Significance, Development, Replication

Background
Robert Adams of New Zealand is credited with the invention and development of the motor that bears his name around 1969. The complete formal description is: High Voltage Pulsed DC Permanent Magnet Switched Reluctance Electric Motor. The term Switched or Variable Reluctance first appeared, curiously, also in 1969 in a paper by Nasar in IEE Proceedings. Credit for the first reluctance motor goes to Davidson's electric locomotive in 1838. Stepper motors used in ink-jet printers, floppy drives, and robotics are common examples of switched reluctance motors that achieve high performance, continuous torque operation by using closed-loop magnetics but without permanent magnets.

Principle of Operation
In the case of the Adams motor, permanent magnets are used in the rotor to avoid the need for commutators rendering it in effect a brushless DC motor. Its operation is explained in various and sometimes conflicting ways. Most describe both a positive torque induced by the magnetic attraction produced between the approaching rotor magnet and the passive ferromagnetic stator core followed immediately by a negative torque produced by the repulsive magnetic field that appears as the stator coil is energized just as the rotor magnet and stator core reach opposition.

Adams increases performance further by taking advantage of the collapsing magnetic field and capturing the induced back-EMF current in the stator coil. This is performed by the second battery in the diagram above (BAT2) which is charged by the back-EMF as it is routed through rectifier D1, but which also prevents discharge of BAT2 back through the coil windings. This two battery design would require periodic swapping of the batteries.

Motor Mystique
The story behind the Adams motor is full of intrigue, conspiracy, and amazing claims, like so many other "free energy" devices, that feature superlatives ("the first working free energy device placed in the public domain") and alien-sounding expressions like "time reversed negative current" and "over-unity performance."

Many builders report "cold current" effects when the motor is properly "tuned." The switching transistor and drive coil wires are said to become cool or even cold to the touch.

Development
With such distractions aside--for the moment--there is enough credible documentation and evidence in existence to raise enough interest for a considerable number of exerpimenters to actually attempt and reportedly succeed in replicating this simple yet curious device.