How to design the power frequency magnetic field immunity of the motion controller MC

The design of the motion controller (MC) must address its low-frequency, high-penetration characteristics in response to power frequency magnetic fields. Magnetic field-sensitive components such as Hall effect sensors, current transformers, or unshielded inductors should be kept as far away as possible from magnetic field sources such as transformers and motors. If this is not possible, use high-permeability materials such as permalloy for shielding. Twisted-pair cables should be used in the signal loop to cancel induced differential-mode voltage. In circuit design, for analog signals that may induce power frequency interference, use instrumentation amplifiers with high common-mode rejection ratios, followed by digital notch filtering. Digital circuits are less directly affected by power frequency magnetic fields, but power lines may induce interference; therefore, common-mode inductors should be used at the power input.

Testing should be conducted according to IEC 61000-4-8, placing the module in a power frequency magnetic field coil and monitoring its functionality, particularly analog measurement accuracy and communication error rate. For extremely high magnetic field environments, it may be necessary to reselect sensors or use a magnetically shielded enclosure.