Experimental comparison of macro and micro scale electromagnetic vibration powered generators

Electromagnetic vibration powered generators convert kinetic energy present in the application environment into electric energy. Such generators may be used as an alternative power supply to batteries in wireless sensor systems enabling indefinite and maintenance free operation. This paper presents an experimental comparison between macro and micro scale electromagnetic generators based upon an identical magnetic circuit and explores the influence of size on the performance and behaviour of these devices. The large scale traditionally fabricated generator exhibits the highest power density of 2615nW/mm³ compared to the microgenerator power density of 47nW/mm³. The macro scale device achieves the optimum damping conditions where electromagnetic damping equals parasitic damping. The level of electromagnetic damping in the micro scale generator is an order of magnitude less than the parasitic damping due to reduced electromagnetic coupling. This comparison highlights the challenges involved in scaling electromagnetic devices down in size.