Motor Size

From Imrtwiki

Noel from Blue Circle has had good experiences with his motor reliability and attributes this to specifying motor size one up from suppliers rating. He indicated that this approach minimizes overheating problems that can occur with running motor at there rated maximum power.

Chris from Hunter Water suggested that the way to achieve operating temperature reductions is to specify Class B for temperature increase and Class H for insulation. He indicated that modern insulation can run consistently at high temperature and so the standard motor rated power outputs are for operation at these high temperatures. The Class B temperature increase limits the maximum operational temperature and will allow a motor to remain in-service for 20 years rather than 5 year average winding life with high operating temperatures. Chris suggested that motor efficiency does not tend to drop until motors run below 75% of the rated load. He suggested you should be careful where plant is designed for minimum installed cost such as for shorter term build and operate contracts unless these contracts are for a 20 year period.