PDA

View Full Version : Why does your housing society pump consume less and less current after running.


Rainbowinthesky
Nov 19, 2013, 12:15 AM
Why does your housing society pump consume less and less current after running - Its rating is 9 Amp it starts with 6.4 reducing slowly to 5 Amp?

smoothy
Nov 19, 2013, 06:11 AM
All electric motors have a inrush of current at startup in excess of what it takes to continue running. There are a number of reasons for this some of them requiring an in depth knowledge of physics and electricity.

But a simplified answer is it takes more energy to get an object started into motion from being at rest... than to maintain that motion once started.

ma0641
Nov 19, 2013, 07:42 AM
Smoothys simple explanation is also a simple explanation of Newton's First Law. Because of inertia it takes more energy to get started than to keep running.

hkstroud
Nov 19, 2013, 08:15 AM
Agree with the previous explanations plus the fact that the start windings of the motor as well as the run windings are energized during start up. After reaching approximately 75% of run speed, the start windings are de-energised.