Boxford tripping out

[john steel 1Participant @johnsteel1]

I have a boxford lathe which has been working fine. But it now cuts out or trips out. even when not under load pressing the start button makes no differant its dead but next morning it stars normaly

[John Doe 2Participant @johndoe2]

Over current trip or overheat trip ?

 

Can you turn the chuck and gearbox freely, or are they stiff or partially seized ? Might be a bearing binding up somewhere overloading the motor. See if you can run the motor disconnected from the drive-train. And vice versa.

[Speedy Builder5Participant @speedybuilder5]

Also, isolate from the power supply and have a look inside the reversing drum switch.  These get badly burnt up on their contacts especially if (Like me) you use the centre off position to switch the motor on / off.

Also check that your micro switches on the cabinet doors, back gear lever etc work positively.

[noel shelleyParticipant @noelshelley55608]

You don’t say if single or 3phase ? Single phase then Start condenser has gone, it can’t spin up to speed, the start windings stay in and as your lucky to have an overload protector it is cutting out. cools down and resets on start. ONLY to do it again when started ! Check the condenser ( capacitor). Good luck. Noel.

[john steel 1Participant @johnsteel1]

Thank you for your kind replys, Its single Phase, and the chuck turns freely. But will try your replys tomorrow thank you.

[noel shelleyParticipant @noelshelley55608]

Another option is that the centrifugal switch inside the motor has failed to operate – again leaving the start windings in. The momentarty starting surge is one reason a fuse will not protect the motor and an overload device is used – it will take the surge and then start to heat up IF the start current continues eventually and before damage is done it will trip – hopefully saving the motor. They are often adjustable and need to be set to the motors full load amps to work correctly. Noel.

[John Doe 2]

On John Doe 2 Said:

Over current trip or overheat trip ?

 

Can you turn the chuck and gearbox freely, or are they stiff or partially seized ? Might be a bearing binding up somewhere overloading the motor. See if you can run the motor disconnected from the drive-train. And vice versa.

As above plus, some motors also have a bi-metallic switch in them which cuts power when things get really hot. Unlike an overload protector the motor holds the heat for ages.

I had a 3/4hp General Electric motor with one mounted in the end cap along with the centrifugal switch, it cut out after 20 mins running at 60C with a 5C ambient when the motor was sucking 10A+ instead of less than 6A.

If the cold motor starts and spins up normally and the centrifugal can be heard clicking off within a few seconds (you may need to take the belt off to reduce the lathe noise enough to hear it,) then the start circuit would seem OK and it might be winding damage.

Caps tend to show slight bulging or weeping when bad and some motors have a both a start and a run cap to complicate things. The motor plate should have the details on it.

All roads do lead to the motor and these days there are standards for motor mounts, but the shaft size can bring drive pully issues.

 

[john steel 1Participant @johnsteel1]

Just took the switch front off and its a Electronomics 3 phase start and stop switch on the side is a small pointer ahat points to 9.7 12 14.5 its set at 9.7 at the moment. will go back and check the motor it started this morning and ran for 2 min then triped out

[john steel 1Participant @johnsteel1]

Thank you for all your help. I just moved the belt from the left end pullys to the centre pully wheels and it works perfect. so I dont know why it trips when on the large and small wheels at the left end when running with no load free wheeling.

[duncan webster 1Participant @duncanwebster1]

If it trips when the belt is on top speed range it could be motor inrush current issue. It takes longer to accelerate to full speed when on top range. Try it without the chuck.

[Speedy Builder5Participant @speedybuilder5]

I have the same lathe with a 3/4 Hp single phase cap start motor and a very heavy chuck(6″ Burnard Griptu). Looks like the same stop start switch. This is supplied from a 40Amp (30 Mili amp) RDC and 32 amp circuit breaker, and not given any problems in the last 20 years (Crossed fingers!).

[Speedy Builder5Participant @speedybuilder5]

Ps:  Mine is set on 7

[duncan webster 1]

On duncan webster 1 Said:

If it trips when the belt is on top speed range it could be motor inrush current issue. It takes longer to accelerate to full speed when on top range. Try it without the chuck.

Should have read previous posts, if it runs for 2 minutes it’s not the inrush current.

[Dave HalfordParticipant @davehalford22513]

John,

Do you here a click when the motor speeds up and slows down?

[noel shelleyParticipant @noelshelley55608]

The current setting at 9.7A seems high ! If set to high it will offer little or no protection to the motor.  It seems the motor is being overloaded on the high speed possibly due to incorrect lubricating oil causing drag ? This may not be noticable al slow speed. Noel.

[Author]

Posts