Earthing In Motor Terminal & Body

It is conceivable that the terminal box might work loose from vibration. But then, either earthing connection could also work loose. Maybe there should be 6 earthing connections, in case 5 of them work loose. Isn't contingency analysis fun?

redundancy just might save your life

Go back to the person who asked you, and ask "why?".

Or just do it and move on to something more productive.
Del

Good point.

The feeder cable ground is there to protect equipment & personnel from exposure to an electrical ground fault in the cable between the switchgear and motor and also to provide an alternate path for the equipment ground.

The equipment ground (motor body) is there to protect equipment & personnel from exposure to an electrical fault in/at the motor and/or the equipment the motor is attached to.

If the cable ground is damaged or severed, and the equipment ground is intact and functional, the motor as well as whatever it is attached to will still have ground fault protection and personnel will also be protected.

Since you don't know why, how can you speculate about why not.

Just do it!

The answer was in your question. The motor terminal box and motor body are mechanically connected.

The bonding is the electrical connection.

Is the terminal box insulated with a rubber gasket? Best to have as many earthings as you can to keep everyone safe.

Dear Mohsin,

Your question is relevant. The terminal box you earthed is fixed to body through bolts and has a gasket in between. The gasket is basically provided to make it environmentally protective and proper packing ... but this is electrical insulator. As far as bolts are concerned they may be 4-6 in number but are made of high resistance material normally. Therefore the earthing is demanded on motor body. I don't understand requirement of earthing on both sides of the body... One side .. I can understand. If there are items connected with screws and bolts on either side don't earth them, earth main motor body at the provision made and you may provide a copper strip/wire jumper to bolted parts. This meets Indian standard. You may check for standards if you are elsewhere. I am sure you will certainly agree that a human life saved is much -more costly and valuable than a motor and its earthings.