This is one of ten transformers we have fabricated.  This unit is a 600W continuous duty plate transformer for a 23cm amplifier.  

Can WB7BST and WA7TZY turn this collection of stuff into a working plate transformer?  You bet they can, and here's how it's done. The kit shown to the left contains a pair of Silectron C cores, band clamps to hold them together, fish paper for insulation, a bobbin, miscellaneous mylar tapes, a collection of wires of the required sizes, and a can of air-cure transformer varnish.

The process of designing a power plate transformer is adequately described in older additions of the ITT Engineering Handbook.  We are going to leave out the math, and just concentrate on some of the physical aspects not evident in the math.  The first step is fabricating a bobbin for the transformer.  Our cores are 2" on a side.  A wooden mandrill, shown on the left, was cut from an odd section of 4" x 4" timber.  It is covered in Teflon tape.  Several other pieces of 1" x 2" (true dimensions) wood were also cut and covered in Teflon tape.  A suitable strip of fish paper is then wound around the mandrill and secured to itself with epoxy between the layers.  The finished bobbin is the gray object near the center of the picture.

This photo shows the mandrill being mounted in a winding lathe chuck (we had a lathe at our disposal for this project, however we have made and used hand winders fabricated from wood in the past).  The bobbin is slipped back over the mandrill, and the secondary winding is in the process of being "laid up".  Each layer of the secondary is separated from the previous layer by an overlapping wrap of Mylar tape.  The windings are then secured with yellow Mylar adhesive tape.  

When the winding process is complete, the bobbin is removed from the mandrill and the transformer C cores are inserted and secured together with stainless steel band clamps.  A set of 1" x 1" angle iron clamping brackets are made and attached to the transformer as a means of mounting it to the chassis.  The transformer is now complete and should be baked for about a day at 50°C.  Once baked, it's ready for varnish dip.

Here, the completed transformer is resting on a pair of cedar shims above a custom fabricated tank that contains the insulating varnish.  The tank is made of single sided circuit board soldered together with a 50W iron.  The transformer has been dipped for the first time, and the residual varnish is now draining back into the tank.  When dipping the transformer, allow it to remain in the varnish until the air bubbles cease to rise from the windings.  After the varnish cured for the first time (about a day) the transformer is dipped a second time and re-cured.  The varnish process should not be neglected, as it is an important means of providing additional insulation, mechanical strength, and perhaps most important, a means of keeping moisture from accumulating in the windings.

In this illustration, the core losses, copper losses, and excitation current are in the process of being verified.  This shows our completed transformer, now ready for the amplifier.