
AC and DC Motors 125
Example 5.9
A 3-phase, 460 V, 60 Hz induction motor with a Δ-connected stator is designed
to have the magnetic flux density in the core at the saturation limit of 1.6 T. If this
machine is connected to 50 Hz lines, determine the voltage for limiting the flux
density to the same 1.6 T saturation limit.
SOLUTION
Each phase of the Δ-connected stator sees the line voltage.
Using Equation (3.2) at 60 Hz, we have V
60Hz
= 460 = 4.444 × 60 × N × ϕ
m
.
At 50 Hz, we have V
50Hz
= 4.444 × 50 × N × ϕ
m
.
Taking the ratio of the two with the same number of turns N and to keep the
same flux ϕ
m
, we have V
50Hz
/460 = 50/60 = 0.8333, or V
50Hz
= 0.8333 ...