Since what come on TV at 9:00 tonight, I have better time to spend than listen
to that BS, so I figured I'd do the post I promised about the voltage
interchangability of AC and DC relay coils.
From; Struthers & Dunn Relay Engineering, 1950
For midget type 1 relay assemblies (Like antenna relays, P&B KUP Series, 10 amp
contacts, 1, 2, pole);
AC Volts = 115
Armature open current = 0.09 amps
Armature closed current = 0.057 amps
60 Hz impedance = 2037 ohms, P&B is 2250 ohms for 120 VAC, P&B 3PDT for 120 VAC
is 1700 ohms
Coil mark = 50A
Number of turns = 5000, 38 ga.
DC Volts = 35
DC current = 0.058 amps
DC resistance = 605 ohms
Core dia. = 3/8"
For For industrial type 1 relay assemblies (Large open frame clapper type,
25-30 amp contacts, like Magnacraft 300 and 389 series, 1, 2, pole);
AC Volts = 115
Armature open current = 0.14 amps
Armature closed current = 0.08 amps
60 Hz impedance = 1437 ohms
Coil mark = D
Number of turns = 4200, 32 ga.
DC Volts = 24
DC current = 0.13 amps
DC resistance = 180 ohms
Core dia. = 1/2"
Acceptable variance in resistance (tolerance) is 7-1/2%
For me, I would start at say 15 to 20 VDC and go up until the relay closes
normally. The hold in voltage is not near as great as the pull in voltage. I
remember someone saying they was operating 115 VAC relays on a higher DC
voltage around 24 or more volts DC I think on here. Between the two styles
above, we have a range between 24 to 35 VDC for normal operating voltage.
Anyhow, once it looks to be pulling in at the right speed, check the coil to
see if it's getting hot. Without the core having the shading coil, I would want
the DC supply to have a good filter cap so a steady DC current would be fed to
it. Without a capacitor, it will probably buzz. Also, make sure to put a diode
across the relay coil to kill the spike.
Best,
Will
Amateur Transformer
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