Magnetic Field (EMF) Analysis

Method & Standards

Magnetic flux density is calculated using the Biot–Savart law for infinite straight conductors. Vector superposition is used to combine contributions from all conductors in the cable tray cross-section:

B = (µ₀ / 2π) × (I / d)   [per conductor]

where µ₀ = 4π × 10⁻⁷ H/m, I is the RMS current (A), and d is the perpendicular distance from the conductor axis (m). The resultant peak field is found by scanning the 360° phase cycle.

Compliance limits (ICNIRP 2010):

  • Occupational (50/60 Hz): 1000 µT
  • General public (50/60 Hz): 200 µT

References: IEC 62110:2009, ICNIRP 2010 Guidelines, IEEE C95.6-2002, WHO EHC 238 (2007).

Cable Tray Configuration

RMS current per phase in each cable set.

Cable tray inside width in inches.

Measurement

Perpendicular distance from the outer edge of the tray to the measurement point. IEC 62110 recommends 0.3 m (≈12 in) for close-field assessment; 1 m (≈39 in) for general workplace compliance.