Transformer Ballast Page
| Transformers which do not self current limit i.e pole pigs or potential transformer need to have external current limiting, this can be achieved by the use of inductors or resistors, we have gone down the inductor route. The picture below show our twin coil ballasts. It is made up of a standard E, I core with a coil of thick wire wound around the two outside legs of the core. |
|
The core laminates are 50mm by 50mm silicon steel. The core also has plastic spacers inserted between the E and the top I core. This is used to fine-tune the current limiting. As there are two coils they can be wired in three ways. i-One coil in series ii-Two coils in series iii-Two coils in parallel With each different combination a different level of current control is achieved |
The picture on the right show the white plastic inserts much better. The two long threaded rods on the top holds the I core to the E core. Below are two pictures of the box that now houses the ballast and the switch and its entire wiring layout |
|
|
|
| As you can see the wiring for the switch
is quite complex and was arranged and built by Steve
Bell, The switch is a 240vac/40A 4-pole, 4-way rotary
switch, which was bought from display electronics. This
system now does away with the arc welder that we were
using before, and keeps all the wiring out of the way and
reduces all the plugs and leads that we used before. With
this switched supply we can limit form 7A (two coils in
series) 16A (one coil) 32A (both coils in parallel), we
tested the ballast with our new JACOBS LADDER. Below is a wiring diagram for the switch. |
|
