if one load is lost in a factory lighting system with a 3 phase 4 wire alternating current supply what happens

Question

will all lights go out?

Answer 1

Most factories take a 4-wire service. In the US this is typically 120/208 or 277/480 V. For the remainder of this answer I will assume the customer is served with 277/480 V.

The lighting equipment is designed for phase-to-neutral connection. i.e. 277 volts. The various lighting circuits are split between the three phases. One third wired A-phase to neutral, another third B-phase to neutral, and the remainder C-phase to neutral.

If one lighting circuit were to be lost, the remaining 2/3 of the lights will continue to operate. With less lighting load compared to the other two phases, the voltage would be slightly higher. This would cause a small voltage imbalance across the three phases. Probably not enough to cause problems with the rest of the equipment in the factory.

Answer 2

When one load in a factory lighting system is lost one line may be cut off by a busted fuse or an overheated circuit breaker terminal. Voltage in the lighting circuit should be checked for possible higher voltage than it was designed to operate. Operating the lights in this condition may result to early failure of the lamps.

Answer 3

Depends how it's been wired. Usually in a 3 phase supplied multi-storey building its one phase per floor so one floor would be in the dark..

Answer 4

By "one load lost" I assume you mean, for example, the overload trips on a machine, bringing it suddenly offline. This will not affect the other circuits in the facility, which are connected in parallel.