THREE PHASE VS SINGLE PHASE SYSTEM ELECTRONIC EQUIPMENT- WHAT'S THE DIFFERENCE, WHICH IS BETTER? BASIC INFORMATION

When to use single phase, and three phase system?

Some power conditioning and electronic load equipment are operable only from a three phase power source. Often single-phase equipment can be operated directly from a single phase component of a three-phase system. However, these alternatives should be carefully determined before selecting an electrical system design.

The acceptable voltage limits of all equipment must be determined and carefully evaluated to ensure proper operation on the electrical system into which it is installed. Some equipment may have features such as internal taps or other adjustments that will allow it to accept common utilization voltages.

When evaluating the choice between three-phase and single-phase systems, consideration should always be given to the fact that three-phase systems may generally support larger loads with greater efficiency. In addition, the source impedance of three-phase systems is generally lower than single-phase systems, which is important to minimize voltage waveform distortion due to nonlinear load currents. Three-phase power may also be derived from single- phase systems.

However, the derivation of three-phase power from a single-phase system is not always practical and is not recommended. Certain methods of converting a single-phase circuit to supply three-phase loads such as capacitor phase shifters are considered inappropriate for electronic load equipment and may damage these loads per IEEE Std 141-1993.

Still other methods, such as utilizing single-phase motors to drive three-phase generators, may be used to convert single-phase to three-phase. Even so, special precautions should be observed such as balancing the load among the three phases.

Most three-phase electronic load equipment cannot tolerate the application of single-phase power to its input. The resulting downtime and equipment damage can be extensive.

Because fuses and circuit breakers generally cannot prevent all types of single-phasing conditions, recommended practice is that electronic phase-failure or voltage-unbalance relays be installed where necessary to mitigate single-phasing events.