This paper introduces several proprietary technologies of starter solenoid switch with current-limiting resistance developed by Denso, Valeo, Bosch and the author.

It analyses the performance specialties and the shortcomings of the existing slow-running starters and tells that a totally new double-contact electromagnetic switch with current-limiting resistance can be cooperated with these starters to get the suitable slow-running starters.

A pulsed aging test bench was developad for highvoltage vacuum devices,which was composed of an adjustable high-voltage DC power supply,accumulator,high-voltage pulse transformer,high-voltage switch,trigger,controller,vacuometer,oscillograph,current-limiting resistor,polarity reversing switch,high-voltage breakdown arbiter and high-voltage distributor.

The equipment applied enclosed cycle and current limited to control starting current.

Firstly, the relation between coil turns and minimal starting current is revealed, and the measures to improve the minimal starting current are presented.

The new approach,which checks differential protection connection using electromotor starting current,is simple and reliable,and easy to be coordinated with installation schedule.

The results of theoretical analysis and simulative experiment showed that the method mentioned in paper can accurately distinguish the startup current and the short-circuit current and was simple.

Experimental results show that the scheme can be easily applied to control a three-level pulse width modulation rectifier without power source voltage sensors,and that the startup current is reduced about 50% by the soft-start process.