| 摘要 |
The method for protecting the motor from the overheat caused by the motor current comprises: (a) determining the heat limit coefficient (L) and the heat resistance efficient (R); (b) calculating the equation CT1=R∫0T1I2dt when the detected current (i) is 115% of the rate current, CT2=R∫0T2(i-i100)2 when the i is between 100% and 115%, or CT3=R∫f(i115-i)2 dt when the i is less than 100% where i100 is 100% value of the rate current and i115 is 115%,. The CT1 is added to the present heat value rate but if the sumnred value of CT2 is 60% less than the L, the CT2 is not added any more. The CT3 is subtracted from the present heat value; (c) releasing the relay (Ra) of the power supply if the added/ sultracted value is greater than the L.
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