11

MARCH 1994 - REVISED SEPTEMBER 1997

TISP2125F3, TISP2150F3, TISP2180F3

DUAL SYMMETRICAL TRANSIENT

VOLTAGE SUPPRESSORS

PRODUCT

INFORMATION

electrical characteristics

characteristic value will depend on the junction temperature at the instant of measurement. The values given

in this data sheet were measured on commercial testers, which generally minimise the temperature rise

caused by testing. Application values may be calculated from the parameters’ temperature curves, the power

dissipated and the thermal response curve (Zθ ).

lightning surge

wave shape notation

Most lightning tests, used for equipment verification, specify a unidirectional sawtooth waveform which has an

exponential rise and an exponential decay. Wave shapes are classified in terms of peak amplitude (voltage

or current), rise time and a decay time to 50% of the maximum amplitude. The notation used for the wave

shape is amplitude, rise time/decay time. A 50A, 5/310 µs wave shape would have a peak current value of

50 A, a rise time of 5 µs and a decay time of 310 µs. The TISP surge current graph comprehends the wave

shapes of commonly used surges.

generators

There are three categories of surge generator type, single wave shape, combination wave shape and circuit

defined. Single wave shape generators have essentially the same wave shape for the open circuit voltage

and short circuit current (e.g. 10/1000 µs open circuit voltage and short circuit current).

Combination

generators have two wave shapes, one for the open circuit voltage and the other for the short circuit current

(e.g. 1.2/50 µs open circuit voltage and 8/20 µs short circuit current) Circuit specified generators usually

equate to a combination generator, although typically only the open circuit voltage waveshape is referenced

(e.g. a 10/700 µs open circuit voltage generator typically produces a 5/310 µs short circuit current). If the

combination or circuit defined generators operate into a finite resistance the wave shape produced is

intermediate between the open circuit and short circuit values.

current rating

When the TISP switches into the on-state it has a very low impedance. As a result, although the surge wave

shape may be defined in terms of open circuit voltage, it is the current wave shape that must be used to

assess the required TISP surge capability. As an example, the CCITT IX K17 1.5 kV, 10/700 µs surge is

changed to a 38 A, 5/310 µs waveshape when driving into a short circuit. Thus the TISP surge current

capability, when directly connected to the generator, will be found for the CCITT IX K17 waveform at 310 µs

on the surge graph and not 700 µs. Some common short circuit equivalents are tabulated below:

Any series resistance in the protected equipment will reduce the peak circuit current to less than the

generators’ short circuit value. A 2 kV open circuit voltage, 50 A short circuit current generator has an

effective output impedance of 40

surge current requirement of the TISP becomes 31 A (2000/65) and not 50 A.

APPLICATIONS INFORMATION

STANDARD

OPEN CIRCUIT

VOLTAGE

SHORT CIRCUIT

CURRENT

CCITT IX K17

1.5 kV, 10/700 µs

38 A, 5/310 µs

CCITT IX K20

1 kV, 10/700 µs

25 A, 5/310 µs

RLM88

1.5 kV, 0.5/700 µs

38 A, 0.2/310 µs

VDE 0433

2.0 kV, 10/700 µs

50 A, 5/200 µs

FTZ R12

2.0 kV, 10/700 µs

50 A, 5/310 µs