NOVELTY - A source resonator (102S) has several inductors of different sizes, and a power and control circuit configured to selectively connect to one of several inductors. A measurement circuitry measures one parameter of power transfer between the source resonator and the device resonator (102D). The connections between the inductors and power and control circuit are changed according to the parameter measured by measurement circuitry.    USE - Wireless power transfer system used in application such as powering devices such as robot, vehicle, computer, personal digital assistant (PDA) movable freely in room using source mounted on ceiling, under the floor, or in walls of room, powering or recharging electric-engine vehicle such as bus, and hybrid car and medical device such as wearable or implantable device, to power or recharge autonomous electronics e.g. laptops, cell-phones, portable music players, global positioning system (GPS) navigation systems, displays, sensors, industrial and manufacturing equipment, light, fan, drill, saw, heater, television, counter-top appliance, military device, heated or illuminated clothing, communication and navigation equipment, equipment built in vehicle and clothing and protective-wear such as helmets, body armor and vests, and to transmit power to physically isolated devices such as hidden, buried, implanted or embedded sensors or tags and power transfer from roof-top solar panels to indoor distribution panels.    ADVANTAGE - The quality factor of the magnetic resonator is maximized by changing connections between the inductors and the power and control circuit of source resonator according to parameter of power transfer between the source resonator and the device resonator. The coupling factor between the source resonator and the device resonator is maximized. The efficient wireless energy transfer over mid-range distances, over wide range of directions and resonator orientations can be achieved.    DESCRIPTION OF DRAWING(S) - The drawings show the explanatory views of the wireless power transfer system comprising the source resonator and the device resonator.    Wireless power transfer system (1000)    Device resonator (102D)    Source resonator (102S)