Need to calculate relay coil voltages.
Need to calculate relay coil voltages.
(OP)
I am trying to find a method of calculating the operating voltage of a series of relay coils. These relays/coils are drop in replacements for Otis Elevator controllers. The relays are used for energizing elevator door motors, the elevator motor, releasing the elevator brake, just about everything the elevator does that is controlled by relays. They are old technology, pre 1980’s (though the relays are new). Otis typically used 135VDC and there might be 1 to 3 relays in series. However, there may be some AC coils mixed in and possibly some 240V relays.
One example relay is the replacement for the Otis O21A20Y1 that uses an Otis 222CY1 coil. The coil uses 15,310 turns of #39 gauge magnet wire with polyurethane or SFV insulation. The resistance is 3,384 ohms +- 10%. The wire is wound on a bobbin with a 0.773 inch outer diameter core. This sits on a 5/8 inch E magnet iron core. The core length is 1.498 inches and weighs about 0.148 lbs. The main mass that it is pulling is the 1.975x1.250x0.156 armature clapper. The clapper is made of E magnet iron. It is pulling against a 5 oz spring. The relay pulls the clapper a distance of 0.171 inches. It is non-latching.
My best guess is that this is a 135VDC coil but I would like to know for sure.
One example relay is the replacement for the Otis O21A20Y1 that uses an Otis 222CY1 coil. The coil uses 15,310 turns of #39 gauge magnet wire with polyurethane or SFV insulation. The resistance is 3,384 ohms +- 10%. The wire is wound on a bobbin with a 0.773 inch outer diameter core. This sits on a 5/8 inch E magnet iron core. The core length is 1.498 inches and weighs about 0.148 lbs. The main mass that it is pulling is the 1.975x1.250x0.156 armature clapper. The clapper is made of E magnet iron. It is pulling against a 5 oz spring. The relay pulls the clapper a distance of 0.171 inches. It is non-latching.
My best guess is that this is a 135VDC coil but I would like to know for sure.
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RE: Need to calculate relay coil voltages.
Suggestion: The following could be considered:
References:
1. Giacoletto L. J. "Electronics Designers' Handbook," 2nd Edition,
McGraw-Hill Book Co., 1977
2. Warrington A. R. van "Protective Relays Their Theory and Practice,"
Volume I, Chapman & Hall, Ltd., 1971
Relay voltage range estimation:
1. Constraint: AWG B&S Wire Gage 39 has an operating current of
Idc=0.01264 Amp listed in Table 3.14, Reference 1. This implies DC
voltage (assuming that the relay has a solid iron core suitable for DC
magnetization/operation):
Edc=Rdc x Idc=3,384 x 0.01264=42.77VDC
2. Constraint: The DC coil imput parameters Idc and Edc must develop
relay operating force greater than 5oz relay spring force.
Elementary formula for the force F, magnetic induction (flux desity),
length of wire L, and current I in the coil:
F=B x I x L which has to be properly applied to the relay coil magnetic
geometry.
Reference 2 indicates "pull force F" Equation (2.10) on page 2.4 as
F=(2 * (pi) * (N * Idc)**2 * A)/(x**2)
where
F=force
Pi=3.14
N=coil turns
Idc=coil current
A=pole face gap area
x=air gap at the pole center
**2=exponent 2
Take off appropriate relay parameters and substitute them into the
above formula to verify that the Idc is adequate to develop F > 5 oz