Installing and commissioning motors

By H du Preez, Consultant

 

Published in:

Electricity+Control, January 2015 (pages 12 – 15)

Enquiries: Email henry@hdupreez.co.za

 

Read the full article on Installing and commissioning motors in PDF format.

 

A motor frame is generally rigid, but if you place it on an uneven base when bolted down, it can and will twist. The result of this is vibration, rubbing of the seal area in the bearing housing, uneven air-gaps and problems.

‘We just put it on the floor and start it up’ – is sometimes heard and quite often done. Typically, this is how combined units are installed and the user will say: ‘But the motor compressor unit is on a common base’. The user does not realise how this assumption can result in serious electric motor problems and failure.

It has been said that the major causes of electric motor failure are mechanical, and the ‘primary cause’ is often a poor job of installation – especially that the base support is too weak or too flexible. Foundation design and machinery installation require more care than is sometimes practised.

A machine user, if plagued by unexplained bearing failure, high vibration or shaft breakages, can generally assume that the fault lies with poor design and construction of the support structure – foundation, base plate and installation. A poorly designed or badly made motor base, or one that the motor has not properly mounted, too, would lead to premature motor failure.

 

Take note

  • The major causes of electrical motor failure are mechanical.
  • The primary cause is generally poor installation.
  • A poorly designed motor base will lead to premature failure.