Research of the inverse time characteristic curve for the electronic thermal relay

In order to make the protection characteristic of the electronic thermal relay conforming to the temperature-rising law of the motor, the disadvantages of action characteristic of the simulation electronic motor protector are analyzed in this article based on the international standard inverse time action math model for the electronic thermal relay, and inverse time characteristic of the simulation electronic thermal relay is also modified here by using the reverse exponential volt-ampere characteristic of the regulator tube´s PN junction. It has been proved that the method had the advantage of simple operation and good effect. Heat-resisting ability of the electromotor can be fully exerted here and the electromotor trips timely under the conditions of over loading. Three phase unbalance or phase failure can also be ensured. The protection performance meets the JB3905 demand.