magneticcoupling

Magnetic coupling is the transfer of energy or mechanical torque between two systems through a magnetic field, without or with minimal physical contact. In electrical engineering, it commonly refers to mutual inductive coupling between magnetic circuits or coils, as in transformers or inductive power transfer. In mechanical engineering, magnetic couplings provide non-contact torque transmission across a barrier, preserving hermetic sealing or containment.

Principles: When current flows in one conductor, it creates a changing magnetic flux that links another circuit, producing an induced voltage proportional to the mutual inductance M. The coupling coefficient k is defined as M divided by the geometric mean of the self-inductances (k = M/√(L1 L2)). The efficiency depends on M relative to leakage inductance; greater coupling yields higher efficiency. Distance, alignment, and material properties affect M.

Types: Core-based transformers use a magnetic core to channel flux and maximize M. Air-core couplings rely on air as the medium, with typically lower M. Wireless power transfer systems use resonant inductive coupling to extend range. Mechanical magnetic couplings use permanent magnets or electromagnets to transmit torque across a sealed barrier, enabling pump drives or shaft isolation. Magnetic gears use spatial field shaping to transfer torque without contact.

Applications: Power transformers, inductive charging (wireless charging mats and battery systems), sealed-pump drives, isolation of sensitive electronics, and non-contact torque transmission in specialized machinery.

Considerations: Design must manage core losses, eddy currents, and hysteresis; use laminated or ferrite materials to minimize losses; minimize leakage inductance through careful alignment and geometry; address safety and EMI concerns; operating frequency and temperature affect performance and efficiency.