ITT - Index of

SELENIUM TRANSIENT VOLTAGE SUPPRESSORS
HOW TO SELECT THE PROPER RECTIFIER
Determination of Current Rating
Although the peak value and duration
of a transient current cannot
always be determined, certain
valid assumptions can be made to
determine the ITT suppressor rectifier
current rating for the application.
For circuits in which a transformer
is the power source, usually the
greatest transient currents have
been observed when the circuit is
interrupted with no load on the
transformer. The transient current
is the magnetizing current of the
transformer. If the actual transient
current is not known, a valid assumption
can be made by the use
of the magnetizing current versus
voltage on page 4. If the transient
results from opening a circuit containing
an inductance, the transient
current will be the current
through the inductance at the instant
of interruption. To select the
proper ITT suppressor series, assume
a single pulse width of 4
milliseconds and refer to the pulse
current versus time curve on page
4: The same curve can be used to
select the appropriate ITT series
when a single pulse width other
than 4 milliseconds is known or
assumed.
Voltage Rating
After the required current rating
has been established, determine
the maximum steady-state voltage
which will appear across the suppress?r
rectifier and select the appropriate
type number from the
tables on pages 2 and 3. Note that
both RMS and peak voltage ratings
are tabulated for AC types and DC
ratings for DC types. Use the RMS
value for. sinusoidal voltages'
otherwise, use the peak value of
the input voltage to select the
proper rectifier.
Zener Voltage
The Zener voltages shown in the
characteristics tables are the maxi~um
instantaneous voltages that
will appear across the rectifier if
the 4 millisecond current rating
is not e~c.eeded. Any ITT suppress