Industry Magazine Commercial Kitchen Fall 2016 | Page 7

THE TROUBLE WITH TRANSFORMERS

David Duckworth
David Duckworth is the Director of Training and
Development at Commercial Kitchen Parts &
Service in San Antonio, Texas.

THE TROUBLE
WITH
TRANSFORMERS

What To Do When Your Transformer Fails
YOU have just found that the
transformer on a piece of equipment
is not producing any voltage on the
secondary side, also known as the load
side. You check the primary side and
you find the correct voltage supply. So
you install a new transformer and you’re
done, right?

WRONG! You will probably be
replacing the new transformer
immediately!
A transformer typically does not
fail on its own; some other situation

the windings, and the transformer
eventually burns out, or as we say in the
business, “smokes.”
Another reason the transformer may
fail is contamination. The transformer
can be in a wet or corrosive environment,
which may also lead to a breakdown in
the insulation of the windings.
Your first step before replacing the
transformer is to check the circuitry
for any signs of a short circuit to ground
and use your ohmmeter to inspect all
magnetic coils on contactors, relays, and
solenoid valves for any breakdown in

to find the problem. Disconnect each
component powered by the transformer.
Reapply power to the transformer and
confirm you have power out of your
secondary side. Then start to reconnect
each component until the fuse blows.
The last part you connect is generally
the cause of the transformer failure,
and that component will also need
to be replaced before replacing the
transformer. Remember, it is cheaper
to replace a few fuses than a few
transformers!
To properly fuse the transformer for

“THE MAJORITY OF TRANSFORMERS FAILURES CAN BE ATTRIBUTED TO EXCESSIVE
OVERLOADS DUE TO A SHORT CIRCUIT ON THE SECONDARY, OR LOAD, SIDE OF THE
TRANSFORMER.”
or component has caused it to fail.
You need to find that problem before
changing the transformer.
The majority of transformer failures
can be attributed to excessive overloads
due to a short circuit on the secondary,
or load, side of the transformer.
When this load increases, it produces
excessive heat beyond the capability
of the transformer. This heat buildup
breaks down the insulation between

FALL 2016

resistance. If there is an obvious shorted
wire or coil, first correct the problem
and then install the new transformer.
If you are not sure what caused the
transformer to fail, you will need to
temporarily fuse the new transformer.
An in-line fuse holder will need to
be installed in-line with the hot wire
coming off the secondary side of the
transformer. Use only fast-blow fuses.
You will use a process of elimination

the load capability, take the VA rating of
the transformer and divide it by the side
you are trying to protect.
Examples:
Primary side 60 VA ÷ 120 volts =
.50 = ½-amp fuse.
Secondary 60 VA ÷ 24 volts =
2.5 = 2½-amp fuse.
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