Magnetic field measurements near RF induction heaters

Area of Science:

• Occupational Health and Safety
• Electromagnetics
• Industrial Hygiene

Background:

• Radiofrequency (RF) induction heaters are common in industrial settings.
• Understanding magnetic field exposure is crucial for worker safety.
• Previous measurements of RF induction heater magnetic fields are limited.

Purpose of the Study:

• To measure magnetic field strengths around RF induction heaters.
• To assess potential worker exposure to these fields.
• To characterize the performance of a new magnetic field measurement monitor.

Main Methods:

• Measurements were conducted using a portable survey monitor developed by the National Bureau of Standards (NBS) for the National Institute for Occupational Safety and Health (NIOSH).
• The monitor features a wide dynamic range (0.01 to 10,000 A²/m²), frequency range (300 kHz to 100 MHz), and isotropic response.
• Magnetic field strengths were measured near 16 RF induction heaters at various distances from the loop applicators.

Main Results:

• Maximum measured field strengths (uncompensated) ranged from 15 to 4,500 A²/m² at close proximity (5-51 cm) to the induction heaters.
• At typical worker locations (30-76 cm), field strengths ranged from 0.01 to 300 A²/m² (uncompensated).
• The monitor demonstrated high probe burnout protection (20,000 A²/m²) and accuracy (+/- 1.0 dB).

Conclusions:

• The study provides initial data on magnetic field strengths around RF induction heaters.
• Measured field levels at worker distances suggest the need for further exposure assessment.
• The NBS/NIOSH monitor is a capable tool for characterizing magnetic fields in industrial environments.