lathe starting load

[msn_jrd]

Im looking at manufactured RPCs and on starting load charts like easy, medium, and hard starts they have lathes as hard starts and was wondering if a large lathe with a clutch would be still be considered a hard start? Seems like with the motor starting with the clutch disengaged it would be an unloaded start?

[Geof]

I see nothing wrong with your logic. If the clutch is disengaged when the motor starts it is an unloaded start. You must have a manual lathe with a clutch. In my experience this is not very common which could be why the RPC companies list lathes as a hard start.

[msn_jrd]

oh really im no machinist so i haven't been around very many different machines so i figured this was normal it would be nice if it is an easy start

[hareng]

Its still regarded as a hard start up to three times the motor rating.
ie a 3hp can be like starting a 9hp.

I do have a 240V single ph 1 1/2hp lathe with a clutch, blows a 13A fuse 1 in every three startups.
Likewise the other lathe M300 with 3hp 3ph 400V needs a 10HP inverter. A 5.5hp inverter lasted 1 1/4hrs that could supposedly handle 150% of rating for 30 secs.

[Al_The_Man]

If it is just one dedicated machine, have you considered a VFD?
Al.

[ericsuarez]

Alguien repara driver de spindle y servo motores

[mike_Kilroy]

Originally Posted by hareng .........Likewise the other lathe M300 with 3hp 3ph 400V needs a 10HP inverter. A 5.5hp inverter lasted 1 1/4hrs that could supposedly handle 150% of rating for 30 secs.

It would be good to list for us all what BRAND 5.5hp vfd only lasted 1.5hrs on a 3ph 400v 3hp motor..... I assume it was powered from 400v 1ph input?

Obviously this is not right and we would all like to know the brand for our own reference......

hope u returned it and got a full refund....

[hareng]

The difference is though Mike it was wired plug and play, not direct to the motor with no controls which it was quite happy doing on a 3 sec soft start.
Teco MA7200

Now running the MA7200 7.5kw plug and play via the contactors.