line reactor and load reactor for variable frequency drives

AC line reactor, just show as what name it's, is connected on the ac input line side of a variable frequency drive, to counteract instantaneous voltage spike in the power grid line and protect the vfd from damaged by voltage surges, hence to enhance its service life, on another side, the line reactor can reduce harmonics produced by the ac drives to affect original power grid lines.

Load reactor, also known as output reactor, is connected between the ac motor and variable frequency drive, to protect both of the vfd drives and motors. In case of the ac motor in a short circuit condition, then the ac reactor is the right way to make the power line current in an allowed level. Another factor is the reactor can absorb current surges generated by the ac motor loads which will feed back to the power lines and might cause the variable frequency drives in an unstable state. Besides the motors, in Pulse Width Modulation voltage & frequency changing, the capacitance and inductance of the vfd drive can result in very high voltage peak to the ac motor power line side especially in long cable connection, therefore, it's necessary to apply an ac reactor between the drive and motor to avoid motor life shorten.