3 phase motor issue

[Wendelspanswick]

I bought a used SCM universal woodworking machine and the motors for that were 440/715V rather than the usual 230/440V that we normally get in this country, could be that you have a mis-badged motor intended for a higher line voltage?

[Big J]

It's definitely 400v.

 

Higher motor power would not go amiss, but the Logosol frame saw runs more blades (20) on only 11kw, so this should have no issues on 10 blades with 15kw.

[eggsarascal]

Has it got a speed controller on something like this?

 

https://www.tradepumps.com/hv4055w-variable-speed-pump-inverter?gclid=CO-r7a2N2M0CFQuNGwodjLIHKA

 

Ok, this one is off a pump motor but that doesn't matter.

[openspaceman]

It's definitely 400v.

 

Higher motor power would not go amiss, but the Logosol frame saw runs more blades (20) on only 11kw, so this should have no issues on 10 blades with 15kw.

 

You say it runs 10A on star with no load, which is 2.4kVA then no load on Delta is 13A, which is 5kVA yet the full power load is 15KW at what power factor? At no load the motor speed should approach synchronous and tend to a power factor of one, at full load the drag shouldn't get more than 10% but the power factor will be .7 IIRC from lectures some 45 years ago.

 

If you have a clamp meter on one phase, given the sum of the currents on the other two phases is equal and opposite on a balanced system the I wouldn't expect the no load current to be 30% of the full load current. I'd like to see the current waveform on each phase in real time

[Big J]

You say it runs 10A on star with no load, which is 2.4kVA then no load on Delta is 13A, which is 5kVA yet the full power load is 15KW at what power factor? At no load the motor speed should approach synchronous and tend to a power factor of one, at full load the drag shouldn't get more than 10% but the power factor will be .7 IIRC from lectures some 45 years ago.

 

If you have a clamp meter on one phase, given the sum of the currents on the other two phases is equal and opposite on a balanced system the I wouldn't expect the no load current to be 30% of the full load current. I'd like to see the current waveform on each phase in real time

 

Most of what you have said there is beyond my expertise, but I shall relay it to the more qualified people that are coming to look at it this week!

[Big J]

FIXED! Wooooooo!

 

Many, many thanks to Steve (roys) for being the fresh pair of eyes on the machine.

 

We did the full range of electrical tests again, nothing came up. In the end it came down to belt tension.

 

The first thing I checked when it wasn't running right was the belt tension and it was the first thing I adjusted. I did tighten it a fair bit in the first instance, but clearly not enough. Many, many turns of the tensioning bolt later, it's roaring through the logs.

 

It sounds bloody stupid to have missed it, but over half a dozen of us, mostly more qualified and more experienced with machines than me, didn't pick up on it. Nor did the factory. I just expected the belt tension to be somewhere in the ballpark of correct when it came from the factory.

 

Either way, thanks again to Steve and we're on our way to getting through the 70 odd tonnes waiting to go through it.

 

J

[Marko]

Well done. It's been a good thread to watch with all the suggestions and help that has poured in. Always nice to nail it though; everyone likes a happy ending.

[Big J]

Well done. It's been a good thread to watch with all the suggestions and help that has poured in. Always nice to nail it though; everyone likes a happy ending.

 

A very experienced electrician/woodworker with machine experience friend (who was as stumped as me) said that at least we all learnt something!

 

I feel much more confident on three phase electrics now

[GreenGui]

Excellent news, well done:thumbup: Don't forget to cancel that new motor!!

[Stubby]

Nice one Big J ! Fantastic . Is the new motor still coming ?