In a message dated 1/14/05 10:50:16 AM Central Standard Time,
craxd1@ezwv.com writes:
Sam,
The link provided earlier is correct in winding DC relays. I'll try to
explain it in a little simpler terms (theory). A DC relay acts different
than an AC relay in the current drawn in the coil because of different
impedances. In other words, an AC coil has inductance and a DC coil has
resistance. The trick to winding the DC coil is having enough wire in
length to provide enough resistance that it wont burn out with a DC
current applied. Also, to have enough magnamotive force to pull in the
armature of the relay. To get this high amount of resistance, you end up
with anywhere of a few hundred feet to maybe a thousand feet of wire to
get enough resistance for the right DC current at the operating voltage.
This is where the ampere turns comes in but it is different between AC and
DC due to the difference between inductance and resistance.
Best,
Will
Will,
His original relay with it's 4500 ohm coil resistance dissipates about 2.7
watts at 110VDC.
His new relay will have to dissipate approximately the same amount of
power, (if we assume the same magnetic efficiency). That would give him a
winding
resistance of only about 54 ohms at 12VDC.
If we use the 60VDC figure, the numbers look much better with a coil
dissipation of only 0.8 watts, which would equate to a 180 ohm coil at 12VDC.
Then he would have to choose a wire guage that would provide that many ohms
of wire resistance , handle any heat build up associated with continuous
operation, and still fit on his original bobbin.
If it were me, I would be looking to try to replace the original bobbin
with one from a 12VDC relay instead of trying to reinvent the wheel.
Regards,
Dennis O.
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