since the e.m.f Ep behind the stator leakage reactance at zero power factor overexcited is greater than it is at higher power factors for the same terminal voltage and stator current, the test terminal voltage may be reduced to a value which results in the same value of Ep as that at rated load. the resulting stator temperature rise Δθ can then be measured and used as an indication of the rise that would occur at rated load.