Single to three phase inverters

[BQW]

Can some one explaine this, a friend of mine has a 3 phase lath in his workshop connected to a single to 3 phase inverter, he has trouble with the lathe motor phaseing at slow speeds and when reversing, he read in a engineering magazine that if you connected another small "slave" motor across the inverter output it prevents this problem.
I assume the out put from the inverter is not sinusidel hence the phaseing but why does putting another small inductive load across alter things ?

 

[Stoday]

If you read the invertor instructions you are likely to find that it must supply a minimum current. If the normally connected load can fall below this threshold, you need to add a small load. This can be in the form of a resistor (3-phase, of course) and does not need to be inductive.

You do need to read the manufacturer's manual.

 

[BQW]

Many hanks for the reply, it does make sense what you say, and I suppose a motor would be the easy way to do it.

 

[bigvern10]

Hi BandQwanker!

I'm a little bemused by the answer to your problem. Connecting another motor in parallel with the output from an inverter to cure a fault...??? Never heard of it! What exactly does "lathe motor phaseing at slow speeds" mean? Phasing how? Runs lumpy? Stalls easily? Motor 'vibrates' but doesn't turn?

An inverter should be able to run a motor at all frequencies irrespective of load (provided it's the correct rating), though the motor relies on running at it's design frequency for cooling so running at slow speeds for an extended period may cause overheating.

Suggest to your friend to try altering the TORQUE BOOST setting of the inverter to give greater stability at slow speeds.