I am working on completely rewiring an overhead crane and I am having a little trouble trying to figure out how to wire up the bridge motor to my vfd , it only has 6 wires coming out . T1 T2 T3 , and 3 relabeled wires with letters that do not match the dataplate . it is a manning maxwell & moore motor , and says single speed two voltage series and parallel star . and according to the plate i should have 9 wires from T1-T9 but i only have 6 wires .
3 phase motor wiring help
- Thread starter Davtronic
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zbang
Senior Member
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- Roughly 5346 miles from Earls Court
Got some photos? That might help.
synchro
Senior Member
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- Chicago, IL
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- EE
Just a guess, but perhaps the leads 4,5,6 in the diagram below were connected inside the motor by someone and are no longer accessible. If that was the case then it now has two star configured sets of windings that could be wired in parallel for low voltage, but not for high voltage with only the 6 leads that are available.
Check if T1, T2, and T3 have continuity between each other, but are not a dead short. If so that would lend some credence that the internal connection mentioned above has been made.
Do the same measurements on your other 3 leads to see if they also have continuity with each other, and if so they could be the 7, 8, 9 in the diagram below.
If this checks out then you can do further identification of the wires as in the following video:
Check if T1, T2, and T3 have continuity between each other, but are not a dead short. If so that would lend some credence that the internal connection mentioned above has been made.
Do the same measurements on your other 3 leads to see if they also have continuity with each other, and if so they could be the 7, 8, 9 in the diagram below.
If this checks out then you can do further identification of the wires as in the following video:
thanks for your replies , and yes i do have some photos but i cannot figure out how to attach them ? it wants me to enter a link to attach a photo ? i checked and the dataplate shows the very same configuration you have in the photo above but sorry our internet filter does not allow video, also on the dataplate on my motor here it has the low voltage and low voltage amps hammered out so i am assuming the were running high voltage , and i am running this motor with a vfd and tried both sets of 3 and it hums but doesnt turn . but i will go check the continuity .
ok i checked the wiring , 3 wires originally metal tagged as T1 T2 T3 measure 2 ohms between all 3 combinations and nothing to ground , but the second set of wiring which has no original markings but are labeled as H, Y, M, and M-Y = 11 ohms , H-Y = 137 ohms , M-H = 129 ohms and nothing to ground , i looked in the motor housing and the only thing i can find is T1 T2 T3 going to the rotor and H Y M going to the field .
kwired
Electron manager
- Location
- NE Nebraska
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- EC
If you have leads going to both stationary and rotor windings you don't have a basic induction motor that only has leads to the stator, you probably have a wound rotor motor and the HYM leads likely were not to have line voltage applied to them but rather be connected to equipment used to regulate current in them and in turn regulate motor speed. If so can probably tie them together and would result in getting "high speed" out of it.
Probably originally was dual voltage but has since been rewound but ony had leads brought out for incoming power and was internally fixed for only one supply voltage.
drcampbell
Senior Member
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- The Motor City, Michigan USA
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- Registered Professional Engineer
Is the rotor connected through three brushes and three slip rings? That would fairly-conclusively point to a wound-rotor motor.
If it was originally installed before 1990 or so, a wound-rotor motor is a likely choice, to provide variable speed before solid-state VFDs were available, reliable and/or economical.
But the rotor in a wound-rotor motor will have three identical windings, not 11, 137 and 129 ohms. Either it's some other kind or motor, there's some other explanation, (speed sensor? temperature sensor?) or there's a fault.
en.wikipedia.org
If it was originally installed before 1990 or so, a wound-rotor motor is a likely choice, to provide variable speed before solid-state VFDs were available, reliable and/or economical.
But the rotor in a wound-rotor motor will have three identical windings, not 11, 137 and 129 ohms. Either it's some other kind or motor, there's some other explanation, (speed sensor? temperature sensor?) or there's a fault.
Wound rotor motor - Wikipedia
en.wikipedia.org
Is the rotor connected through three brushes and three slip rings? That would fairly-conclusively point to a wound-rotor motor.
If it was originally installed before 1990 or so, a wound-rotor motor is a likely choice, to provide variable speed before solid-state VFDs were available, reliable and/or economical.
But the rotor in a wound-rotor motor will have three identical windings, not 11, 137 and 129 ohms. Either it's some other kind or motor, there's some other explanation, (speed sensor? temperature sensor?) or there's a fault.
Wound rotor motor - Wikipedia
T1 T2 T3 go to a set of brushes that connect to the rotor windings and they all have 2 ohms , its the lettered wires that have inconsistant ohms values .
drcampbell
Senior Member
- Location
- The Motor City, Michigan USA
- Occupation
- Registered Professional Engineer
If that's how you intend to run it, you might connect the HYM rotor leads together at the rotor, taking the brushes out of the circuit. If they're not there, they won't wear out or fail. While you're at it, set the brush spring tension to the minimum for the least drag and wear.
kwired
Electron manager
- Location
- NE Nebraska
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- EC
When you said there were leads to the rotor I suspected wound rotor motor, though I thought would be rare to have incoming supply leads go to the rotor, which you corrected this info for us - thank you.
Or even remove brushes altogether.
If that motor ever goes bad you can probably replace with a general purpose motor unless there is other characteristics that make it difficult to match up to the application, the wound rotor feature was basically for varying speed before the days of VFD's.
drcampbell
Senior Member
- Location
- The Motor City, Michigan USA
- Occupation
- Registered Professional Engineer
Even better. (though you might want to leave them with the motor, on the unlikely chance that someone in the future will want to reconfigure it back)
More power. Convert to doubly fed! Twice the power in the same volume.
kwired
Electron manager
- Location
- NE Nebraska
- Occupation
- EC
How long will that last? Isn't the rotor intended to have induced voltage on it and speed regulation is done by regulating the current via external accessory?
drcampbell
Senior Member
- Location
- The Motor City, Michigan USA
- Occupation
- Registered Professional Engineer
Yes. See the Wikipedia article cited above.
Doubly-fed electric machine - Wikipedia
en.wikipedia.org
That’s one control mode where you just vary resistance but that’s without slip energy recovery. Once you recover the energy you get an efficiency or alternatively a torque boost. They are used in windmills where space is a premium for the high power density.
I left the brushes and everything as it was , but now i have another question , and let me know if i need to start a new post instead , but on this same motor i have it running at 20hz for low speed and its still plenty fast for low , but i had someone tell me i dont get to go to low on the frequency especially if it is not vfd rated and doesnt have a fan , can i take it farthur down like 10hz ?
synchro
Senior Member
- Location
- Chicago, IL
- Occupation
- EE
Actually, if it does have a fan then that's when the problem can arise at low speeds because the fan is needed but it provides inadequate cooling at low RPM. In your case if it was originally speed controlled down to very low RPM without needing a fan, then it should have adequate cooling for that situation.
I defer to members here with more expertise in motors like winnie, paulengr, Jraef, etc. if they think otherwise.
kwired
Electron manager
- Location
- NE Nebraska
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- EC
I'd have to agree with synchro on the fact that it was likely intended to have speed varied to begin with and this probably not much of an issue when it comes to heat management.
It may not have insulation like inverter duty motors have and if so at very least you may want a line reactor on the output of the drive to smooth the voltage wave out so it looks more sinusoidal to the motor, especially if operating @ nominal 480 volts, the peaks on 480 V VFD output can be well over the insulation rating of non inverter duty rated motor.
It may not have insulation like inverter duty motors have and if so at very least you may want a line reactor on the output of the drive to smooth the voltage wave out so it looks more sinusoidal to the motor, especially if operating @ nominal 480 volts, the peaks on 480 V VFD output can be well over the insulation rating of non inverter duty rated motor.
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