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Industrial Control Transformers
Application
57
08/2005
© 1999–2005 Schneider Electric All Rights Reserved
Technical Data
50/60 Hertz
Transformers that are dual rated for 50/60 Hz are truly global units and no derating is required for
voltages or VA. (Type T are 50/60 Hz; Type EO are 60 Hz with de-rating for 50 Hz).
Base Plates
The development of welded cores has allowed the incorporation of base plates on larger VA
transformers. Base plates are usually welded to the core of the transformer for a solid connection to
the transformer. They allow manufacturers to offer more standardized mounting for specific VA sizes
by allowing multiple core stacks. Available for Type T transformers only.
Touch-Safe Terminals
Being able to offer touch-safe terminals is increasing in importance. Currently all equipment that must
comply with EN 60-204 (Machine and Low Voltage Directives) must have some type of barrier for live
parts. Besides the CE standard listed above, domestic customers are requiring barriers on live parts
with voltages above 460 V. These customers allow Plexiglas™ covers to be installed for these barriers.
Type T transformers can be made Fingersafe
®
by using snap-on covers that are removable with a
screwdriver or other flat tool. Covers are sold separately.
Formed Terminal Board
Formed terminal boards are used on multiple VA ranges and different voltage combinations. This
allows the manufacturer to punch jumpers for customer interconnections and gives the customer the
same basic layout for all units. The snap-on covers for touch-safe terminations also are available on
units with formed terminal boards. Available for Type T transformers only.
Varnish Vacuum Impregnation
This is a manufacturing process for the core and coil of industrial control transformers. The transformer
is put into a tank of varnish, then the varnish is put into a vacuum, causing the varnish to be forced
throughout the coil and core. After being vacuum impregnated, the units are cured in an oven to seal
the varnish. The varnish is absorbed by any paper insulation system and coats other insulation with
another layer of electrical strength. The process causes the coil to have a very tight connection
because it is completely bonded and mechanically very strong. The cores are also tightly bonded with
the varnish, causing the units to have better heat transfer and less vibration noise.
Schneider Electric uses this process on all control transformers, using a clear varnish with optimum
electrical characteristics.