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ml018
29th Jul 2018, 03:57 PM
Hi,

I am restoring an old drill press which has an inbuilt 3 phase motor.
There are only 3 leads which makes me believe it's a star connection.
The resistance between each of the wires is 17.4 ohms.

For a test, I connected it to a VFD, but it only hums and makes a sort of grinding noise, but does not turn.
I've swapped the cables around multiple times but the problem persists.

Anyone have an Idea what could be causing the problem?
Does there need to be some fuse or breaker?

LexD
29th Jul 2018, 04:05 PM
What frequency have you got the VFD set to?

BobL
29th Jul 2018, 04:23 PM
I agree the frequency may just be too low

Is the belt connected? if so remove the belt and try again.
The belt alone could be enough to prevent a is 415V motor starting under 240V 3P.

BTW 3 wires means it could still be a delta motor.

LexD
29th Jul 2018, 04:47 PM
When I set up a new Chinese VFD on my surface grinder I did not check the Maximum Frequency setting because I was in a hurry to see it go for the first time, the motor just sat there making funny noises until I realized that the drive was set to 400Hz, after resetting to around 60Hz it started and ran perfectly.

BobL
29th Jul 2018, 06:03 PM
When connected to a 50Hz motor a Huanyang VFD with a 10s acc time and a 400Hz max will start the motor but switch it off at about 200Hz and report an error.

ml018
29th Jul 2018, 08:46 PM
The motor stator had a stamp 40-60 Hz 415v.
How can I check the frequency which my VFD is running off (currently turning the little pot gives values from approximately 0-60)?
A different motor will run just fine from the same VFD.
This drill press is geared, where the entire motor is built into the casting and can be removed.

BaronJ
29th Jul 2018, 09:41 PM
Hi Mlo18,

I think that you need to carefully, physically check the motor windings for any damage ! Better yet take it to a motor re-winder and let them cast an eye over it.

LexD
29th Jul 2018, 09:43 PM
Is your motor two speed? How many horsepower? What size drive?

ml018
29th Jul 2018, 09:56 PM
This is the VFD i currently have from ebay: 1,5 KW 3 Phase VFD 220V
I am not aware of what the HP of the motor is. I will check if the manufacturer of the drill press put the information somewhere.
I was able to completely remove the stator, I did not see any damage, it looked very good.

Bear with me, I am still learning.

BobL
29th Jul 2018, 10:00 PM
Are you connecting the VFD direct to the motor.
If you have any sort of switch like contactor in the way this is A) not good for the VFD and B) will not work

ml018
29th Jul 2018, 11:55 PM
Are you connecting the VFD direct to the motor.
If you have any sort of switch like contactor in the way this is A) not good for the VFD and B) will not work

The VFD is connected directly to the motor.

BobL
30th Jul 2018, 12:42 AM
The motor stator had a stamp 40-60 Hz 415v.
How can I check the frequency which my VFD is running off (currently turning the little pot gives values from approximately 0-60)?
A different motor will run just fine from the same VFD.
This drill press is geared, where the entire motor is built into the casting and can be removed.

Can you turn the gears/motor by hand - it's not locked at the spindle or elsewhere in the gear train by chance?

benhoskin
31st Jul 2018, 12:15 AM
I suspect you have a 415 volt motor in its current setup, It maybe possible to change but expect some work. The load from the gear train might be enough to stop it when you are feeding it 220v 3phase.

ml018
31st Jul 2018, 02:43 PM
The motor spins freely even with the gear setup. I have removed all the gears, the motor makes vibrating noises and is hard to turn by hand when the VFD is switched on.
On one side the motor is easier to turn, then had a sudden jump before stopping again (wrong phases connected?).

BobL
31st Jul 2018, 03:27 PM
The motor spins freely even with the gear setup. I have removed all the gears, the motor makes vibrating noises and is hard to turn by hand when the VFD is switched on.
On one side the motor is easier to turn, then had a sudden jump before stopping again (wrong phases connected?).

Not phases so much but coils themselves maybe connected incorrectly.

Has the motor ever run correctly to your knowledge?
Is there evidence that someone has messed about with the wiring inside the motor end cap - can you open the endcap up and take a photo?

ml018
31st Jul 2018, 04:10 PM
Not phases so much but coils themselves maybe connected incorrectly.

Has the motor ever run correctly to your knowledge?
Is there evidence that someone has messed about with the wiring inside the motor end cap - can you open the endcap up and take a photo?

The people I bought the drill from told me it worked, but I they never turned it on.
The entire stator can be removed from the casting by loosening two grub screws.
the rotor spins freely withing the stator.
The resistance readings from the multi meter all came up with 17.4 ohms between the coils.

BobL
31st Jul 2018, 04:36 PM
The people I bought the drill from told me it worked, but I they never turned it on.
The entire stator can be removed from the casting by loosening two grub screws.
the rotor spins freely withing the stator.
The resistance readings from the multi meter all came up with 17.4 ohms between the coils.

Each coil (1, 2, 3) has two ends (A and B)

In Y connection all the B's are connected forming the common point - the Phases are then connected to the A's in any order.

In the ∆ connection 1B is connected to 2A, 2B to 3A, and 3B to 1A.

If a consistence is not maintained so that an A and B are mixed up on one coil this will cause the problems you describe.

ml018
2nd Aug 2018, 05:11 PM
Each coil (1, 2, 3) has two ends (A and B)

In Y connection all the B's are connected forming the common point - the Phases are then connected to the A's in any order.

In the ∆ connection 1B is connected to 2A, 2B to 3A, and 3B to 1A.

If a consistence is not maintained so that an A and B are mixed up on one coil this will cause the problems you describe.

I tried connecting the motor to the inverter: UVW UWV, VUW, VWU, WUV, WVU.
The motor still refused to turn.
When I turn up the VFD, it makes this sort of accelerating sound but nothing turns.

BobL
2nd Aug 2018, 06:55 PM
I tried connecting the motor to the inverter: UVW UWV, VUW, VWU, WUV, WVU.

All you are doing there is switching the phases which won't make any difference


When I turn up the VFD, it makes this sort of accelerating sound but nothing turns.
Are you starting the VFD at zero Hz? If so then nothing you have said surprises me.

Because I don't know what sort of VFD you have I can only say that the following is safe with a Powtran.
It assumes the max frequency is 50Hz and the current max has been set in the VFD to suit the motor
With a Powtran, with the power off, turn the VFD up to max Frequency.
Set the acceleration time to 3s and push start/fwd and let the VFD take care of it - if it overloads the VFD will not start and will not damage anything.
On other VFDs they usually report a error.

LexD
2nd Aug 2018, 07:37 PM
OK, a couple more questions, what size motor are you trying to drive with the 1.5kw VFD?
Have you tried to start the motor with the gearbox in the neutral position?
What make is the machine, can you post a photo of it?

ml018
2nd Aug 2018, 08:46 PM
All you are doing there is switching the phases which won't make any difference


Are you starting the VFD at zero Hz? If so then nothing you have said surprises me.

Because I don't know what sort of VFD you have I can only say that the following is safe with a Powtran.
It assumes the max frequency is 50Hz and the current max has been set in the VFD to suit the motor
With a Powtran, with the power off, turn the VFD up to max Frequency.
Set the acceleration time to 3s and push start/fwd and let the VFD take care of it - if it overloads the VFD will not start and will not damage anything.
On other VFDs they usually report a error.

Ok, I turned off the VFD and turned the pot to 60Hz position. I turned it back on and started the motor but it still just makes that buzzing noise and wont turn (it cannot be moved the slightest bit when the VFD is powering the motor (not safe I know).
How is acceleration generally set on a VFD (how is the option accessed)?
I know it most likely won't be the same as your VFD, but sometimes Chinese knockoffs are really similar.

ml018
2nd Aug 2018, 08:48 PM
OK, a couple more questions, what size motor are you trying to drive with the 1.5kw VFD?
Have you tried to start the motor with the gearbox in the neutral position?
What make is the machine, can you post a photo of it?

374512
I will take some pictures of the actuall machine tomorrow. I managed to find an advertisement from the 1950's of the machine. I have removed the gearbox completely.

russ57
2nd Aug 2018, 09:29 PM
The motor spins freely even with the gear setup. I have removed all the gears, the motor makes vibrating noises and is hard to turn by hand when the VFD is switched on.
On one side the motor is easier to turn, then had a sudden jump before stopping again (wrong phases connected?).

What do you mean here? Do you mean lying the motor on one side then 'turning it over'? What happens if the motor is vertical.

I'm wondering if the motor is 'poling' - worn bearings letting the rotor touch the stator. With power applied you get attraction, touching and then locking.



Russ

ml018
2nd Aug 2018, 09:57 PM
What do you mean here? Do you mean lying the motor on one side then 'turning it over'? What happens if the motor is vertical.

I'm wondering if the motor is 'poling' - worn bearings letting the rotor touch the stator. With power applied you get attraction, touching and then locking.



Russ

The motor assembly is mounted into the drill casting. It is in a vertical position, when there is no power applied to the motor, it rotates freely with and without the gearbox.
I will take apart the assembly and take pictures tomorrow.
I am starting to think that it may be locking due to the rotor and stator touching like you mentioned as I noticed there is a moment when the rotor turns about 60 degrees and halts.

ml018
4th Aug 2018, 04:29 PM
Problem solved!
It was the rotor all along.
I put the rotor into my lathe and turned down the surface just enough to remove any minute inconsistencies (dings, etc).
Now the motor fires up as it should.