coding on your wires, the first thing to do is get the green wire off the starter and connect it to the machine frame. This is a big electrical code violation. The green(grounding conductor) and the white (grounded conductor) should only be connected together at the service entrance box and never connected together in end use equipment. Even in subpanels, they have to be kept separate.

    The two terms sound very similar (grounded and grounding), but they are for very different purposes.

    The grounding conductor is there to provide a path from the equipment to ground that will keep the machine frame near the ground potential. If there is leakage or a short to the machine frame, you are protected from electrical shock should you touch the machine frame and something grounded at the same time. In the best case, the ground makes the breaker trip.

    The grounded conductor is a power carrying conductor that is at ground potential at the electrical box. It has nothing to do with grounding, and should never be connected to anything except electrical system terminals. This system allows 220 volt services with the maximum voltage away from ground potential of 120 volts.

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    Quote Originally Posted by JST View Post
    A single phase 115V non-reversible motor has 3 wires. If reversible it has 4.

    2 of 3 will be run winding, the last will be the start winding. Start is likely to have higher resistance. If they are pretty similar, then it is likely a capacitor start motor, but it could be a "PSC" motor that uses a start/run capacitor that is smaller than a start type, and not "electrolytic".

    I see a "1" stamped on the motor plate, so whatever it was, it seems now to be a single phase. Is there a capacitor anywhere near it?

    This may be a case where it all has to be traced out and drawn as a schematic, to see what was done, and why.
    I agree on the phase stamp, it does look like something previously stamped was crossed out and replaced with a 1.
    Maybe they made a mistake on the assembly line and instead of replacing the label, they just said to heck with that, I'll just edit the nameplate.

    There is no external capacitor, I have seen motors with internal capacitors but not of this vintage. This motor is about 9 inches in diameter with big heavy end bells. Doesn't make sense to put internal capacitor.

    Is it possible that this is a repulsion start induction run motor? If so, I believe 3 wire would make it reversible?

    I also forgot to mention the motor is a dual shaft if that makes any difference.

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    Quote Originally Posted by wheels17 View Post
    Assuming you have standard color coding on your wires, the first thing to do is get the green wire off the starter and connect it to the machine frame. This is a big electrical code violation. The green(grounding conductor) and the white (grounded conductor) should only be connected together at the service entrance box and never connected together in end use equipment. Even in subpanels, they have to be kept separate.

    The two terms sound very similar (grounded and grounding), but they are for very different purposes.

    The grounding conductor is there to provide a path from the equipment to ground that will keep the machine frame near the ground potential. If there is leakage or a short to the machine frame, you are protected from electrical shock should you touch the machine frame and something grounded at the same time. In the best case, the ground makes the breaker trip.

    The grounded conductor is a power carrying conductor that is at ground potential at the electrical box. It has nothing to do with grounding, and should never be connected to anything except electrical system terminals. This system allows 220 volt services with the maximum voltage away from ground potential of 120 volts.
    Yes, as wired with SJ cord, it is a big safety hazard. If it was wired up with metal conduit or BX, at least the frame would be grounded and protect the operator through the EMT or BX casing.

    As far as tying the neutral to the ground in the machine, I do see it on the output of power conditioner / isolation transformers all the time. Of course the frame is grounded as well. Note the lower terminal in the picture. It passes electrical inspection every time. Go figure. I agree with you that it should only be done in the main panel,



    20657.jpg

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    Well I opened the motor and its not a repulsion induction. I am no expert but I have seen enough single phase windings to be able to identify the start and run windings in their 90 degree offset arrangement. These windings are symmetrically wound around the stator which leads me to believe it is a 3 phase motor. Can someone confirm this?

    20180306_180702.jpg20180306_180801.jpg20180306_180815.jpg20180306_180830.jpg

    If it is 3 phase, then L1, L2 and L3 must all be hot leads, not a hot and neutral on L1 and L2 as I previously assumed.

    Here is where I screwed up.

    I took a closer look inside the electrical box and where I thought the green SJ and white SJ were tied together by a white jumper, I was wrong. The white jumper I thought that came off L1 terminal was actually originating from a chassis screw behind L1 and obscured from view. L1 only has the white SJ and no white jumper as I thought I previously saw.

    At least that makes sense that the spindle motor is 3 phase and is powered by the white, red and black SJ leads while the table motor is powered by the L2 hot lead and the green SJ lead as the neutral. The grinder still needs to be grounded because it is currently grounded to the neutral line which is wrong.

    The question remains what voltage is the motor. The name plate shows 110 v but with the phase data possibly altered, is it possible/probable the motor was rewound for 230?

    How can I safely test the motor? Should I test it at 230V through the AB switch and rely on the heaters in the switch to trip if overloaded by voltage mismatch? I have a clamp on ammeter that I can monitor the current draw from each phase.

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    A surface grinder has little reason to have the motor reversed.

    And, don't forget, a single phase non-reversible single voltage motor can have 3 wires. The run winding is a pair, and the start winding is between the 3rd wire and one of the others. There would be a capacitor in series with the start winding, or else the start winding would be a different resistance. There would also be a switch to disconnect power from the start winding.

    So taking into account the altered dataplate, and the 3 wires, and also noting that the wire-to-wire resistances are not all closely similar, I do not know that we can assume it is 3 phase.

    It is 1725 rpm, therefore 4 pole. The wire connection bundles are two, not three, and the winding method is normal. Nothing there says 3 phase, in fact it seems to say single phase.

    Odd, to say the least. Can you make an overall wiring diagram? I am not clear on what is who from the pictures of the starter box, which I assume is the only electrical box.

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    Well, 3 phase 110V does not exist, so it's hard to imagine they would wind it that way. The only remove possibility is that they were intending on using a VFD and running the motor at 220V 120Hz, so they had it re-would as 110V so that they could do this without losing torque. But why bother with all that on a 4 pole motor? You could just buy a 2 pole motor and run it at 60Hz. The whole 110V thing makes zero sense.

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    Default schematic

    grinder-schematic.jpg

    Its not just an electrical box, its a manual start stop 4 pole switch with a thermal overload as noted by the 2 heaters. The 2 heaters are in circuit on t 1 and t3. ther is no heater for t2 and t4.

    The picture rotated, sorry I have no idea how to fix it.

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    Default success

    I can now confirm regardless of what the nameplate says, it is a 230V 3 phase motor.

    I decided to connect the motor without a load to a 20A 3 phase breaker the electrical panel through the control switch. I flipped the switch and was ready to immediately kill the power depending on what happened. No funny noise or hum and the motor spun right up to a smooth almost silent running state. I let it run for about 5 minutes while keeping an eye on the current draw which was almost immeasurable on a 60 amp scale. my meter has 2 scales, 60A and 300A.

    I then attached the belts to the spindle and restarted the motor and it was running the grinding wheel backwards. I killed the power and flipped 2 of the leads. The motor reversed direction and I tested the grinder on a piece of steel and it was beautiful. the amp meter deflected slightly whenever the wheel made contact. I let it run for 20 minutes and the motor barely got warm.

    Thanks to all who took the time to read and post replies. Hope to pay it forward when I can.

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    Quote Originally Posted by MikeMM View Post
    Thanks to all who took the time to read and post replies. Hope to pay it forward when I can.
    Give the next guy the up, and fix the motor tag...

    SAF Ω

  21. Likes JST, MikeMM, JLarsson, JohnEvans liked this post
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    Quote Originally Posted by MikeMM View Post
    grinder-schematic.jpg

    Its not just an electrical box, its a manual start stop 4 pole switch with a thermal overload as noted by the 2 heaters. The 2 heaters are in circuit on t 1 and t3. ther is no heater for t2 and t4.

    The picture rotated, sorry I have no idea how to fix it.
    Just so you understand this issue:
    Prior to 1971, it was perfectly legal to have OL heaters on only 2 legs of a 3 phase controller. After a phase-in period of maybe 7 or 8 years, it became a code violation. But if not inspected, nobody was going to force you to go that way. What that does give you though is an idea of how old that is... no NEWER than 1978, likely older than that.


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