Line reactors can protect motors and reduce power line distortion from VFDs. Do you have problems with your existing variable-frequency drives (VFDs)? If so, 3-phase line reactors may be a very viable solution. A line reactor acts not only as a current-limiting device, but it also filters the waveform and attenuates electrical noise and transients associated with the system. You can install reactors in HVAC equipment, pumping equipment, machine tools, elevators, printing presses, UPS equipment, computer mainframes, robotics equipment, ski lifts, wind generators, electric cars, cranes, trams, and many other types of equipment, to extend the service life of the VFD and motor. Harmonic attenuation. As the name implies, you'd typically use line reactors on the line side of a VFD, as shown in Fig. 1 at right. Harmonic compensated line reactors are specially designed to handle the waveform's harmonic content. By inserting inductive reactance into the circuit, which is a high impedance to harmonic frequencies, line reactors reduce the amount of harmonics produced by a VFD system. For harmonic reduction purposes, you typically apply 5% impedance line reactors to the input of motor drives 20 hp and higher. This reduces input harmonics to 35% total harmonic current distortion (THID) or less and minimizes the effects of harmonics on motors and other devices powered off the same electrical system. Drive protection. In situations where you have drives located very close to the incoming facility power source, such as a substation, they may be susceptible to any incoming spikes and other transients. This is because there may not be enough impedance (in the form of transformers, power feeders, and the like) to help counteract these transient voltage spikes. This situation can damage the front

end (diode section) of the drives or cause nuisance overvoltage tripping on the system. Installing a 5% impedance line reactor at the input to each drive helps counteract line spikes, keeping them from tripping or damaging the drives. On the other hand, if you have drives located far from the facility power source (as often seen in hospitals), they may be affected by line harmonics caused by other harmonic-generating equipment (nonlinear loads). In most applications, harmonic problems are best solved at their source. Look for large nonlinear loads, such as VFDs, and apply a 5% impedance line...

VFD protection. The load reactor also acts as a current-limiting device to protect the drive under motor short circuit conditions. Here, the line reactor slows the rate of rise of the short-circuit current and limits the current to an acceptable level. By slowing the rate of rise of current, the reactor allows time for protection circuits in the drive to react to the short circuit and trip out safely, saving the IGBTs. The reactor also absorbs current surges created by the motor load that might otherwise cause nuisance tripping of the drive. Machine jams, multiple motor switching, and other application...

factor correction capacitors on the electrical power grid, it creates voltage spikes. The impedance of the reactor in the input circuit helps prevent these voltage spikes and virtually eliminates nuisance tripping of drives due to overvoltage. A line reactor can also filter out pulsed and notched distortion, which can minimize interference with other electronic equipment like computers, PLCs, telecommunications systems, instrumentation, and other VFDs. The use of line and load reactors increases the reliability, performance, and efficiency of VFD systems, extends the life of both drives and motors,...