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AiR_GuNNeR
04-17-2010, 09:50 PM
I picked up a really nice 3HP, 3PH 3400RPM motor for $8.50 at an auction.
There was an old piece of paper taped to it that said "motor runs slow with current jumper settings.", but I put a $25 max bid on it. It looked like a very expensive motor, so I figured it was worth a $25 risk. Here is a picture of the same motor, (get a load at the price!).
http://cgi.ebay.ca/Grundfos-Heat-Exchange-Motor-MG90LA2-24FT115-C_W0QQitemZ200406810960QQcmdZViewItemQQptZLH_Defau ltDomain_0?hash=item2ea92d4150

I bought a TECO VFD a while ago, but have not used it up until now. I also have a 2HP 3ph motor on a mill I am rebuilding. I wired up the mill motor to the VFD and it works fine. It runs smooth from slow speeds up to full speed.

When I hook up this new motor and try to run it, it won't start rotating on its own. If I set the frequency to 5hz, and help the shuddering shaft to turn, it starts to spin and I can run it up to 60hz no problem and it comes up to its full 3400 rpm speed. It's pretty rough running until it gets up over 30hz. When it is trying to start on it's own, it sounds like something spinning and rubbing inside the motor as it is trying to start, (do these have internal starter motors in them with a clutch maybe?)

I have the VFD set to non vector drive for the time being.
Can anyone surmise what might be wrong?
Eric

PixMan
04-17-2010, 10:13 PM
It's an $8.50 motor, and acting like one. :D

Sorry, I couldn't resist.

A lot of how a 3 phase motor behaves at speeds lower than it was designed for has to do with the type of windings it has. I can only guess that the one you have has very basic windings that just don't work well at the lower frequency ratings. I've seen it before.

Does it start right up if you light it up at 60Hz?

AiR_GuNNeR
04-17-2010, 10:20 PM
I have the VFD set to ramp up to 60hz in 2 seconds. I'll try to reduce that to see what happens. It is setup in a Delta configuration for 220v use, (440 needs to set to Y).
Eric

Black_Moons
04-17-2010, 10:28 PM
Id take a multimeter set to ohms to it and see what the three windings read.
Im no expert at 3 phase motors, but it kinda sounds like one of your coils isent connected or isent connected up properly.

J Tiers
04-17-2010, 10:29 PM
Don't bother to try it again yet.

before that , get your ohmmeter or DVM, disconnect the motor from the line, and check resistance between the 3 terminals...... Odds are you will see a difference if it is a motor problem.

if OK, try it again.

a 3 phase motor will run on single phase if it is started, just like a single phase motor. better, actually, since it is entirely free to run, with no drag from the start switch. All the thousands running on 'static converters" are proof of that.

So a bad motor might not start without help, but would RUN without help if you get it turning by hand.

boslab
04-18-2010, 12:03 AM
tried it on a normal 3ph supply, does it grumble?, measure across each of the three phases on the motor, should have about the same resistance in Megohms, if not a phase winding is dieing.
mark

The Artful Bodger
04-18-2010, 01:19 AM
Eric, a 3 phase motor is mechanically very simple. If the resistance measurement between each of the 3 wires is similar the coils are probably OK, if there are some that are twice, or half, the other that might indicate incorrect jumpering of a multi voltage motor and might, conceivably, explain why it is reluctant to start.

If there is a rubbing sound that could be bad bearings or it might be crud got in between the rotor and the stator. It might also be a result of incorrect assembly is someone has had it apart.

metalmagpie
04-18-2010, 08:59 AM
open wiring box
disconnect all wires inside
now put on your strongest glasses and arrange for a strong light
now locate the wire numbers on each wire
now reconnect the wires correctly for your voltage
button up wiring box

AiR_GuNNeR
04-18-2010, 07:54 PM
Thanks for all the replies. The windings measure 2.4, 2.3, and 2.3 ohms so the windings look good. The scraping noise go away immediately once it gets a little bit of RPM behind it. That's why I'm thinking it is some kind of centrifugal clutch?
The wiring is pretty fool proof the way they have it arranged. For 440 volt, one side is supposed to tied together, and the other side, labled L1, L2, L3 goes to the three phased, (Y arrangement). For 220, they are setup the way pictured for a delta configuration. I can try arrangeing the colors to match up, although I don't think that is supposed to make a difference?
Eric
http://www.compufoil.com/images/scraping/motor.jpg

The Artful Bodger
04-18-2010, 08:44 PM
Deleted by me....

J Tiers
04-18-2010, 08:49 PM
IIRC the one wire shift is correct...... which is what your pic shows. That should be an IEC motor, which is a 6 wire motor, Wye/delta connectable.

The way it is wired, each color is a winding. So the windings are each connected between the top one and the next over on the bottom.

With the top shorted together and wires to each bottom coming in, it is Wye-connected.

With a connection top to bottom, it is now set up with each "dot" (or "+") coil end connected to the opposite end of teh next coil, in other words, for delta.

The only way to mess that up would be to get the wrong end of a coil, but they brought them out in two bundles...... that makes it easy to do right.

Dunno about a clutch...... shouldn't be one.

And a delta-Wye change is not 2:1, it is 1.73:1. 220V would become 380V..... 440 is 15% high for that... 240V would become 415V.

squirrel
04-18-2010, 08:54 PM
Are you sure the wires are connected for 220 Volt operation, that box looks like it could use a few more wires. Can you post a pic of the motor plate. The scraping might be the fan rubbing on the housing or a bad bearing. Does the shaft spin freely by hand?

AiR_GuNNeR
04-19-2010, 06:19 AM
Are you sure the wires are connected for 220 Volt operation, that box looks like it could use a few more wires. Can you post a pic of the motor plate. The scraping might be the fan rubbing on the housing or a bad bearing. Does the shaft spin freely by hand?

This is an EIC motor, (made in Denmark if I recall). Tiers nailed it as far as the wiring is concerned. The odd noise is coming from the shaft end. I don't hear it when I spin it by hand, and it goes away as soon as I get the motor spinning. Perhaps it's an inner fan blade spinning on the shaft because of the rotating field. My buddy has an RPC setup. I'll hook it up to that to see if it runs correctly. Perhaps it's just not suited for VFD control?
I may open it up to get the low-down on the noise if it doesn't work with the RPC
Eric

EVguru
04-19-2010, 07:02 AM
What's the base frequency set to on the drive?

I had a similar problem when I'd left a setting at 400Hz and the motor was getting only 50 volt at 50Hz.

Measure the phase voltage.

MaxHeadRoom
04-19-2010, 09:33 AM
Is it possible it was designed to run as an ECM motor?
Electronically commutated?
Many Heat exchange/Air conditioner/furnace motors are now using this type of motor.
If so it would have a permanent Magnet rotor.
A email to Grundfoss might clear it up.
M.

bborr01
04-19-2010, 10:34 AM
I had a south bend lathe that came with pigtail with 30A 250v 3ph twist lock on it. I re-wired the motor low voltage and it spun slow too.
Tried another motor and it spun slow too.
Finally pulled the plug apart and it had one of the hot wires switched with the ground. I switched them around and problem solved.
Something to think about.
Brian

AiR_GuNNeR
04-19-2010, 04:08 PM
What's the base frequency set to on the drive?

I had a similar problem when I'd left a setting at 400Hz and the motor was getting only 50 volt at 50Hz.

Measure the phase voltage.

I'm not sure. I have the max frequency set to 60hz, so I have to assume that it is scaling the voltage based on that.

EVguru
04-19-2010, 04:21 PM
I have the max frequency set to 60hz, so I have to assume that it is scaling the voltage based on that.

No, there will be another setting for the 'base' frequency. The maximum frequency could be lower or higher than that.

In my case I have the base frequency set to 50Hz (nameplate spec), the minimum frequency to 20Hz and the maximum to 135Hz (which allows me to get my Harrison up to 2000rpm).

The Artful Bodger
04-19-2010, 04:35 PM
Getting back to basics on this one...


A three phase motor usually has either three windings for a single voltage systen or six windings for a dual voltage system.

Some countries have two three phase voltages available where the high voltage is twice the low voltage and I think that includes the US? (220 and 440) Some countries have two three phase voltages available where the high voltage is not twice the low voltage.

Those other countries use a method of switching between wye and delta connections to get the desired voltage ratios but if I am not mistaken where the high voltage is twice the low voltage the voltage change is gained by switching coils in series or parallel.

So, if the high voltage is twice the low voltage there is probably no reason to worry about the question of delta and why.

One might expect a dual voltage motor with six windings to have 12 connections but it is common practice to internally connect three of the winding internally to a why leaving 9 external connections.

Does this motor have 9 connectors? The 6 wires and the three terminal strips?

Assuming it does:

First disconnect all wires then use the meter to identify which coils might be in a why, if you can find three wires, or the three terminals, are all connected to each other you have found the why.

Having found the internal why you can connect your supply to those three connections and the motor should run even though all other connections are left free. Although the motor should run normally it will have only half it full rated torque.

The next step is to attend to the other six connections. The requirement is to get each of these three coils in parallel and in phase with the appropriate leg of the already existing wye.

AiR_GuNNeR
04-19-2010, 05:17 PM
Artful,
It looks like the terminal strips are just jumpers. They don't have any wiring coming off of them underneath. The terminals are marked like this:
V2 W1
U2 V1
W2 U1
The cover shows a diagram for a Delta configuration like the photo, jumpered:
V2-W1
U2-V1
W2-U1

For a why connection, they show V2-U2-W2 together, and W1-L1, V1-L2, U1-L3

The motor plate shows two voltage ranges, with the 220 section having a capital D in it and the 440 range with a capital Y.

This motor appears brand new. When I took off the screw that is holding the terminal strip to the case, I could see into part of the winding. There isn't a spec of dust on them.

As curious as I am to see what's inside this beast, I hate to take it apart without a schematic for fear of messing something up.

I have to think this motor has three windings, each winding with its own wire color. One group of wires bundled to geter for each end of the coil. Jumpering all three wires of one bundle together and connecing the other bundle to power gives the Y, and joining them as in the picture gives a delta with each leg of the power going to the juncion of the coils. The Y configuration would have two coils in series between phases, and the Delta only one, so that makes sense from a voltage standpoint (440Y, 220D).

The Artful Bodger
04-19-2010, 06:20 PM
Hmmm, Eric, changing from delta to wye does not get twice the voltage as the coils are not in phase, the difference would I think be 1.7 something. However, maybe they do that anyway.


If the motor has only three windings and you connect three ends together and power to the other free ends as far as I can see you cannot make a mistake. So I am really scratching my head now!

About the only thing left to try would be to swap the end of one of the coils, i.e. take one end from the wye common and connect the other end of that coil to the common and power to the other end. I would not have thought that would make a difference but I might be missing something.

AiR_GuNNeR
04-19-2010, 06:40 PM
Hmmm, Eric, changing from delta to wye does not get twice the voltage as the coils are not in phase, the difference would I think be 1.7 something. However, maybe they do that anyway.

I guess what I was thinking was you would have twice the resistance between phases so it would make sense that the Y would be for the higher voltage profile.

I think next step is going to be hook it up to my friends RPC and see if it will spin up.

The Artful Bodger
04-19-2010, 07:47 PM
I guess what I was thinking was you would have twice the resistance between phases so it would make sense that the Y would be for the higher voltage profile.

J Tiers, post #11, gave the ratios, you cannot exactly add the phases together because they are not in sync each one being 120 degrees removed from the other two.




I think next step is going to be hook it up to my friends RPC and see if it will spin up. Good luck with that and as someone mentioned just make sure the plug is wired correctly! If it does not spin up you might like to try reversing one coil and if necessary two but if it still does not work I am afraid I would be right out of suggestions!:)

squirrel
04-19-2010, 07:54 PM
Is it possible it was designed to run as an ECM motor?
Electronically commutated?
Many Heat exchange/Air conditioner/furnace motors are now using this type of motor.
If so it would have a permanent Magnet rotor.
A email to Grundfoss might clear it up.
M.
I think you might correct that it is ECM.

AiR_GuNNeR
04-19-2010, 08:00 PM
I think you might correct that it is ECM.

From what I was reading, doesn't a ECM motor use a brushless motor controller to power it though? If it is an ECM motor, would there me any chance of it working off of regular 3phase? It runs great at a full 3400 rpm when I get it rotating and bump the frequency up to 60 hz.
There are several distributors in Michigan, but they are all plumbing type supply places. Apparently Grundfos is big into the pump industry.

The Artful Bodger
04-19-2010, 08:22 PM
I think you might correct that it is ECM.

I very much doubt it as the markings on the terminal block etc are very much like an induction motor.

squirrel
04-19-2010, 08:58 PM
From what I was reading, doesn't a ECM motor use a brushless motor controller to power it though? If it is an ECM motor, would there me any chance of it working off of regular 3phase? It runs great at a full 3400 rpm when I get it rotating and bump the frequency up to 60 hz.
There are several distributors in Michigan, but they are all plumbing type supply places. Apparently Grundfos is big into the pump industry.
More than likely no, running that type of motor requires sensing the back EMF from the windings for proper commutation. We could be all wet on this, a pic of the motor plate would help.

J Tiers
04-19-2010, 10:28 PM
That is a "bog standard" euro type induction motor......... we have several at the shop.

it also looks like it is wired right.

Now, an induction motor really has a hard time running "slow"....... unless it has a problem, like a bad winding, etc. They inherently run at nearly synchronous speed.

Most all VFDs will tell you the motor current, some will do it by phase.... So......

When you run the motor, does the VFD indicate a current that makes sense? Should be something like 40% of full load current at no load.

if you can get a current by phase, are they balanced? (if one phase wire is loose and not making contact, the motor is running single phase, and won't start. it may run OK once it is started...... phase ciurrents will show that up quickly.)

Does the VFD indicate ANYTHING odd? Most will tolerate a temporary overcurrent, without shutdown, but will do SOMETHING to show it. Invertek, which I am familiar with, typically light all the decimal points on teh display.... others may do something else.

I ran into this a while back, when we were testing some drive assemblies, but I canNOT recall what the issue was..... The motor was running "goofy-rough" and wanted to jump off the bench.....

One last thing...... you will be running it delta, for the low (220) voltage, so does the resistance indicate the same between each wire pair of the mains? Take the wires off the VFD and check from that end

The Artful Bodger
04-19-2010, 10:34 PM
J Tiers, I am suspecting that one of the coils is connected back to front but I am yet to figure out why that doesnt just make it run the other direction.

J Tiers
04-19-2010, 10:44 PM
J Tiers, I am suspecting that one of the coils is connected back to front but I am yet to figure out why that doesnt just make it run the other direction.

The problem there is that they have collected the wires in two bundles, and the bundles are correctly wired to the block as one would expect...

The wire would have to be bad from the factory.

Theoretically, that can be discovered with a small compass and a source of low DC current.

As for why it does not run backwards in such a case...... that is because the reversal of two MAINS wires reverses the phase rotation. Reversal of a coil set does not, it just puts one coil set out of phase with teh others.

The Artful Bodger
04-19-2010, 10:56 PM
Reversal of a coil set does not, it just puts one coil set out of phase with teh others. Ah, that would seem to be a logical explanation then as we have been told the motor is apparently quite unused it might have been duff from the factory. It does seem unlikely but at least something must be wrong.

AiR_GuNNeR
05-08-2010, 06:01 PM
Well, I finally got a chance to stop by my buddies house who has a RPC. We wired it in and it took right off! Oh, and I was wrong about the price I got if tor on the first post..it was $7.50, not $8.50.

I may give Teco a call and see if they have any recommendations for settings. Maybe the motor need higher voltage and or frequency to get it spinning initially or something. It's a real nice motor and quite expensive so I hate not being able to use it with a VFD.

J Tiers
05-08-2010, 09:33 PM
We were testing a bunch of assemblies that include a 2 HP VFD just yestereday at work. They are a control board and an Invertek "compact" VFD.

The technician had them all in the temperature chamber, at -40C, and two were not running well. The VFD made the right acceleration noises, but the test motors did NOT turn.

I cam over and hand-spun the shafts of teh test motors, at which point they spun right up, but grumbled a bit as they did.

I said " those motors are single phased", and told him to check the wiring.... He said it was good, and finished the test with the hot end (+60C) for the other units in the chamber.

Well, when he went to take them out, lo and behold, the connectors had come off a phase wire on each of the "bad" units. So the motors WERE "single phased", but not because of any low temp problem in the VFD assembly as I suspected from his initial report. Instead, it was because the wires were off, and those two need to be re-tested over the full range.

What each of the motors did was as follows:

1) shaft didn't turn, although VFD noises sounded right for acceleration (these are not vector drives)

2) when shaft was started, they grumbled but did come up to speed. Shaft was hard to start turning

3) When the VFD was given a stop command, the motor came to a halt, but looked very irregular doing it, showing quite a bit of "cogging".

If this sounds familiar, double check all the connectors in your wiring..... make sure a terminal is not crimped onto insulation instead of a wire, etc, etc.

See if you can test a different motor on that same VFD with the same wires.

AiR_GuNNeR
05-09-2010, 05:24 AM
Thanks Tiers,
This is a 6 wire European unit, There are two bundles of three wires coming out and all have connectors on them.

If it was single phasing, would it start right up when connected to the RPC? There was no hesitation or anything. I did have a different 3hp motor that I hooked up to the VFD, and it spun up smoothly.

J Tiers
05-09-2010, 09:17 AM
Thanks Tiers,
This is a 6 wire European unit, There are two bundles of three wires coming out and all have connectors on them.

If it was single phasing, would it start right up when connected to the RPC? There was no hesitation or anything. I did have a different 3hp motor that I hooked up to the VFD, and it spun up smoothly.

I know what the motor *is* from the pictures. Two of the test motors we use are also that type.

The "single phasing" would NOT be INSIDE the motor..... your test proves the motor is fine.

No, the RPC would not start a defective motor any better than the VFD, almost surely. What I suspect is a fault in the wiring, or possibly a fault in the VFD or its programming.

There MIGHT be a problem with a connector in the motor, and you just happened to bump the wires/connections the right way when hooking up the RPC.... unlikely, but possible.

bad grammar edited out