ENERGY TRANSMISSION SYSTEM FOR ARTIFICIAL HEART

Contents Introduction Artificial Heart Energy Transference Scheme Determination of Control Region System Design Input Voltage and Converter Type Control of the System Conclusion Reference

Introduction Electrical circulatory assist devices use brushless dc motor as its pump Electrical energy is transferred to these devices transcutaneously using a transcutaneous transformer Transcutaneous transformer has large leakage inductance which reduce its efficiency Dc-dc converter employing secondary side resonance can be employed to alleviate this problem but the transfer gain of voltage varies widely with coupling coefficient Converter employing compensation of leakage inductance on both sides of the transformer offers stable gain and high efficiency

Artificial Heart Mechanical heart which completely substitutes the natural heart anatomically and physiologically Extra pumping chamber that can pump blood throughout the body Can be used either temporarily or permanently Made up of metal and plastic Has 5 major parts Energy Source Control and driving system Energy conversion system Pump actuator Blood handling parts

Energy Transference Scheme Use method of compensation of leakage inductance on both sides of the transcutaneous transformer In this scheme capacitors are added in series to compensate the leakage inductance Voltage gain of the converter is:

Determination of Control region Gv curve is divided into 3 regions: low frequency, middle frequency and high frequency regions Region II provides maximum transfer gain but is very sensitive to changes in load and coupling coefficient, hence not used Region I and III can control output voltage Region III is desirable because the unity gain frequencies is much less sensitive than for region I

System Design Output requirements: V0 = 24V Iomax =2.0A I0min =0.5A Size, geometry and core material of the transformer and range of air gap and misalignment between them are already defined For transformer windings the same cores used in series converter are used

System Design Transformer Core: Ferroxcube Pot Core 6656 3C8 Ferrite OD=2.6in Thickness=1.1in Air gap=10-20mm Misalignment=0-10mm Region III of gain characteristics is selected for control Low value of Q is selected to reduce sensitivity if variation Compensating resonant frequency is chosen at 120kHz

Input Voltage and Converter Type

Control of the System

Conclusion Converter employing leakage inductance compensation of transcutaneous transformer provides high voltage gain and reduced circulating current A control region of operating frequency is determined The converter offers high efficiency Minimized configuration of the devices in the thorax is experimented

Reference www.ieee.org www.wikipedia.org www.medscimonit.com www.ferroxcube.com www.sciencedaily.com www.synchardia.com www.essortment.com