8 Nov
2016
8 Nov
'16
6:24 p.m.
On 11/08/2016 11:55 AM, Paul Koning wrote:
The
classic formula is 1 hp = 750 W. But there's more to the picture. Motors draw a
steady state current based on the power demanded from them, and the hp rating shows the
max that they are designed for. But when starting they draw much more current.
Well, actually, motors draw a fairly constant current, and
the phase angle between current and the applied voltage
changes with load. At idle, a motor draws almost pure
lagging current (phase almost 90 degrees lagging the
voltage) and at full load the current is nearly in phase
with the voltage. So, the POWER draw changes with load, but
the line current changes much less!
Jon