1033 heat?

[Nish]

I have a 1033 transformer that I've been using since I started playing with trains last year. I haven't really had any problems with it until now. I've been continually adding to my layout , and when I added a 2400 series passenger set to my collection just recently, i realized that I'm approaching the load limit on my "juice box" with all the lights on the layout. I've backed off running the passenger cars and pulled the bulbs on my switch controllers to ease off the wattage until I get a second transformer The issue is that, even though I've budgeted my wattage, I still can't seem to run for more than an hour before I notice the engine start to get sluggish. The transformer hums quietly, but noticeably (never used to before, even after a couple hours running). The most worrisome thing is the heat coming off the transformer. I pulled off the whistle handle, and the handle stud is quite hot (but the speed handle stud is not). I pulled off the cover to look inside and probed everything to see if the heat was localized anywhere else, but other than the core being kinda warm, the heat is concentrated on the whistle handle assembly. The rectifier disk wasn't warm either (BTW, I never use the whistle controller other than direction) No loose solder points, no evidence of burning insulation, no delamination of the windings, basically nothing visibly deficient. I was able to move the winding within the core, even though it's still solid.  No idea what the deal is with that. Even though the heat is pretty considerable, the breaker doesn't trip.

I'll double check to make sure my constant voltage accessories are wired up correctly, but I wanted to see if anyone had some insight. I'm continuing to budget my wattage, and I'm shopping for either a second 1033 or splurge on a ZW so I can keep building the pike. (Army's not moving me for another year, so I have time to double my trackage before I tear it all down!)

Thanks!

John N. 

[lionelsoni]

All transformers draw a certain amount of current, called the "magnetizing" current, even when there is no load at all on them.  This current creates the magnetic flux in the iron of the magnetic circuit, which produces a voltage that counters the applied voltage to keep the magnetizing current from being excessive.  However, that iron can stand only so much before it becomes "saturated" and no longer prevents a heavy current from flowing.  That current flowing in the imperfect primary-winding conductor heats up the transformer.  The degree of saturation increases with increasing line voltage and with decreasing frequency.

Small transformers (like the 1033) are usually designed to allow a substantial amount of saturation, since they can more easily get rid of the heat than a larger transformer.  Compare the 100-watt V transformer and the 250-watt Z transformer.  The V has enough spare heat dissipation that it is rated at both 50 and 60 hertz, while the Z is limited to 60 hertz.  The 1033 is a pretty small transformer and is therefore probably operating farther into saturation than most.  It, like most postwar transformers, was designed for a line voltage of 115 volts.  But modern power lines often go above their nominal 120 volts.  My guess is that that's why your 1033 is overheating.

The circuit breaker will not handle this situation, since the magnetizing current flows only in the primary winding, and the circuit breaker is in the secondary winding.  Since you detect more heat on the whistle control switch, you might try to tighten the sliding connections there; but I don't think that will be easy.  I think you are wise to think about getting a bigger transformer.  Since you don't use the whistle control, you might consider the Z instead of the ZW.

By the way, if you're trying to reduce lamp current, don't fall for the idea that the 1445 is better than the 53 in this regard.  Just because it has a dual rating at 18 as well as 14 volts doesn't mean that it draws less current--it draws more at any voltage.