V
OLTECH
AC
I
NTERFACE
U
SER
M
ANUAL
98-072
ISS
7
PAGE
56
7.4. C
OMPLIANCE WITH
EN954
The AC Interface meets the requirements of category 3 of EN954 (safety-related parts for control systems),
and as such will protect against most faults associated with high-voltage AC sources.
Should any single part fail in the AC Interface Fixture, there will be no loss of the safety system function.
Of the three test modes, maximum protection is afforded to the high-power generator (used for the step-up or
step-down transformer test mode), where the system will meet category 4 of EN954.
EN954 Category 4
This category defines that any single fault occurring within the safety system will not cause loss of the safety
function, and any single fault will be detected before a second fault could occur creating a loss in the safety
function.
The AC Interface Fixture will comply with a category 4 system when using an output transformer that is
energised by a source within the AT3600/AT5600 along with a Voltech approved safety system, because the
Voltech safety system guarantees that the connection to the output transformer is disconnected, when the
interlock is broken.
EN954 Category 3
This category defines that any single fault occurring within the safety system will not cause loss of the safety
function and recommends that, when possible, any single fault will be detected before a second fault could
occur creating a loss in the safety function, although this is not mandatory.
As an extra precaution in this case, if the system is rendered unsafe, there must be a high probability that the
user can avoid the hazard.
The Voltech AC Interface will always meet category 3, if connected correctly to an external AC source, as
described in this manual.
The AC Interface Fixture has been designed so that any single fault will not render the system unsafe and, if
multiple faults occur, a clear indication will be given to the user if dangerous voltages are present after testing
a wound component
