1. ENERGY TRANSMISSION SYSTEM FOR ARTIFICIAL HEART

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

3. 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

4. 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

5. 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:

7. 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

11. 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

12. 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

13. Input Voltage and Converter Type

16. Control of the System

17. 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

18. Reference www.ieee.org www.wikipedia.org www.medscimonit.com