Section 15.4: Performance Calculations cont.

Example 15.2 cont.

Then the air-gap power is:

Pg = Pin - |Is|2Rs = 3.58 KW - (30A.)2 ´ 0.2W = 3.4 KW

The developed power is:

Pd = (1 - s)Pg = (1 - 0.025) ´ 3.4 KW = 3.315 KW (per phase)

The per-phase average output power is:

Pout = Pd - Ploss = 3.315 KW - 350W./3 = 3.198 KW (per phase)

n = (1 - s)ns = (1 - 0.025)´(120´60Hz/4poles) = 0.975´1800RPM = 1755 RPM

\ wm = 1755 RPM ´ (2p rad./rev.) ´ (1 min. / 60 sec.) » 184 rad./sec

Ergo, the output torque is:

Tout = 3Pout/wm = 3 ´ (3.198 KW) / (184 rad./sec.) » 52 Nt×m

And the efficiency is:

Pout/Pin ´ 100% = 3.198 KW / 3.58 KW ´ 100% » 89.3%