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Chaz
29-11-2015, 05:28 PM
Not sure where to post this.

I bought a Becker VT 4.25 Vacuum pump on ebay as it was 'faulty'. This is to 'power' my vacuum table.

I was hoping that it was not really faulty and that I may be able to repair it. I didnt pay much for it, so worth a chance. The machine came without the faceplate but following the manual below, its a 3 phase motor that can be run using single phase. The motor is 0.9KW or around 1.1HP.

http://www.ecovac.com.tw/pdf/rotary_vane_pumps_%20oil-free/operating_instructions/oi_vt4.25.pdf

After messing around with starting capacitors, I manage to get the machine to spin up. It runs up to full speed however whenever I add any load, the machine stalls. I found that the wiring wasnt 100%, so I rearrange the wiring. I measure around 6.7 Ohms across 3 distinct coils which seems to imply that the motor is fine.

So, as the motor cannot take much load before it stalls, is it faulty? Could it be too large to run on single phase (Im using a starting cap, no running cap and it stays in circuit all the time, no logic to remove it from the circuit).

Im tempted to buy a 4KW spindle and VFD although I dont strictly need it. The VFD could be used to see if the motor works on 3 Phase. These pumps are expensive and if it works for my vacuum table, it will be a bargain.

Thoughts?

Thanks

uli12us
29-11-2015, 08:36 PM
If you start the motor without load you need only a running cap, it should be in the range of 35F. But without running cap, the motor can't run. But you must run the motor in triangle instead of star connection.
Instead that you can use a VFD, but this part is much more expensive.

Chaz
29-11-2015, 08:48 PM
If you start the motor without load you need only a running cap, it should be in the range of 35F. But without running cap, the motor can't run. But you must run the motor in triangle instead of star connection.
Instead that you can use a VFD, but this part is much more expensive.

So I can get it to run with a starting cap. It goes up to what sounds like full speed but has no torque. This does sound like a common issue with a 3phase motor 'single phases'.

Chaz
29-11-2015, 09:41 PM
If you start the motor without load you need only a running cap, it should be in the range of 35F. But without running cap, the motor can't run. But you must run the motor in triangle instead of star connection.
Instead that you can use a VFD, but this part is much more expensive.

Are you saying it should run in Delta with a 35 uF cap for starting?

Clive S
29-11-2015, 10:12 PM
Chaz There is a drawing on the pdf you linked to with a cap does it say the value of the cap? How exactly do you have it connected.

Chaz
29-11-2015, 10:15 PM
Chaz There is a drawing on the pdf you linked to with a cap does it say the value of the cap? How exactly do you have it connected.

Nope, no value.

I dont have the nameplate either.

The guy at Becker UK told me these motors cant be run single phase. Odd, the drawing shows it can or should be possible. Unless there is a 3 phase and single phase version which is different.

Clive S
29-11-2015, 11:36 PM
Nope, no value.

I dont have the nameplate either.

The guy at Becker UK told me these motors cant be run single phase. Odd, the drawing shows it can or should be possible. Unless there is a 3 phase and single phase version which is different.
OK Have you wired it the same as the plate on the motor

Chaz
30-11-2015, 07:27 AM
OK Have you wired it the same as the plate on the motor

The motor didnt come with a name plate.

Im fairly sure its a 3phase motor, not 'made' for single phase.

Clive S
30-11-2015, 09:38 AM
The motor didnt come with a name plate.

Im fairly sure its a 3phase motor, not 'made' for single phase.
OK But are the terminals laid out like in the 1ph picture on the pdf with links in. and can you see 6 wires from the coils connected to them?

Chaz
30-11-2015, 10:13 AM
OK But are the terminals laid out like in the 1ph picture on the pdf with links in. and can you see 6 wires from the coils connected to them?

The wiring was a Star connected 6 wire system. That said, when I checked the pattern, it didnt match the drawing in the document, someone could have messed with it.

Ill try delta connection tonight and see if that helps before considering buying a VFD (120 ish for a 4KW unit that can run the 4KW spindle later).

uli12us
30-11-2015, 11:07 AM
If you can use a 4kw VFD then you have a 3~ mains. A normal 1~VFD have a maximum of 2,2kW.
Thats the maximum, what your 13Amp power socket is capable. The VFD can have more power then the motor, but should be in a similiar power range, 1,5 to 2 * the Motor is ok but not 5 times.

Chaz
30-11-2015, 11:09 AM
If you can use a 4kw VFD then you have a 3~ mains. A normal 1~VFD have a maximum of 2,2kW.
Thats the maximum, what your 13Amp power socket is capable. The VFD can have more power then the motor, but should be in a similiar power range, 1,5 to 2 * the Motor is ok but not 5 times.

Thanks. Understood. I am running my mill from a 32A socket.

Chaz
30-11-2015, 10:26 PM
So, wired to Delta. 30uF cap, doesnt spin up, just turns slowly.

Connect a 300uF cap, instant spin up. Takes full load, can block the vacuum pipe with my hand, it just keeps going.

The only thing was that motor got hot very quickly. I didnt have the cowl structure on it so that meant no real cooling. It got hot very quickly however.