The Lionel Type ZW Transformer was the largest that was issued during the post war period and is listed at 275 watts. This transformer would operate four individual trains on four variable voltage circuits, however the two inner controls were usually used for accessories and these have no whistle or directional controls. Has both power and short circuit light indicators. The ZW has the same case as the Type VW, but internally it is completely different. Produced from 1948 until 1966, early units would have a Bakelite circuit breaker which is more reliable than the later produced wafer-type.

There are four variations:

Variation A: 250 watt available power produced in 1948-49.

Variation B: 275 watt available power. Earlier editions of this variation came with a bakelite circuit breaker. Reproduction bakelite circuit breakers are available. Produced 1950 to 1956.

Variation C: 275 watt available power. This is the ZW(R) variation. Although the exterior appears the same, major internal changes were made to this version to facilitate easier assembly. For the first few years this variation was manufactured, they were stamped on the bottom plate "ZW(R)." Produced 1957 until 1966.

Variation D: 275 watt available power. Los Angeles, California and Cleveland, Ohio had their own electrical statutes in place. To sell this transformer to these markets it was neccessary to receive the approval of these cites. Transformers sold during the period 1952 to 1958 in these cities were marked with a special decal on the bottom, and the boxes were over stamped with either an "LA" or "C." A premium is added to this variation for units whose decal matches the box over stamp.

This transformer is in great demand today and a premium is paid for clean housings.