Wiring Ammeters

I can't find the formula you show, but I don't think it matters.  Amperage (current) depends on the load.  The power sources provide as much current as the load requires up to their maximum capacity.  Ammeters do not measure the maximum current a power source is capable of putting out (unless the load happens to require that amount of current).

When it comes to amps, the load on the circuit (the trains) will only draw the number of amps it needs to run. You could hook up a 1,000 amp power supply to your trains and the ammeter would still show only a 6 amp draw.

Thank you, Yes, I understand that the load depends on the demand. The root of the question is ... when I had 2x135w (15a @18vac) i was having a condition where the lockons would reset as if there was a short when I powered up the layout. I never found a short per-se but removing lighted rolling stock or a locomotive would mitigate.   The diagnosis was add more power, so I did,the problem has abated but the total draw seems well below 15a.   it may be that one of the powerhouse was being taxed more heavily than the other due to location on the layout causing an overload. I can reproduce the original overload problem by simply powering off all but one of the 135s, so I know the load, at least at initial power up is greater than the 7.5a that a single 135w can provide.  So I'm satisfied that I wired the meters correctly and I understand the original problem.  Thanks again.

Can someone comment on average amps verses rms amps?  I was hoping to put together an amp monitor and overcurrent trigger but base it on rms amps.  Is that the wrong thing to do?

Anthony

I think RMS measurements are the most accurate, but they're also fairly hard to do with non-linear waveforms without some heavy lifting.

Truthfully, average current of a pure sine wave is zero, think about it.

Over one cycle.  To get RMS current over that same once-cycle period you'd have to average over 1/2 cycle instead (i.e. get the first half of the one-cycle period) and multiply by two (to approximate, and include, the second half).

Mike

Point well taken, GRJ. 

RMS is not average.  It's Root Mean Square.  Some googling will surface explanations.  FYI, also of relevance is peak.  For example, a 120 volt AC circuit is around 170-180 peak voltage, so components should be rated accordingly.

For a discussion, go to: https://www.electronics-tutori...its/rms-voltage.html

Well it's easy. It's the square root of arithmetic mean of the squares of the values of the waveform. Thus the root-mean-square. Note that squaring the values of the waveform does away with the negative signs of the negative half cycle.

@LIRR-Jim posted:

Recently I made a post regarding a power problem I was experiencing.  The suggestion was that I add more power which I did.  I augmented the 2 135w Powerhouses with two 2 180w.  After adding the first 180w powerhouse the problem indeed went away.   I decided I would like to monitor power consumption so I added a 0-10A Ammeter to each supply expecting that a 135w would show about 7.5 amps and a 180w about 10 amps at full capacity.   What I am seeing is about 6 amps total across all 4 sources, about half the capacity of the original 2x135 arrangement.   What am I missing, if anything?  I'm using I_(A) = P_(W) / (PF × V_(V)) via the calculator at https://www.rapidtables.com/ca..._Amp_Calculator.html.  The meters are https://www.amazon.com/gp/prod...00?ie=UTF8&psc=1 wired in series on the A side (red) between the lockon and the load.    As always Thanks.

Clearly, two PH135 transformers in parallel should be able to provide more than 6A and maintain their rated output voltage, so I'd say something else was afoot there.

I think we'd need to know more about the exact configuration and circumstances of the power drop to analyze what is really happening.  This doesn't sound like the typical "insufficient" current supply situation.

Exactly what I thought ... And I can get the overload on powerup with one.  I've attached a diagram with the 2x 135 arrangement.  Generally, when the suspected overload occurred, it was power A ... the yard above that would typically have 4 Legacy class locomotives and 12-14 lighted coaches.