3 phase cross cut saw problems

[sparkyork]

hi all, a mate of mine is having some problems with the above saw within his workshop. symptoms of the saw are: apparantely all intermitent! 1, blade just rocks and doesnt spin in either direction 2, sometimes motor just buzz's 3, sometimes starts in reverse and stops and starts spinning forward 4, sometimes spins the right way and slowly builds up momentum im relatavely stumped on this, not checked the wiring tho, any ideas anyone cheers

 

[benji]

loose connections /contacts definately in need of thorough strip down/maintenance, this saw is unsafe

yours benji

 

[Darkwood]

Sounds like a phase missing which could be anywhere from a bad connection in the switching to a internal fault on the motor, dont power motor for more than a few seconds or it may burn out. Check for 3 phase at motor terminals when you power it up but as mentioned dont leave power on too long.

 

[boatnik1]

Definately a phase down. First check supply to contactor for 3p ,if ok then disconnect motor supply from contactor and check for 3p out. if still ok then the fault is either connections to motor or there is a phase down in the motor, which could be anything from a broken connection to burned out winding. Remove any links between terminals and check the three windings for resistance, they should be equal. Also check windings to earth for shorts which could knock out a fuse if the supply is fused.

 

[mechelec]

Has it got a dc injection braking that could be causing the problem?

 

[Frenchsparky]

you dentifnealy have bad phase connection so check the phase supply first then the control box.

And the motor junction box { I was going say one word but I feel it is not a correct term unless you are famuair with this one }

and check the setscrew connectors to make sure they are good and tight.

Ring out the cord { megger it } from time to time you may get a break in the conductor as well.

Has it got a dc injection braking that could be causing the problem?

IIRC most case it will useally have interlock device to prevent injecting the DC in the motor as long the motor supply feed is active { alive } plus check the timming device if have it.

somecase they set the timer way too long.

Merci.
Marc

 

[peteludman]

IT SOUNDS LIKE A motor starter capacitor IF THERE IS 1 I HAD A THE SAME PROBLEM

I think im wrong because it was a ac unit i had the problem with

 

[TF and the wire]

If it is 3 phase there won'y be a capacitor, they are only used for single phase motors. I agree that it sound like it is losing one of its phases. There are quite a few places where it could be lost. best to start at the supply and work towards the motor.