PW-ZW Transformer ampere capacity

The secondary winding on a PW ZW is common to all the handles. That means that the total power of the transformer is available at any one handle, or can be divided among the four handles. There are no "channels" on a ZW.

Using more than one handle has the advantage of not trying to get all the power through one roller. The rollers are the weak link, being made of carbon, and can get hot and fail after long steady use at high power. Another advantage of splitting the output is that you can use four (or more) buses, each controlled/protected by a cut-off switch/circuit breaker, with each handle set at whatever voltage you need for different types of accessories. 

The ZW is rated at 275 Watts (input.) Assume that it is 70% efficient. That means you may be able to get around 200 Watts out of it. I believe that this topic comes up occasionally on this Forum. You might want to search the archives to get the opinions of others who have considered this scheme, and who have a better grasp on the exact maximum capabilities of the ZW.

If the handle is set at 12.5 Volts, using Ohm's Law, (It's as easy as "PIE"...Power = Intensity x Electromotive force...or Watts = Amps x Volts) that's 16 Amps total. I would use a more modest estimate, say, 14 to 15 Amps.

Lionel stated that the 250 watt version of the ZW would supply continuously 180 watts at 14 amps. That is 72 percent.  Very close to Mr. Bloom's numbers.

I love it when J. Lionel and I agree on something.

I use my post war ZW for lighting and accessories and run four outputs thru four PSX-AC breakers. I generally run around 5 amps total pretty much split evenly between the outputs. Runs nice and cool. 

Page 23 of the attached 1965 Lionel Operating Manual has a table which gives the continuous output ratings for each of several Lionel postwar transformers.  The ZW is rated at 12 amps.  Given the date of the publication I would assume that is for the 275 watt version.

Bill

Be very careful paralleling handles on the post-war ZW, VW or KW transformers.  If you have them off by a very little, the result is basically a couple of shorted secondary turns on the transformer.  This makes it run very hot and also eats the carbon rollers much faster than normal.  It can also actually cook the enamel off the windings and ruin the core.

Consider the following example.  Note that I have made a "connection" between the B and C posts to parallel those outputs.  If you look at the effective circuit, the two rollers are obviously directly connected together.  Now just move one a very small distance on the core from the other one, the result is a direct short across the core windings.  This is a very bad idea!

Greenbergs Repair and Operating Manual for Lionel Trains has ZW 250 watts in 1948 and said can supply continuously 180 watts at 14 amps. Page 591

Page 586 lists the model "Z" last made in 1947 also at 250 watts and can supply continuously 180 watts at 14 amps. Page 586 so not sure if that is a typo or not.

Page 597 lists the ZW (R) but no ratings.

(quote) Be very careful paralleling handles on the post-war ZW, VW or KW transformers.(end quote)

No one has suggested that the OP wire his outputs in parallel.  I suggested to use up to the four handles for four separate buses. If you parallel the outputs, as GRJohn has pointed out, bad things will happen.

I wounder what the 275 watt will put out continous

Depends on (for one thing) the ambient temperature.

gunrunnerjohn posted:

Be very careful paralleling handles on the post-war ZW, VW or KW transformers.  If you have them off by a very little, the result is basically a couple of shorted secondary turns on the transformer.  This makes it run very hot and also eats the carbon rollers much faster than normal.  It can also actually cook the enamel off the windings and ruin the core.

Consider the following example.  Note that I have made a "connection" between the B and C posts to parallel those outputs.  If you look at the effective circuit, the two rollers are obviously directly connected together.  Now just move one a very small distance on the core from the other one, the result is a direct short across the core windings.  This is a very bad idea!

 

John, What would be the reason for connecting two posts, like the B & C ?   

Why would you parallel handles on a PW ZW if the total power capacity is available to any handle in the first place? I think you are confusing the ZW-C with multiple power supplies.

14 amps sounds like the right answer and all available to one handle. Sure, you could split that across handles with separate power districts. 

One thing I couldn't figure out is whether the 275 watt PW ZW could handle more than 14 amps if you set the voltage at much less than 18 volts, say 5v to 8v.

George

John isn't necessarily talking about directly connecting B & C together - he is talking about setting post B to say 14 volts and post C to 14 volts as independent buses that inadvertently get joined together. A common example is track blocks. Post B can control track block 1 and post C track block 2. When the train crosses these blocks, there is a time when the locomotive, tender, passenger, or other operating car has one pickup roller in block 1 and the other in block 2. This effectively connects post B and C together. The minute differences in voltage potential between the two posts essentially causes a short across some of the windings. In normal operation, this isn't instantly fatal, but parking a train in neutral for extended periods really heats things up.

Does having an inline breaker on A, B, C, and D alleviate the inadvertent parallel going block to block as described above?

JD

bmoran4 posted:

John isn't necessarily talking about directly connecting B & C together - he is talking about setting post B to say 14 volts and post C to 14 volts as independent buses that inadvertently get joined together. A common example is track blocks. Post B can control track block 1 and post C track block 2. When the train crosses these blocks, there is a time when the locomotive, tender, passenger, or other operating car has one pickup roller in block 1 and the other in block 2. This effectively connects post B and C together. The minute differences in voltage potential between the two posts essentially causes a short across some of the windings. In normal operation, this isn't instantly fatal, but parking a train in neutral for extended periods really heats things up.

Not to mention blistering the skinny wire connecting the two rollers, front and rear, together inside the engine or car.

My question,  does one have the same inadvertent connection mis-matched voltage problem with a train crossing "Blocks" if the the (2) two block power sources are from the "A" throttle on two (2) different PW - ZW transformers ?    I am powering the layout with (4) ZW's but only using the A throttle power from each transformer to create power to 4 individual blocks.    

chris a posted:

My question,  does one have the same inadvertent connection mis-matched voltage problem with a train crossing "Blocks" if the the (2) two block power sources are from the "A" throttle on two (2) different PW - ZW transformers ? ...

Yes, with regard to the damage potential to the equipment, but not to the secondary windings on the ZW.

OK thanks for the explanation.  

ADCX Rob posted:

chris a posted:

My question,  does one have the same inadvertent connection mis-matched voltage problem with a train crossing "Blocks" if the the (2) two block power sources are from the "A" throttle on two (2) different PW - ZW transformers ? ...

Yes, with regard to the damage potential to the equipment, but not to the secondary windings on the ZW.

Sorry if the answer to this is obvious, but will a quick acting breaker on each of the variable lines trip when voltage is mismatched, bridged, and subsequently spiked going block to block?  Thank you. 

JD

Sorry if the answer to this is obvious, but will a quick acting breaker on each of the variable lines trip when voltage is mismatched, bridged, and subsequently spiked going block to block?  Thank you. 

IMHO the answer really isn't obvious.
Based on real experience, I can tell you that the answer is sometimes.

I use Postwar Lionel #91 electromagnetic circuit breakers.

Whether they trip is based on how the circuit breaker is adjusted, and how far apart the voltage in the adjacent blocks are set. If the voltages are close, the breaker will not trip.

A magnetic breaker trips when the strength of the magnetic force exceeding the force exerted by a spring.   The megnetic force is determined by the ampere turns in the coil exerting the megnetic force.   The only impact that the voltage has on this is with resistive loads is that the voltage goes up, so does the current. E=IR. E is voltage, I is current, R is resistance. With the thremal breakers, the heat generated by power flowing through a bi-metallic element causes the breaker to open. The advantage of the thermal breaker is that it is heat that will damage the transformer. So a thermal breaker can be specified to match the increase in heat in the transformer.  Since it takes time for the heat to build up, the thermal breaker will allow high current loads for short periods of time.  This has the advantage of getting motors to start spinning, which are started by closing contacts and applying line voltage to start motors. Toy trains are subject to many short circuit situations due to the power being in exposed adjacent rails. It is desirable for toy train power supplies to be protected with magnetic breakers to quickly interrupt these short circuits.  But the transformer manufactures installed thermal breakers in the transformers to protect the transformer winding leaving it up to the toy train operator to provide circuit protection to protect the trains. In the postwar era Lionel provided the 91 circuit breaker for this.  Most operators never used any additional protected and survived to talk about it. The important thing is to never leave trains energized and unattended.  Now that trains are in the electronic era there are new protective devices and new problems. A whole new era. 

JD2035RR posted:

ADCX Rob posted:

chris a posted:

My question,  does one have the same inadvertent connection mis-matched voltage problem with a train crossing "Blocks" if the the (2) two block power sources are from the "A" throttle on two (2) different PW - ZW transformers ? ...

Yes, with regard to the damage potential to the equipment, but not to the secondary windings on the ZW.

Sorry if the answer to this is obvious, but will a quick acting breaker on each of the variable lines trip when voltage is mismatched, bridged, and subsequently spiked going block to block?  Thank you. 

JD

No. A magnetic, or other fast acting breaker, will only trip when the threshold current is exceeded in that circuit. 

TVS use is recommended to clamp voltage spikes.

You need two types of protection - one for over current, the other for over voltage.

 I use two P/W 275 watt ZW Transformers and they can put out 15 continuous amps. Nothing Chinese made today provides that type of power to the tracks that those old transformers did. Those ZW's are so durable and powerful, you can weld with one of them. Try that on the new stuff!

Dennis LaGrua posted:

 Nothing Chinese made today provides that type of power to the tracks that those old transformers did...

Except a TPC 300 or TPC 400.