Polymer Films

ELECTROMAGNETIC POWDER CORES


	Thin films of Propyltrimethoxysilane (PTMS), have been shown to be an excellent insulator. The research shown on this page is focussed on using PTMS to coat iron powder which is in turn pressed into an electromagnetic core. The pictures above and on the left are of the coated iron particles, and the pressed core(wound with primary and secondary coils.

CORE	DENSITY OF POWDER ( kg.m -3 )	DENSITY OF CORE ( kg.m -3 )	RATIO OF DENSITIES	Percentage of theoretical density (7870 kg.m -3 )
UNCOATED @ 800 MPa	2414	7288	3.02	92.6
12% @ 700 MPa	2777	7116	2.58	90.4
12% @ 800 MPa	2812	7130	2.54	90.6
16% @ 800 MPa	2895	7209	2.49	91.6

The best theoretical density percentage range from 93% to 95% for compacted cores and clearly the obtained values in the table(left) compare well. These high-density values are expected to provide low hysteresis loss and in turn provide a respectable power output in comparison with other powdered cores.

Electrical Characteristics

The impedance of the cores was measured and is tablulated on the right. A typical hysteresis curve for one of the cores is shown below. The the total core losses calculated from the area of the hysteresis curve is given on the right. Note two values at different magnetic field strengths were measured for the uncoated core as a calibration. When plotted on a semilog graph, the magnetic field strength is approximately linear with the total loss of the core.

Core	Total Loss (W/kg)	Ln(loss)	Maximum B (T)	Impedance (m W )
Uncoated 1	7.06	1.95	0.85	19.7
Uncoated 2	17.57	2.87	1.32	19.7
12% 700 MPa	9.30	2.23	0.98	175.5
12% 800 MPa	11.56	2.45	1.16	76.5
16% 800 MPa	8.81	2.18	0.98	69.4

The core loss for the uncoated core is 9.5 Wkg. and the 16% PTMS core is approximately 8.5 W/kg. Therefore the 16% core reduces the total loss by 10.5% of the uncoated core. Typical core losses for a magnetic field strength are range from 1– 8 W/kg.