Lathe missing required protection?

[Ole electric]

Hi all,

Thinking something may be amiss with this machine installation, please comment.

A old 2 hp 3 phase lathe is fed from a 20 amp 480V branch circuit breaker with a 14KAIR.

There is no motor starter and the drum switch (to reverse rotation) is rated for use on a circuit capable of delivering no more than 5000 amps RMS.

Minimum cost effective remedy? 3 phase fused disc and motor starter?

The last drum switch faulted and melted off when a contact finger broke off from wear. Very exciting!

Ole Electric

 

[Ole electric]

forgot to mention, means of disconnect is a twist-lock drop

 

[jim dungar]

Hi all,

Thinking something may be amiss with this machine installation, please comment.

A old 2 hp 3 phase lathe is fed from a 20 amp 480V branch circuit breaker with a 14KAIR.

There is no motor starter and the drum switch (to reverse rotation) is rated for use on a circuit capable of delivering no more than 5000 amps RMS.

Minimum cost effective remedy? 3 phase fused disc and motor starter?

The last drum switch faulted and melted off when a contact finger broke off from wear. Very exciting!

Ole Electric

The fault current rating of the breaker has nothing to do with the rating of the drum switch.
What is important is finding out how much fault current actually exists.
You may be solving a problem that does not exist.

Your post says the drum switch failed due to wear. Drum switches usually have reduced life in plugging (rapid switching of directions while the motor is still turning) applications.

 

[tom baker]

You need motor overload protection and branch circuit, short circuit and ground fault protection.

 

[stew]

Ground fault protection?

 

[ActionDave]

Ground fault protection?

Yes, ground fault as in short circuit/ground fault protection, not GFCI protection if that is what you are thinking of.