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Reply to "Help Guide - What to do if Lion Chief Locomotive Stalls when Activating Operating Track, Uncoupler, or Crossing Gate - Expanding an O Gauge Set"

@Long Hair posted:

I think part of the confusion here lies in different users have different experiences of what the phrase "run the uncoupler" means.  On the starter set DC transformer, I have seen mine uncouple cars daintily as they slowly roll across.  On AC and more power (but less voltage), I've also seen them buzz loudly like electric doorbells and uncouple much more assertively.  No word in the manual either about how much performance or buzzing to expect.

To hopefully clear up some confusion, in addition to knowing the current ratings of the other LC Transformers being mentioned in this Topic (in John's case its 18VDC x 2300MA = 41.4Watts; thank you @Craftech John), here is some additional information that may be helpful.

Long Hair, the dainty vs. buzzing operation of the uncoupler you refer to has to do with the magnetic fields generated by Direct Current versus Alternating Current.

When powered by DC voltage the field polarity (North South) of a electromagnetic coil is constant, it always points in the same direction (given the same positive and negative electrical connection).

When powered by AC voltage, the field polarity of an electromagnetic coil reverses 60 times per second (in the US at the Utility power frequency of 60Hz). Even though it exerts an overall pulling force, this oscillating magnetic field also vibrates any ferrous metal in close proximity to the coil (like the uncoupling thumb tack or plate under our train cars' couplers) creating the buzzing sound you hear.

Maybe you already know this, but there are two different things having to do with power here, and as we know, Power(in Watts) = Volts x Current (In Amps, also referred to as "I").  

Transformer power Output is the Volts times Amps it's capable of delivering to an electrical load before the transformer either overloads and overheats melting the internal wire insulation or (in the case of modern UL Approved transformers) cuts off due to internal protection when its capacity is exceeded.

From Ohm's Law and Watt's Law, we know that the power the uncoupler (coil) draws (actually uses from the transformer) is dependent upon the applied voltage and the coil impedance (resistance and inductance).  This impedance varies with frequency. DC=0Hz.  AC=60Hz.  This means that a coil will draw different amounts of current at different voltages and frequencies and with an AC or DC source.


Below is a quote from the following website that gives a simplified explanation of current draw by an AC coil (like the Uncoupler) when operating on DC voltage.  The discussion is about solenoids, but the AC/DC principle is the same because they are both AC Coils.

https://tameson.com/choosing-a...-solenoid-valve.html

"Using a coil rated for AC current with a DC supply is possible, but the voltage (and the current) must be limited or else the solenoid (coil) might burn out. The reason for this is that in AC regime, coils have an inductive reactance that adds up with the electrical resistivity of the coil. As a result, the impedance of a coil is several times higher in AC regime than in DC regime. As an example, using a 24 VAC rated solenoid valve with a 24 V DC power supply would most likely damage the solenoid because the effective current flowing through the solenoid would be much higher with DC voltage."

OGR Publishing, Inc., 1310 Eastside Centre Ct, Suite 6, Mountain Home, AR 72653
800-980-OGRR (6477)
www.ogaugerr.com

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