Power and Phase Monitoring

In most cases, it is advisable to have power and phase monitoring built into a control system. This allows a supervisory system (PLC, SCADA) to properly react for example to the failure of one phase in a 3-phase system. This approach protects motors from thermal overload, or reacting to brown-out voltage that could quickly and irreversibly damage  lamps in a UV disinfection system.

On a global scale, there is still insufficient uniformity of electrical standards, despite the fact that voltages and frequencies have now been agreed upon as listed in IEC 60038. In North America, it is permitted (and common) to connect equipment with higher power demand “single phase” between two phases of a 3-phase system (L1 and L2), which gives a voltage of 208 V / 60 Hz.

Three-phase configurations are more complex because the phase angle between the phases is 120° or 3 radians. There are two basic configurations: Δ (delta) and Y (wye or star). For details of configuration requirements, consult with your electrical engineer, or contact Osorno. It is important to understand that one of the characteristics of the Y configuration is that the combination of L1, L2, and L3 generates a neutral point that with perfect 3-phase symmetry does not carry a current.

Three-phase in Canada: Canada deviates from IEC 60038 by using  600 V/60 Hz for 3-phase systems.

Three-phase in USA: In USA, the “high-leg delta” (“wild leg”) system is often used, where one winding of a delta connected transformer feeding the load is centre-tapped and that centre tap is grounded and connected as a Neutral. This setup produces three different voltages. If the voltage between the centre tap (neutral) and each of the two adjacent phases is 120 V, the voltage across any two phases is 240 V, and the neutral to “high leg” voltage is 208 V.

On-line Power and Phase Control

As a component of the Wago 750 series, Osorno offers the Wago modules 750-494 (480 V, 5 A) and 750-495 (690 V, 5 A). The latter can be used with Rogowski coils for currents up to 500 A or 2,000 A. Both modules allow monitoring of

  • Active power;
  • Phase position;
  • Reactive power/energy;
  • Apparent power/energy;
  • Rotary field detection;
  • Power factor;
  • Frequency measurement;
  • Four-quadrant operation; and
  • Harmonic analysis up to the 41st harmonics.