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08-03-2004, 02:27 PM #1
I recently purchased a 3/4HP, six-pole Emerson three-phase motor on eBay.
The model numner is P63SYTBA-3781
The Cat. number is 6123
The wiring connections on the motor label are confusing. For both low and high voltage, the same wiring configuration is shown. This is contrary to every other dual-voltage three-phase motor I've seen. Is the label likely to be in error? Here is a photo of the label:
The motor is in my benchtop drill press, and is powered by a VFD, at 230V. I'd like to avoid smoking anything, if possible...
Darron R. Birgenheier
08-03-2004, 02:39 PM #2
08-03-2004, 04:11 PM #3
darron, am I missing something? When I look at the picture I can clearly see a difference in the wiring configurations:
The Low Voltage shows: L1-1-7, L2-2-8, L3-3-9, and then 4-10, 5-11, 6-12
The High Voltage shows L1-1, L2-2, L3-3, and then 7-4, 8-5, 9-6.
08-03-2004, 04:21 PM #4
Agree, but even considering the difference, I've never seen a diagram like that. It's almost a co-mingling of 9- and 12-wire diagrams.
08-03-2004, 04:25 PM #5
Oops- I never noticed the little lines in between the numbers.
Still confusing, though, as the diagram is still non-standard.
Should I risk wiring as shown in the diagram? I'm hoping the VFD's overload protection will save the motor if something is wrong. The VFD is 3/4HP rated, same as the motor.
08-03-2004, 04:52 PM #6
Got a multimeter?
If so, connect exactly as shown in both diagrams, measure resistance between L1-L2, L1-L3, and L2-L3. Do for both low and high voltage connections. Post here and well see.
08-03-2004, 05:53 PM #7
I am by no means a motor expert, so I had no idea whether the diagram looked "normal" or not. All I could tell was that there was a difference between the two configurations.
Maybe the fact that it is a 6-pole motor (rather than 2 or 4-pole) has something to do with it? Emerson is a pretty well known motor company; I would tend to trust them...
The VFD should protect itself and the motor, so I wouldn't worry too much about damaging anything. But if it isn't wired properly, it won't run "right".
08-03-2004, 08:27 PM #8
I to would like to see the results of a Ohm. meter test of leads too. Somewhere T10, T11 and T12 have to be connected to some of the other leads internally. If this is a 12 lead configuration motor, your coils should be:
T1 ---> T4,
T2 ---> T5,
T3 ---> T6,
T7 ---> T10,
T8 ---> T11,
T9 ---> T12.
In a Delta configuration for high voltage, the leads should be connected:
L1+T1 ---> T4+T7 ---> T10+T2
L2+T2 ---> T5+T8 ---> T11+T3
L3+T3 ---> T6+T9 ---> T12+T1
Or in a Wye configuration for high voltage, the leads should be connected:
L1+T1 ---> T4+T7 ---> T10
L2+T2 ---> T5+T8 ---> T11
L3+T3 ---> T6+T9 ---> T12 and tie together (T10+T11+T12)
(Where + means to tie together)
But this motor on high voltage, T10, T11 and T12 aren't connected (according to the data plate). So I think they must be connected to other leads internally or tie together to form a Wye. I would be curious to know which.
[This message has been edited by Webb Wyman (edited 08-03-2004).]
08-03-2004, 10:06 PM #9
"But this motor on high voltage, T10, T11 and T12 aren't connected (according to the data plate). So I think they must be connected to other leads internally or tie together to form a Wye. I would be curious to know which."
On this motor, the windings are operated in true parallel, when wired for low voltage.
Hence T10, T11 and T12 are connected to T4, T5 and T6, respectively, when wired for low voltage.
However, on this motor T10, T11 and T12 are internally connected, thereby forming a Wye.
Hence, T10, T11 and T12 are not connected, when wired for high voltage.
(If these were connected to anything, these would be connected to each other. The manufacturer has saved the owner the trouble of making this connection).
On six-wire motors, there is no provision for truly paralleling the wingings, so both Wyes float with respect to each other, when wired for low voltage.
On true twelve-wire motors, T10, T11 and T12 are the endings of the lower half of the Phase A, Phase B and Phase C windings, respectively, and these will always be connected together when the motor is wired for Wye operation, and will always be connected to the start the upper half of another phase, if connected for Delta operation.
So, this so-called twelve-wire motor is really just a six-wire Wye-connected motor, for which a provision has been made to truly parallel the phase windings.
08-03-2004, 10:32 PM #10
Once again, I am amazed at the wellspring of knowledge that is this forum. Answers to my questions are quick, detailed and accurate.
Here are the results of my Ohmmeter testing:
Motor wired as "low voltage", according to data plate diagram:
Impedance in Ohms of the windings:
Motor wired as "high voltage", according to data plate diagram:
Impedance in Ohms of the windings:
Does this all seem good?
I used wire nuts to make the connections. Although I do know how to use wire nuts properly, I prefer a connection to be soldered and insulated with tape or heat-shrink tubing. Is this acceptable practice for motor wiring? I prefer the soldered connections if for no other reason than neater appearance. With the large bundle of wires being stuffed into the rather small junction box on the motor, every bit helps...
08-03-2004, 10:52 PM #11
Thanks Peter for what should have been obvious to me. The post I referred to above contains this segment:
You're good to go with the motor.
Personally, I rather use wire nuts compared to solder and tape. If you know how to use the nuts properly, they actually offer quite superior protection from phase to ground shorts compared to solder and tape. Motor vibrations can erode tape and expose the bare solder and copper, especially at sharp points. For this reason I use rubber tape first over a solder joint, then electrician vinyl tape. Even with that, wire nuts are better. They run cooler than soldered joints, due to the fact that solder actually has quite a bit of resistivity compared to bare copper/copper.
The main secret with using wire nuts is NOT to twist the wires together beforehand, and to use the correct nut size. You hold the wires to be joined next to each other in a straight row, place the wire nut over the tops, and twist to firm resistance. Done that way, it will not come undone, even with vibration.
08-04-2004, 12:21 AM #12
Well, I just gave the motor the old "smoke & flames" test. It runs! Thanks for all the good advice. It seems like a great motor.
The VFD I am using is a rather large-cased Lancer GPD 402 (rated at 3/4HP, same as the motor). The VFD was new old stock when I bought it on eBay a year or two ago, perhaps as much as 15 years old. It is primitive enough to require DIP switch settings to program it’s few functions. It seems to work quite well, though. The motor is a little noisy with harmonics at some speeds, but not bad. I have the VFD set to run from 5Hz to 120Hz, it’s maximum range. 120Hz seemed reasonable for a six-pole motor, since it's only going 2400RPM at 120Hz. Wow, that six-pole motor spindle turns slowly at 5Hz. The motor label says nothing about being VFD rated, so I don’t know how long I can run that slowly without overheating. The VFD can be programmed to run the motor at 50%, 100% or 150% of normal torque at low speeds. I’ll leave it at 50% for now, just to be safe.
The drill press I have this setup on is a Taiwan-made Jet brand, about 15 years old. It had a 1/2HP single-phase motor on it originally. It was enough power most of the time, except when running a 5/8” drill though some heavy-wall box-section steel tubing, when it would occasionally stall. I realize that I’ll only get the full 3/4HP out of the new motor when the VFD is set at 60Hz.
The original setup had step pulleys on both the motor and spindle, and an intermediate step pulley between, giving 16 speeds. This was OK, but changing the position of the two belts could be a pain, and I never seemed to get just the speed I wanted. Also, at higher spindle speeds, the whole drill press would shake quite vigorously. I traced this to a sloppy pivot point on the intermediate pulley swivel.
With the new motor/VFD, I removed the intermediate pulley, and flipped the motor pulley top-to-bottom. This gives direct drive between the motor and spindle pulleys. This still allows four speed ranges, with a fifth range to be added when another larger single pulley gets added on top of the stepped motor pulley. The extra pulley will be needed to get spindle speeds as high or higher than I got with the original setup. I wanted the six-pole motor so I could run very slow spindle speeds for tapping, reaming, etc. Is tapping practical in a drill press? The VFD can be set to reverse quite quickly, and it has a separate switch for direction control.
I have a cheap DRO that I also bought on eBay:
It will be mounted to the front of the head casting. It is a bit long, though, and will protrude up into the spindle pulley area. Can it just be shortened, or is there something electrical in the “bar” that would be harmed when I saw the top end of the bar off?
I will probably just use a stainless hose clamp around the quill to mount a block. The bracket on the bottom of the DRO’s “bar” will be attached to the block, and the “slider” portion of the DRO will be attached to a bracket on the head casting.
I’d also like to install a digital tachometer. Any ideas on a cheap, easy way to do this? I could not find any good deals on a true industrial tachometer, with optical or magnetic pick-up. All I could think of was to use a magnetic-pickup bicycle speedometer. I determined that if the correct wheel diameter was programmed into the speedometer, the reading in MPH would actually correspond to RPM. For example, 122.5MPH would mean 1,225RPM.
[This message has been edited by darronb (edited 08-03-2004).]
08-04-2004, 01:43 AM #13
"I rather use wire nuts compared to solder and tape. If you know how to use the nuts properly, they actually offer quite superior protection from phase to ground shorts compared to solder and tape."
A "compression" connection (wire nuts, properly applied, or crimp connectors, also properly applies) are superior to soldering.
A fault could cause a soldered joint to heat beyond the melting point of the solder, and surely beyond the melting point of PVC tape, and cause an open or a line to ground fault, which might prevent proper activation of the motor's protective device, or cause a skock.
Never "tin" a conductor before applying a compression connector ... it might cause a fracture in the conductor, and thereby result in a poor or failure prone connection.
08-04-2004, 01:47 AM #14
What is being done in this connection table:
is the traditional Wye (high voltage) and the traditional dual floating Wye (low voltage) connections.
What was specified and implied in the first illustration for low voltage is the fully paralleled connection, where T4, T5, T7, T10, T11 and T12 are connected together.
[This message has been edited by peterh5322 (edited 08-03-2004).]
08-04-2004, 03:07 PM #15
Any overheat that will melt lead/tin
solder out of the wiring connections in
a motor is going to have other, more
serious consequences besides having the
connection go open!
A properly soldered connection will
have a lower resistance than a wire-nutted
one. Both types have acceptably low
resistance for normal use however.
I solder and then heat-shrink with two
layers. I've never seen any vibration
related fails from the shrink tubing
begin rubbed through.
Consider - if tape on a joint is going
to get rubbed through, what will that
do the actual wire insulation?
08-04-2004, 03:19 PM #16
"Any overheat that will melt lead/tin
solder out of the wiring connections in
a motor is going to have other, more
serious consequences besides having the
connection go open!"
"Soldered" joints in an integral HP motor are usually brazed, not soldered.
At least that's the way motors are rewound around here.
Fractional HP motors, especially high-volume, "commodity" motors, might be lead-tin soldered. These often are "impedance protected", too, so no winding fault is likely to result in fault currents which can melt the solder.
08-04-2004, 03:39 PM #17
Jim, I disagree with you on soldered connection having lower resistance. Even if the joint is properly soldered.
A couple of years ago I built myself a milliohmeter out of a cheap digital multimeter, variable pot, and a Duracell D flashlight battery. It uses the principle of the four wire Kelvin circuit,
I built it mainly to test connections between ground wires (equipment ground connections; grounding electrode connections; receptacle ground connections). I'll confess to being a compulsive neurotic about electrical safety, and the reason I built it was to ensure that phase converters I build are solidly grounded, and that anything connected to them in a shop is too. I'd be happy to post a pic of this contraption, which is mounted on a bread cutting board. I use it at least once a week.
Anyway, I've tested all sorts of low resistance grounds with this milliohmeter. This includes wire nut connections and equivalent soldered connections. I know how to solder correctly. I can tell you that a properly-done wire nut junction will beat a soldered connection. If you like, you can send me two samples and I'll read them on my meter.
Solder is pretty much taboo in heavy industrial electrical work. The higher resistance compared to mechanical means (lugs, sleeve crimps, c-taps) means a soldered joint runs hotter. Under stress, the solder may in fact melt.
Another thing I strongly believe in is cadweld ground rod connections. After a year of use outside, the cadweld is significantly lower in resistance than a ground clamp.
I agree with you in the latter part of your post. Shrink wrap is great -- far superior mechanically to tape. Use it whenever you can.
08-04-2004, 05:04 PM #18
Hmm. Sounds like a solder vs wirenut
We ought to set the ground rules first
though. Kind of wire, make up of
joint, prep, etc.
I'd be happy to make up a set of test
joints, measure them, and then ship
them to you for a second opinion.
I would use stranded wire, and the wirenuts
in my house wiring stash, which are somewhat
better than the el-cheapo ones.
I would make the solder joint by stripping
and twisting the conductors for about three
wire diameters or so.
08-04-2004, 06:24 PM #19
Interesting results. I took a few pieces
of number 14 copper wire and made three
1) A soldered joint,
2) A wire-nutted joint,
3) A short stub of wire, with length
appx equal to the total length of
wire of each of the test joints.
I used a four wire bridge made by HP
to test each one.
Short length of wire = 0.02 milliohm
Soldered joint = 0.12 milliohm
Wirenut joint = 0.23 milliohm
I'd be happy to mail these to you for
your evalution - and if you do the same
with a similar set fabriated at your
end, I'll measure them here. I'd
be curious to see what your meter reads
I did an 'average' job of making up the
wirenut - you can do the post-mortem on
it and see if there's a better technique
The (uninsulated) solder joint is also
done in an average manner - with a length
of about three wire diameters or so.
08-04-2004, 06:54 PM #20
Jim, great data. I'll do the same. The results I referred to in my post above were on SOLID wire, I believe 12 gauge, except for the ground rod stuff which was all #4 soft stranded copper.
I'll use solid again with 60/40 solder and repeat your ground rules, then post my results. If they conflict, we can trade as you suggest.