Patent ID: 7623327
Filing Date: 2009-11-24
Classification: B60L,B62D,B62K,H02H,Y02T

Abstract:
1. A motor protective device comprising: a motor; a motor driver for controlling an electric current I supplied to the motor; a temperature estimation means for estimating a temperature of the motor based on the electric current I supplied to the motor; and an overheating protective means for limiting an upper limit of the motor supply current in response to the estimated temperature of the motor, wherein the temperature estimation means includes a heating value cumulative means which cumulates the difference between a heating value and a radiating value of the motor attributed to the electric current I supplied to the motor along with a lapse of time and, at the same time, the radiating value is a function of the difference between a heating-value cumulative value Td calculated by the heating value cumulative means and an ambient temperature Tm, wherein the heating value is calculated as a multiplied value of a square of the electric current I supplied to the motor and a preset heating coefficient Kup, the radiating value is calculated as a multiplied value of the difference between the heating-value cumulative value Td and the ambient temperature Tm and a preset radiating coefficient Kdn and, at the same time, the heating coefficient Kup and the radiating coefficient Kdn are set such that a cumulative simulation temperature TS is set by the formula: