 During a motor start the line voltage drop will fluctuate and the magnetic flux in the hold-in device will also vary, causing deviations in opening times.The change in motor starting current from the reduced voltage stage can be minimised by switching at transition to a primary reactor second starting stage.In his patent Max Korndörfer shows an external reactor coil method "so as to make the gradation in voltage between steps" before a changeover to direct-on-line.