TISP7xxxF3 (MV, HV) Overvoltage Protector Series
APPLICATIONS INFORMATION
Lightning Surge (continued)
ITU-T 10/700 Generator (continued)
The series resistance from C to an individual output is 2 x 27.5 = 55 Ω, giving an output conductance of 18 A/kV. For each 1 kV of capacitor
1
charge voltage, 18 A of output current will result.
At 25 °C, these protectors are rated at 70 A for the single terminal pair condition and 95 A for the dual condition (R and G terminals and T and
G terminals). In terms of generator voltage, this gives a maximum generator setting of 70 x 40 = 2.8 kV for the single condition and 2 x 95 x
27.5 = 5.2 kV for the dual condition. The higher generator voltage setting for the dual condition is due to the current waveform decay being
shorter at 250 µs compared to the 310 µs value of the single condition.
Other ITU-T recommendations use the 10/700 generator: K.17 (11/88) “Tests on power-fed repeaters using solid-state devices in order to
check the arrangements for protection from external interference” and K.21(10/96) “Resistibility of subscriber’s terminal to overvoltages and
overcurrents”, K.30 (03/93) “Positive temperature coefficient (PTC) thermistors”.
Several IEC publications use the 10/700 generator; common ones are IEC 6100-4-5 (03/95) “Electromagnetic compatibility (EMC) - Part 4:
Testing and measurement techniques - Section 5: Surge immunity test” and IEC 60950 (04/ 99) “Safety of information technology equipment”.
The IEC 60950 10/700 generator is carried through into other “950” derivatives. Europe is harmonized by CENELEC (Comité Européen de
Normalization Electro-technique) under EN 60950 (included in the Low Voltage Directive, CE mark). US has UL (Underwriters Laboratories)
1950 and Canada CSA (Canadian Standards Authority) C22.2 No. 950.
FCC Part 68 “Connection of terminal equipment to the telephone network” (47 CFR 68) uses the 10/700 generator for Type B surge testing.
Part 68 defines the open circuit voltage wave shape as 9/720 and the short circuit current wave shape as 5/320 for a single output. The current
wave shape in the dual (longitudinal) test condition is not defined, but it can be assumed to be 4/250.
Several VDE publications use the 10/700 generator, for example: VDE 0878 Part 200 (12/92) ”Electromagnetic compatibility of information
technology equipment and telecommunications equipment; Immunity of analogue subscriber equipment”.
1.2/50 Generators
The 1.2/50 open circuit voltage and 8/20 short circuit current combination generator is defined in IEC 61000-4-5 (03/95) “Electromagnetic
compatibility (EMC) - Part 4: Testing and measurement techniques - Section 5: Surge immunity test”. This generator has a fictive output
resistance of 2 Ω, meaning that dividing the open circuit output voltage by the short circuit output current gives a value of 2 Ω(500 A/kV).
The combination generator has three testing configurations; directly applied for testing between equipment a.c. supply connections, applied
via an external 10 Ω resistor for testing between the a.c. supply connections and ground, and applied via an external 40 Ω resistor for testing
all other lines. For unshielded unsymmetrical data or signalling lines, the combination generator is applied via a 40 Ω resistor either between
lines or line to ground. For unshielded symmetrical telecommunication lines, the combination generator is applied to all lines via a resistor of
n x 40 Ω, where n is the number of conductors and the maximum value of external feed resistance is 250 Ω. Thus, for four conductors, n = 4
and the series resistance is 4 x 40 = 160 Ω. For ten conductors, the resistance cannot be 10 x 40 = 400 Ω and must be 250 Ω. The combina-
tion generator is used for short distance lines; long distance lines are tested with the 10/700 generator.
When the combination generator is used with a 40 Ω, or more, external resistor, the current wave shape is not 8/20, but becomes closer to the
open circuit voltage wave shape of 1.2/50. For example, a commercial generator when used with 40 Ω produced an 1.4/50 wave shape.
The wave shapes of 1.2/50 and 8/20 occur in other generators as well. British Telecommunication has a combination generator with 1.2/50
voltage and 8/20 current wave shapes, but it has a fictive resistance of 1 Ω. ITU-T recommendation K.22 “Overvoltage resistibility of equip-
ment connected to an ISDN T/S BUS” (05/95) has a 1.2/50 generator option using only resistive and capacitive elements, Figure 34.
The K.22 generator produces a 1.4/53 open circuit voltage wave. Using 25 Ω output resistors, gives a single short circuit current output wave
shape of 0.8/18 with 26 A/kV and a dual of 0.6/13 with 20 A/kV. These current wave shapes are often rounded to 1/20 and 0.8/14.
MARCH 1994 - REVISED MARCH 2006
Specifications are subject to change without notice.
Customers should verify actual device performance in their specific applications.
BOURNS [ BOURNS ELECTRONIC SOLUTIONS ]
