How to Save Your Motors During a Brownout - Understand the effects of undervoltage and be aware of some methods for protecting your 3-phase motors against it

摘要

Undervoltage is defined as a condition where the applied voltage drops to 90% of rated voltage, or less, for at least 1 minute. Low-voltage conditions occur when a facility asks for more power than the line can deliver. But take note that it's not always an issue of the electric utility not having adequate capacity - transformers can act like a choke, restricting how much total power gets through to your system. Perhaps the facility (or a neighbor on the same electric utility transmission line) added new equipment and increased the load beyond what the line could deliver. In isolated cases, maybe the facility added a motor with a long cable run, and the voltage drop in that circuit resulted in low voltage at that motor. Brief low-voltage conditions can also happen when someone starts a large load without notifying the power company, or when the power is shorted to ground or to another line. Even loose cable connections can cause low voltage.