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alex157(at)pwhome.com
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 Posted: Tue Mar 13, 2007 5:03 pm Post subject: Comments please on this solid state contactor....... |
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I have been testing my electrical system on my all- electric Velocity- with
no load, only the coils energized for about 30 minutes my battery contactors
were both quite hot- too hot to hold for more than say 5 seconds- comments
from other builders agree that this is rather normal- someone suggested the
"Czonka III" solid state unit- uses no appreciable power- good for tens of
thousands of cycles at 200 amps- please see attached PDF- is there any
foreseen drawback other than cost?
Alex
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jrichard(at)ccser.com
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| Posted: Sat Mar 17, 2007 7:07 am Post subject: Comments please on this solid state contactor....... |
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Hello Alex
I have installed the EV200 contactor in my Lancair Legacy as the master
contactor after some investigation. I posted a similar question on the list
about a year ago and Bob answered me back (thanks again Bob). He said it
looked good from the data sheet, but very expensive when compared to the
normal contactors from B&C.
I think the current switching and carrying capability is a little over-kill
for our applications in light airplanes. However, in an all electric
system, I think this is not all bad. There's no weight or size penalty.
It's reassuring to note the device has a mechanical life cycle spec and a
cycles under load spec. As a master contactor, most of the load is removed
during the switching event. Load carrying is speced at 200 A continuous and
500 A for 10 sec. However, as a starter contactor, load switching is an
issue but that's where this thing really shines. Because of cost, I ended
up using a regular contactor for the starter.
The coil energizing circuit is unique. It draws about 3 A during coil pull
in then drops back to 0.07 A (24V) to hold. I talked to the design engineer
to learn this low holding current is achieved by a pulsing circuit that
applies the 3 amps at a very low duty cycle. A possible down side of the
pulsing is radio frequency interference. I did a rough test with my
handheld placing the antenna all around the device and the coil leads and
found no interference across the nav and com bands. I'm not flying yet, so
I'm still waiting to conduct the real test. In comparison, a continuous
duty standard contactor I have has coil resistance of about 70 ohms for 24
volt operation. At 28 volts that will draw about 0.4 A and dissipate about
11 watts. Not that much in the big picture. Obviously, the EV200 does not
get hot at all due to coil current. Finally, it's reassuring to note the
coil circuit operates over the range of 9 to 36 volts and will hold in (stay
closed) down to 7.5 volts. In a 24 volt system, this is more than adequate
margin to operate under low bus voltage, even when starting. I think it's
about the same as a 12 v contactor too.
It is definitely a quality component and I'm banking on it keeping my two
Odyssey PC 625 batteries connected to the panel.
Regards,
John Richardson
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