Home » » Single Phasing in AC Motors

Single Phasing in AC Motors



Single Phasing in AC Motors




bullet
The loss of current through one phase of a 3 phase supply is described as single phasing.
bullet
During single phasing no current passes through one line while other two lines carry excess current depending on the load.
bullet
As shown in figure other two lines carry 2.4 times normal line current for the load.
bullet
Also phase current distribution also will be altered.
bullet
Coil 'B' and 'C' carries 1.3 times normal phase current while coil 'A' carries 2.9  times normal phase current. Reason is clear from the diagram itself ( Since current from one phase finds coil 'A' as low resistance path )

 

Causes of Single Phasing

  1. Line fuse blown off
  2. Terminal contacts broken due to vibration or ageing
  3. Terminal contacts become loose
  4. Line wire broken
  5. In contactor relay, one of the contactor is not making proper contact
  6. Relay contact spring may be damage or weak
  7. Contact joints covered with oxidation product, hence not conducting


Effects of Single Phasing
  1. Uneven distribution of current in the motor windings which may damage them
  2. Motor will keep on running with noise and vibration but once stopped, it will not start
  3. Due to uneven distribution of phase current, there will be fluctuation in torque produced
  4. Motor will vibrate vigorously
  5. Fluctuation in motor rpm
  6. Cause humming noise
  7. Motor winding may burn out
  8. Possibility of electrical fire
  9. Winding insulation may melt, causing short circuiting or earthing, results in electric shock and casualty
  10. Generator may overload and associated problems.

Write to me at marinenotes4u@gmail.com,283928@gmail.com.::MK::.
Facebook:Marine NotesTwitter:ACMWCTRss:ACMWCT
Marine Notes - MMD Exams India and Baiscs
URL: HTML link code: BB (forum) link code:
© Marine Notes - MMD Exams India and Basics (M&K Groups Ltd)

0 comments:

Facebook Marine Notes
Twitter Marine Notes
Rss Marine Notes
MMD results india

Followers

Image and video of marinenotes
Marine Notes Help Desk

Archive