I model in Lionel O Gauge, HO and N. I have a number of Old Lionel Transformers…like the ZW and # 1032. Now Lionel rate their transformers in Watts while in HO and N the Input and Output specs are written right on the box…ie for the MRC control master II the specs are:
Input: 120 V AC/ 60 HZ
Output: 20V DC, 17V AC, 22V DC
Total Output: 12VA
All of which is pretty straightforward to understand BUT for the Lionel transformers I can’t find the corresponding electrical specs.
SIMPLY, What “rule of thumb” can I use to calculate the approximate Input and Output Volts and Amps of a Lionel Transformer of any Wattage? Am I missing something here?
There are 3 outputs on the MRC transformer, the 20V DC is probably the variable DC fo rrunning trains, the 17V AC and 22V DC are fixed voltage for running acessories.
Also, the output on old Lionel transformers is usually AC, so it should not be used for the HO or N scale locomotives.
The best way would be to measure it. You could calculate it as well.
If you know the wattage and the output voltage, divide the wattage by the voltage. This should give you the current. Or something close to it.
The formula for VA (Volt-Amps) is volts multiplied by amps. Watts equals VA multiplied by the power factor. For an AC output, the power factor is probably going to be in the range of 0.9 to 0.95, or even closer to 1.00. Depends on how well the transformer is designed.
For DC, you just use the VA figure, as there is no power factor. That is an AC only thing, caused by things like capacitors and transformers. They alter the relationship between current and voltage, and introduce things like true and imaginary power. In that world, VA does not necessarily equal watts. But AC Volts times AC Amps times 0.9 is probably a pretty good guess of the wattage.
A note of caution. Lionel rated its post-war transformers based on input power, not output power. By using input power, they had a higher “watt” rating. But a transformer is less than 100% efficient, so you could never get the full rated power out of a Lionel transformer. Using my favorite Lionel transformer, the 1033, as an example, I have 90 watts input power. But if I try to draw more than 75 watts out, I’ll either pop the circuit breaker (hopefully) or overheat the transformer.
The mighty ZW is only good for about 225 watts out continuously. If you use all 4 “throttles” on the ZW, you have less average power per throttle available than the 1033.
My rule of thumb is to rate the output of Lionel postwar transformers at 75% of their input watts. Then divide that figure by 16 volts for amps available. This generally the current for which the factory circuit breaker is set. For example, the 1033: 90 watts times 0.75 = 67 watts. The circuit breaker is set for about 4 to 4.5 amps, which is 64 to 72 watts at 16 volts.
Modern Lionel transformers are correctly rated in VA or watts at the output, as that is what is required for a UL listing.