Steep fronted surges applied to large AC motors-effect of surgecapacitor value and lead length

The line end coil of large AC motors is known to suffer increased inter-turn voltage stress under steep fronted surge conditions. Surge capacitors can be used to slow down the surge rise-time. The effects of capacitor value and lead length on the line end coil voltage are examined. The theoretical and measured waveforms for the line end coil of a 3.3 kV, 1 MW, four-pole induction motor are compared. The results show clearly that when the capacitor lead length approaches 1, even a relatively large capacitor value has little effect