Abstract Three phase motor will be burnt out if it starts and works in the absence of phase. So special control circuit should be employed to protect motors, especially motors in pump like diving pump. Motor with this control circuit will never start to work in the absence of phase. Its features are: ①Motor will never start if any one of the phases is absent in the main circuit. ②Current source of main contactor coil is from motor connector, so motor will come to aut stop when any one of the phase is absent. ③Its riability is high.