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Electric Motors/Lathe machine not working, electric motor OK


lathe machine on board my ship is not working. it has a 440V motor which is checked and OK. The control power is 24V AC. The fuses and components are checked and seems to be OK. I dont have a drawing onboard. Can you please tell me how to solve the problem? I even checked the continuity of the contactor coils also.(5-6Ohms). Please help me.

440 volt three phase motor with 24 volt control circuit,   who checked motor?   Is motor just not coming on?      When you engage starter is there voltage at motor junction box?

Does it hum or just nothing?

Do you have 24 volts at the coil?

Can you manually push in motor contactor      if so what happens,     ??

What is the voltage if three phase    Line to line to line    before or on the non load side?

Often these general questions if it is three phase,    is a result of the incoming three phase power either single phased   [one leg dead]  or browned out   [huge unbalance of supply voltage,     

I take it the power comes from a generator either dedicated or shared,    I would make sure the incoming power is there,   first,      if it is just a part of a grid off a gen,  then find out where the incoming voltage comes from  and check it,          

Explain not working,       in detail,        any history of failures on this machine?   Anything happen that was noticed before it failed?

Basically you have incoming power,   two legs are tapped and transformed to control voltage which feeds contactor coils,    and other controls,       

If one leg opens   it could be the leg that provides control voltage,    

LOOK FOR THE SIMPLE STUFF FIRST,   90% of the time  we all figure it is something complex  when it is just a down stream fuse,       once you prove voltage is good  and balanced,   and THERE,        then it is either a bad contactor    loose wire,     so on,   once the contactor closes and voltage passes through   if the motor is good, it should run,   is there interlocks, safety  anything like that?

You say fuses and components  SEEM to be OK   what does SEEM mean?  Fuses are good or not,   are they loose,  is a wire loose,   do you have a non  contact voltage tracer?   You should have on a Ship,     follow the beeps until the pen stops beeping and then you found the open,     if not use your VOM and do it the old fashioned way,      

Take motor connections loose,    put your volt meter on the feed leads,   what is the open circuit voltage at the motor   [I know it is a hassle but you can take a sharp probe and stab each leg     to save un taping   the connections,          recheck the connections,      is the motor wired correctly?   Does it have an internal thermal in the motor  in series with the starter coil?    Sometimes there are klixons at line voltage that simply get hot and open up,   or it could be a thermistor,    but that would be elaborate for a lathe motor,      but is there any KIND of thermal  anywhere?

How about the reversing switch?   Anything open in there?

Check the simple stuff again,    SEEMS   is not a good word,    you can check the fuses with a meter powered on   but be careful,  or else   shut it down pull the fuse  and check each one on a bench,    look for corrosion anywhere and everywhere,   it takes nothing to create a high resistance connection from water or high humidity,     and being on a ship,   I know that is a constant problem,  

Remove anything suspicious  and bench test it,       I need more info,   who checked motor and how,?   There are only a few external tests for a motor,  megger to ground,  check for continuity between leads,       check voltage at motor,         with probes,  or  un tape and measure  LINE TO LINE TO LINE       if three phase   I dont care what line to ground is,      I do care what the overall winding insulation value is,          

more history,   maybe some photos,

My shop is MEAR Services Inc,    Kansas City Missouri,,  phone number to shop   816-650-4030     or you can write to my personal e-mail at   if easier for you,        we are central time US,  

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Three phase/ AC DC single phase motors, controls, any problems or failures, motor installation, performance issues, connections. All other electric motors/gearboxes/apparatus. Specialty repair concerns, obsolete motors and solutions. Other mechanical or specialty equipment. See my profile under Home/electrical at this site


30 plus years in the electrical motor and apparatus repair industry. VP level management of repair facilities, current owner of my own specialty repair and consulting firm.

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