給電機通電，它的線圈，會吸收電能，然后激發磁場，用來激發磁場的這部分功率，就是無功功率。顯然電機不能沒有磁場，也就是說電源線上的電流，部分是用來輸送無功功率的。為了減輕線路的負擔，若給電機并上電容，由于電容的無功正好和電感互補，電機所需的無功就由電容來承擔，進而減小了電源線上的電流，這就是補償的意義。

 What is the significance of capacitive RPC?

When a motor is energized, its coils absorb electrical energy and then generate a magnetic field. The portion of power used to generate the magnetic field is reactive power. Obviously, a motor cannot operate without a magnetic field, which means part of the current on the power line is used to transmit reactive power. To reduce the load on the line, if a capacitor is connected in parallel with the motor, the reactive power of the capacitor complements that of the inductor exactly. The reactive power required by the motor is then supplied by the capacitor, thereby reducing the current on the power line. This is the significance of compensation.