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The power quality of the electrical environment can be compromised because of the action of the drive. Voltage surges and harmonics can be created on the system by the drives. These issues can be corrected utilizing several technologies. The surge protective devices are applied to the drive system to reduce the damaged occurred because of voltage surges while considering the harmonics' effects on those devices. 480 V is often the incoming voltage, but other voltages might be used. Usually, the incoming power is reduced to a lower voltage (typically 120 Vac) to provides power to the control circuit, which contains sensitive electronics.
In order to protect the drive system, it is essential to protect the drive input. Protection provided at this location can avoid any surge damage because of events generated on the electrical system from upstream sources, interaction of several drives on the same system, external events like lightning and switching surges created by the utility. A voltage responsive circuitry device that is parallely connected and that without frequency responsive circuitry is an ideal device for this location. As this location is vulnerable to impulse transients as opposed to ring wave transients, frequency responsive circuitry must not be used for this location.
In the drive, the most critical and sensitive area is inverter input, which must be properly surveyed and taken care of. If there are no extra capacitors are installed within this drive to mitigate harmonic currents, a parallel connected, frequency responsive circuitry device can be installed.
It is possible that surges from external sources or the environment created by the drive can damage the sensitive electronics of the control circuit. It is essential to protect this location. As a step down transformer isolates this circuit which has sensitive electronics, this location must have a series connected SPD with frequency responsive circuitry.
It is essential to protect the immediate drive output if the length of connection between the motor and the drive is more than 50 ft or if the connection is routed along an external wall. The immediate output protection is must when the connection length between motor and drive is longer, the high frequency signal occurs as a reflected wave from the driver's output that reach the motor and then reflects back and forth between both systems. "voltage piling" is the action that is created as the reflected voltage is added to the nominal voltage as well as other reflected waves. The SPD has the ability to reduce the voltage peaks of the reflected waves.
Also, protection at a location where the connection between the motor and the driver extends outdoors, exposed to the environment or close to steel structure of building, is must to reduce the effects of direct lightning or induced voltage surges because of nearby lightning. The surges can damage the drive, even if the motor input is protected.
Voltage responsive circuitry device that is parallely connected is ideal for this location. Frequency responsive circuitry must not be used for this location because of the high harmonic content of the signal due to the normal drive operations. Frequency responsive circuitry devices installation at this location can cause SPD failure. Voltage responsive circuitry device use at this location can eliminate this possibility.
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