L5 issue

[Neil TaylorParticipant @neiltaylor16781]

Hi all

im sorry to bother everyone but I have a l5 with a three phase motor and a 3 to 1 transformer, when i turn it on the lathe makes a chattering noise and doesn’t stay on for long, does anyone have any advise, I hope this is ok to post here

all the best to you all

[John HaineParticipant @johnhaine32865]

What do you mean by a 3:1 transformer?

[Neil TaylorParticipant @neiltaylor16781]

Hi again

sorry to clarify it’s a Clarke pc60 3 phase converter

regards

[Clive FosterParticipant @clivefoster55965]

Chattering noise followed by stopping is generally due to insufficient voltage on the operating coils of the contactor switching the motor on and off making it unable to stay in the “ON” state.

Best practice is to run the control gear off the 240 volt mains feed. The third, wild or generated, leg is somewhat unstable and doesn’t exist until the more is turning.

Worth verifying that your contactor does have a 240 volt coil.

I presume you have converted the motor internal connection from star (Y) to delta so it will run properly off the 240 volt converter output.

Clive

[Neil Taylor]

On 19 December 2024 at 13:31 Neil Taylor Said:

Hi all

im sorry to bother everyone but I have a l5 with a three phase motor and a 3 to 1 transformer, when i turn it on the lathe makes a chattering noise and doesn’t stay on for long, does anyone have any advise, I hope this is ok to post here

all the best to you all

Hi Neil. Fine to post here.

1. Has the Lathe has run OK on the static convertor for yonks, and then suddenly failed. Or
2. This is a new installation that’s never worked properly?

Case 1 suggests the static converter is sick.  Often due to capacitor failure – they can be replaced.

Case 2 suggests the static converter is unsuitable (maybe too small), or otherwise not a good match to an L5.  I don’t know what an L5 needs and hope a few owners will comment.  Static converters are a bit of an electrical bodge, and don’t play nicely with all machines.

Dave

[Neil TaylorParticipant @neiltaylor16781]

Hi clive

thank you for your reply I will pass this on to my friend who is a sparky regarding what you said

thanks again

[Neil TaylorParticipant @neiltaylor16781]

Hi dave

this is a new setup so I have no older information, thank you for your reply

[Pete RimmerParticipant @peterimmer30576]

Check that the lathe’s control circuit is not fed from the generated phase. what you’re experiencing is a common symptom of that.

[Neil TaylorParticipant @neiltaylor16781]

Hi Pete

I will pass this on thank you for your reply

[Neil TaylorParticipant @neiltaylor16781]

Hi Pete

to rectify this problem can I swap any of the lives in the plug over? Sorry if this is a stupid question but I don’t know

thank you for your response

[EmgeeParticipant @emgee]

As said above you need to ensure in the lathe starter the coil circuit is across the 400/415V legs, the wild leg will not operate the coil.

Emgee

 

[old martParticipant @oldmart]

Not knowing much about the subject, but as the build id new, could the motor be wired star when it should be delta?

[Nigel Graham 2Participant @nigelgraham2]

That does all seem an electrical problem, not the fault of the lathe, though that needs a reasonably powerful motor.

Mine is happy (so am I as its operator) with a Newton-Tesla 3ph conversion using a 1HP motor, though I don’t try, and don’t need try, running it flat-out.

[Chris CrewParticipant @chriscrew66644]

This sounds like the same sort of problem I had with a cylindrical grinder. The load was too much for the artificial 3-phase supply even though the rating of the converter appeared adequate. If there are two belts on a double pulley try removing one of them as they may be working against each other if they are not matched. Try starting the lathe in its lowest gear to minimise the torque needed to get it running. If the motor runs with little or no load, it’s down to the converter.

[larry phelan 1Participant @larryphelan1]

Just my pennyworth,

That is a serious machine, I,m surprised it has only a 1 hp motor.

As others have said, it might be worth checking to see how the motor is wired, and also check if the converter is strong enough. I had a somewhat similar problem some years ago, using a borrowed static converter to run my planer, the machine just laughed at it.

Turned out that the converter was just too small, so I ended up buying a rotary one, problem solved ! The last thing you want is to burn out your starter, so do a check on the motor AND the starter coil, then look at the converter.

Let us know what you find, all info comes in useful.

[ZanParticipant @zan]

I got my L5  a long time back. Ripped out all of the electrics as they were all working at higher voltage than my 240v  inverter   A new box had to be built to replace the original control chassis.  I fitted new contractors   I tend to still use the gears for changing speed with a pot giving a small change to each speed to suit conditions because I recognise the old 3 phase motors can have problems with big variations of Rpm. The motor connections need to be altered for 240 v operation  as mentioned above. A couple of big capacitors were wired up to work the suds feed pump.      I’ve had no problems for 20 years……

[Chris CrewParticipant @chriscrew66644]

“A couple of big capacitors were wired up to work the suds feed pump.      I’ve had no problems for 20 years……”

It’s good that you have had no problem with your suds pump but I did with one on a Student which I was running from a 5HP static Transwave. When I stopped the lathe the suds stopped flowing so I assumed the pump had been switched off along with the main motor but it hadn’t because, upon checking the Colchester wiring diagram, I found that it was connected directly to the ‘unbroken’ side of the contactor. This meant that the pump was still connected to the full output of the converter but was not of a sufficient HP to trip the starting capacitance and keep running so, unbeknown to me, the windings just got silently hotter whilst the lathe was stationary. Eventually a winding burnt out and it cost me a motor rewind. The solution was that I fitted a small auxiliary contactor for the suds pump in parallel with the main one which was a bit ‘belt and braces’ as I could have just as easily connected the pump directly to the ‘broken’ side of the main contactor.

[ZanParticipant @zan]

Ah yes I also put a contractor on it

[Nigel Graham 2Participant @nigelgraham2]

Larry –

Yes, it is a “serious machine” but the motor I replaced on mine was a single-phase 1HP unit, and looked old enough, and was so fitted, to have been original.

Not sure without looking what the makers specified but 1.5 HP would be better. I simply don’t try to work the elderly machine and new electrics at full woof in top gear.

[Howard LewisParticipant @howardlewis46836]

Whatever motor you fit, bear in mind that a single phase motor will not run as smoothly as a three phase, and that it will need to be of higher power.  1/2 hp three phase or 3/4 hp single phase seems to be the norm for smaller hobby lathes.

My Taiwanese lathe would have come with a 2 hp single phase, but a 1.5 hp three phase, driven by a VFD has never been short of power in the twenty years that I’ve had it.

Howard

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