Question

A 5 HP, 3 phase, 400v star connected squirrel cage induction motor meant to drive a milling machine. At starting, the machine takes the current about______​

Answer 1

Given :

The power of 3 -phase squirrel cage induction motor = 5 HP

The supplied voltage = 400 v

To Find :

The current that machine would take

Solution :

Let The rating of current = I amp

∵  For 3-phase induction motor

 Power = $\sqrt{3}$ $V_L$ $I_L$ cos∅

power factor rating of I M , i.e cos∅ = 0.85

i.e Power = $\sqrt{3}$ × 400 × $I_L$ × 0.85

Or,  5 × 746 = $\sqrt{3}$ × 400 × $I_L$ × 0.85                        ( ∵ 1 HP = 746 watts )

Or,  3730 = 588.88 × $I_L$

∴      $I_L$  = $\dfrac{3730}{588.88}$

i.e Line current =  $I_L$ = 6.33   Amp

Hence , The Line current of Induction motor at starting is 6.33 Amp   Answer