You are working on the design of a new facility. The electrical riser of the building with high current power is located close to the area where sensitive IT equipment in the computer room will be located. What should you recommend to reduce the amount of EMF coming from the electrical riser?

The most effective method to reduce the external magnetic field from a three-phase power system is to minimize the physical distance between the phase conductors. A combined, multi-core cable (such as one using XLPE insulation) bundles the conductors tightly together. In a balanced three-phase system, the currents are 120 degrees out of phase, and their vector sum at any instant is zero. This close proximity allows the magnetic fields generated by each conductor to cancel each other out very effectively, significantly reducing the net external electromagnetic field (EMF) that could interfere with sensitive IT equipment.

A. Installing single-phase power cabling would likely increase the magnetic field for the same power delivery compared to a properly installed three-phase system.
B. Using three individual core wires increases the spacing between conductors, which creates larger magnetic field loops and drastically reduces the field-cancelling effect.
C. Bus bar trunking can still produce significant magnetic fields unless specifically designed with phase interleaving, making it a less inherently effective solution than a combined cable.

1. Geng, H. (2014). Data Center Handbook. Wiley. In Chapter 11, "Power Distribution," Section 11.5.3, "Electromagnetic Interference (EMI)," it is explained that keeping current-carrying conductors in close proximity is a key technique for reducing magnetic field emissions. This principle directly supports the use of a combined, multi-core cable. (DOI: https://doi.org/10.1002/9781118937528)

2. IEEE Std 1100-2005. (2006). IEEE Recommended Practice for Powering and Grounding Electronic Equipment (IEEE Emerald Book). In Section 6.3.3.2, "Wiring practices," it states, "The best way to minimize the magnetic field is to route all of the phase conductors and the neutral conductor (if used) of a given circuit in the same conduit... Using multiconductor cables that contain all the circuit conductors is also an effective way to minimize magnetic fields." This directly validates that a combined cable is the recommended approach.

3. Swenson, C. (n.d.). EECS 3318: Fields and Waves I Course Notes. Michigan Technological University. In discussions on Ampere's Law and inductance, the fundamental principle is established that the external magnetic field from a set of conductors is minimized when the "go" and "return" currents are as close as possible, maximizing field cancellation. This principle applies directly to three-phase systems bundled in a single cable. (Reference to general physics principles taught in university electrical engineering curricula).