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Most buildings today have at least one elevator connected to an emergency generator. But there's a catch. When the power goes out, some generators can create problems for the solid-state components in a modern elevator. And that can cause a chain reaction that causes problems for other equipment connected to the emergency power system.
Since buildings rarely operate on emergency power, these problems are frequently overlooked.
The problem is that older generators have difficulty responding to the rapid changes in current required by solid-state elevator drives. The result can be variations in system voltage and frequency. Both can damage components in the elevator control system. To prevent problems, the system should be tested at least once a year. Testing should include monitoring the quality of power supplied by the generator with loads connected. If interference is detected, the sources must be found and fixed.