The purpose of the test is to evaluate the immunity of electrical and electronic equipment when subjected to external magnetic fields at mains frequency generated by power distribution lines and electromagnetic induction-based machines (such as transformers, rotating machinery, etc.).
The current generating the disturbance under consideration may be that produced under normal operating conditions, resulting in a static magnetic field, or that produced for a few milliseconds under fault conditions, resulting in a short-duration magnetic field.
The test setup varies depending on whether the product is tabletop or floor-standing.
For tabletop equipment, the device is placed on an insulating support table inside the induction coil. The generator is positioned within 3 meters from the induction coil, with the connection cables intertwined.
For floor-standing equipment, it is positioned on a 10cm high insulating support resting on a reference plane made of a non-magnetic metal sheet, inside the induction coil.
The magnetic field is generated by supplying the induction coil with power from the generator. By adjusting the current flowing through the coil, the test magnetic field is regulated, which is measured by a current probe.
La prova viene eseguita con corrente:The test is conducted with current:
- At 50Hz or 60Hz according to the power supply frequency.
- In direct current.
- At a frequency of 16 2/3Hz in an electric traction environment.
The test can also be performed with an impulse magnetic field (1.2/50µs waveform), generated by a pulse generator closed on the induction loop.
The standards governing the test are:
EN 61000-4-8:
Electromagnetic Compatibility (EMC) - Part 4: Testing and Measurement Techniques. Section 8: Immunity Test for Power Frequency Magnetic Fields. Basic EMC publication.
EN 61000-4-9:
Electromagnetic Compatibility (EMC) - Part 4: Testing and Measurement Techniques. Section 8: Immunity Test for Impulse Magnetic Fields. Basic EMC publication.
Elettra has two magnetic field immunity test setups; they can achieve levels of 500A/m for continuous field and 1000°/m for impulse field.