TN系统低压变频回路电动机散热风扇的配电保护设计

Design of Distribution Protection for Motor Cooling Fans in Low-voltage Frequency Conversion Circuits of TN Systems

TN系统0.4 kV低压变频配电回路电动机散热风扇容量小、配套供电电缆截面小,特点突出,对其配电保护设计进行探讨,特别是长距离配电时回路的间接接触防护。采用断路器或熔断器作为保护元器件时,根据计算最小接地故障电流的近似公式,可反推出最大的防护配电距离,为电气设计人员提供设计参考依据。

The motor cooling fans in 0.4 kV low-voltage frequency conversion distributing circuits of TN systems have disadvantageous features such as low capacity and small sectional area the corresponding cable.This paper discusses the design of its distribution protection,with an emphasis on indirect contact shock prevention for distant distributing circuits.With respect to practical electric designs,the paper recommends the use of the approximate calculating formula of minimum ground fault current to deduce the maximum protective distribution distance for circuits with breakers or fuses as protective components.