×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Bonding of covers

Bonding of covers

Bonding of covers

(OP)
We have some large motors that have covers over the slip rings, the covers are removable using a standard panel key, should the covers have a bonding wire between the covers and the generator? I know electrical panel doors should be bonded?
If a bonding wire is required what size should it be? the main supply earth is 25mm2 are there any regulations I can look at for this?

RE: Bonding of covers

The generic rule is that "Any conductive part that can get into contact with a lethal voltage during normal operation or any conceivable fault condition shall be permanently and securely connected to a reliable ground".

It is expressed in different ways in different standards. But that is the gist of it. The bonding braid/wire shall have enough capacity to carry the worst case fault current without melting (or getting too hot) until protection trips.

My pet is that a motor shaft needs to be grounded (permanently and securely) if both bearings are insulated or have ceramic balls.

Gunnar Englund
www.gke.org
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

RE: Bonding of covers

To richerdick32 (Electrical)(OP)

In the IEC world, the general opinion and practices are:

A. For motors
Motor slip rings removable covers, cable-box removable covers and the like; the usual [metal screwed connections or clamping force by the metallic locking mechanisms] are (considered sufficient to ensure earthing continuity) [provided that no electrical equipment is attached to them]. No PE-conductor is required to be attached on them.
Note: For conductive parts where no electrical equipment is attached to them; if preferred but not mandatory:
a) may be earthed by a flexible bare conductor or with (transparent) sleeving, or with an insulated colour-coded PE-conductor with colour-code, see detail C below.
b) the PE-conductor, bare or insulated shall be NOT smaller than 2.5sqmm of copper material. Larger size if aluminium conductor is used.

B. For electrical panels {See IEC 60439)
" For lids, cove plats and the like, the usual screwed connections and metal hingers are considered sufficient to ensure continuity provided that [no electrical equipment is attached to them]"
Note: For conductive parts where electrical equipment [exceeding the limits of extra-low voltage] are attached to them:
a) steps shall be taken to ensure continuity of the protective circuits.
b) the (copper) PE-conductor [shall not be smaller than 2.5sqmm] but [need not be larger than the largest wire size wired on the equipment] attached on them.

C. PE-conductor colour-code per IEC
a) PE-conductor may be
- bare (no painting of colour is required),
- bare with (transparent)sleeving,
- insulated with colour-coded "yellow/green"
Attention:1. Except "yellow/green" coloured-coded insulated conductor, NO other colour-coded conductors shall be used as PE-conductor.
2. "Yellow/green colour-coded insulated conductor shall NOT be used for phases or neutral conductor.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources