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[How do I?] Motor wiring puzzle

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I am trying to help a friend get a motor wired up and it has me stumped. The motor is 5hp single phase 240v 3420rpm TEFC with a centrifugal switch for a start capacitor. It was purchased surplus with no documentation and missing capacitor(s). Here is the tag:
grizzly-motor.jpg
Grizzly has been no help.

There are two red wires, two black wires, and one yellow wire coming out of the motor.

R1 connects to one of the centrifugal switch contacts. It is open circuit to everything when the contacts are open. R2 connects to the other side of the
centrifugal switch. Simple enough but I have not been able to make sense of the connections to the windings.

I measured the following resistances between pairs (measured with 4-wire connections, variation in the contact resistance is about 0.01 ohm):
Bk1 -- Bk2 0.206 ohm
Bk1 -- R2 0.904 ohm
Bk1 -- Y 0.006 ohm
Bk2 -- R2 0.936 ohm
Bk2 -- Y 0.197 ohm
R2 -- Y 0.930 ohm

All of the wires are > 1500 Mohm to the case.

I would appreciate any insights or advice on how to proceed.

Dave
 

Comments

there is something wrong with the resistance readings! there should be two distinct windings, start and run, and there should be no connections between the two. the connections should be like this,
1546781633224.pngThe start coil should have a highrer resistance than the run coil, try using the multimeter on a different resistance setting. have you had a look inside the motor? Can you send some pics of the motor terminals, is there a wiring diagram inside the terminal cover?
Phil
 
Here are the manuals for the only two 5hp 3450 single phase motors that I could find on the Grizzly page:

https://cdn0.grizzly.com/manuals/h5390_m.pdf
https://cdn0.grizzly.com/manuals/h5389_m.pdf

Both have wiring diagrams and specs for the capacitors.

They are also the only two 5hp motors listed in the 2011 and 2017 paper catalogs. The first one "H5390" has a standard mounting base, the H5389 has a mounting bracket for a table saw.
 
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there is something wrong with the resistance readings! there should be two distinct windings, start and run, and there should be no connections between the two. the connections should be like this,
View attachment 284221The start coil should have a highrer resistance than the run coil, try using the multimeter on a different resistance setting. have you had a look inside the motor? Can you send some pics of the motor terminals, is there a wiring diagram inside the terminal cover?
Phil
I agree that there is something screwy about the resistance readings so they have been checked multiple times. Measured with a HP 3468A
multimeter in 4-wire resistance mode. My confusion was even greater in the beginning since the centrifugal switch contacts had significant and non-reproducible resistance. Holding the switch open isolated R1 and resulted in the measurements listed. They are consistent with the following schematic:
schematic-v1.jpg
Which doesn't match any that I have been able to find on the internet. It looks more like a multispeed motor but that would require an external connection to the junctions between L2 and L3.

Looks to me like BK1 and BK2 are the line connections and the start capacitor should be connected between R1 and Y.
R2 is possibly for a run capacitor but if the other end is connected to either line then running current would flow continuously through the high resistance winding L1 and the current through the two halves of the main winding would be unbalanced. With 240V at 25A I don't want to get it wrong--the magic smoke release could be exciting.

There is no wiring diagram in the junction box. The motor is at my friends place. I'll get some photos of the wiring tomorrow.
 
Here are the manuals for the only two 5hp 3450 single phase motors that I could find on the Grizzly page:

https://cdn0.grizzly.com/manuals/h5390_m.pdf
https://cdn0.grizzly.com/manuals/h5389_m.pdf

Both have wiring diagrams and specs for the capacitors.

They are also the only two 5hp motors listed in the 2011 and 2017 paper catalogs. The first one "H5390" has a standard mounting base, the H5389 has a mounting bracket for a table saw.
I have been looking at the Grizzly site. The H5390 and H5389 motors both have six wires. This one only has five.
I have been working my way through all the 5 hp machines on their site, looking at the wiring diagrams in the manuals and so far have not
found a match.
 
Some of your numbers don't make sense (measuring very low resistance can be a bit of a challenge)

You stated:
BK1-> BK2 = 0.206
BK1-> R2 = 0.904
BK2-> R2 = 0.936 (If the other two are correct this should be about 1.110

I suspect "Y" may be for an overload protector.

Deleted bogus drawing.
 
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Hi Dave: I agree with most everything you said in post #4, the only questions are how big of a start capacitor you need, and if the motor requires a run cap. Some more online research will probably get you in the ballpark, I would say the start cap would have to be at least 200 uF at 250 vac for a motor that size. No idea on the run cap (if required). The motor will run without a run cap it just won't develop maximum torque. A too-small start cap will still start the motor but it will take longer to get up to speed and have less starting torque as well.
Does the motor have pairs of tapped holes in the case for capacitor covers? Two sets of holes would indicate two covers/two caps originally.
Mark
 
working voltage for a start or run capacitor should be twice supply voltage, so at least 450v Wkg. Yes I agree, it does look like a dual voltage, but the plate clearly states 240V, Odd! Is it perhaps one of those single/three phase motors (perhaps sourced from China, even though it says Taiwan) that is sometimes connected as a plain 240v three phase, and "converted" to single phase by the addition of capacitors and swapping the windings around? Doesnt explain the centrifugal switch, but if both switch leads are present at the connector box, you could configure it any way you wanted. Keep looking, I will give it some more thought!
 
RIGHT!! You are in USA where there are two "hot" wires for 240v systems, yes I agree with your wiring method.
Looks to me like BK1 and BK2 are the line connections and the start capacitor should be connected between R1 and Y.
I am in the UK, where we only have 240V single phase, with 1 hot wire, and a neutral wire! Sorry for the confusion. Try the motor wired as above, if it starts and runs quietly, and doesnt get excessively hot, You have got it!
 
I agree that there is something screwy about the resistance readings so they have been checked multiple times. Measured with a HP 3468A
multimeter in 4-wire resistance mode. My confusion was even greater in the beginning since the centrifugal switch contacts had significant and non-reproducible resistance. Holding the switch open isolated R1 and resulted in the measurements listed. They are consistent with the following schematic:
View attachment 284225
Which doesn't match any that I have been able to find on the internet. It looks more like a multispeed motor but that would require an external connection to the junctions between L2 and L3.

Looks to me like BK1 and BK2 are the line connections and the start capacitor should be connected between R1 and Y.
R2 is possibly for a run capacitor but if the other end is connected to either line then running current would flow continuously through the high resistance winding L1 and the current through the two halves of the main winding would be unbalanced. With 240V at 25A I don't want to get it wrong--the magic smoke release could be exciting.

There is no wiring diagram in the junction box. The motor is at my friends place. I'll get some photos of the wiring tomorrow.
Wired it up last night with a 300 uF start capacitor at R1-Y and it spins up very nicely, draws 13.5 A with no load. Don't have any way to test it under load so I can't tell if adding a run capacitor has any effect. It seem happy with 30 uF between R2 and BK1. Nothing gets hot.

Thanks to all for your help.

Dave
 
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