Sidactor Protection Thyristor Products Page 64 SIDACtor Protection Thyristor Products

SIDACtor Protection Thyristors 2017 Littelfuse, Inc. Specifications are subject to change without notice. Revised: 02/23/17 Overvoltage Flowchart The overvoltage flowchart in Figure 3.19 shows specific guidelines for determining overvoltage requirements applicable to telcom applications that use outside cable exposed to power line fault conditions. These overvoltage events can be the result of a) contact with a multi-earthed neutral distribution power line (4 kV to approximately 50 kV), b) induction from a distribution power line fault to earth, c) EPR (earth potential rise) due to power line fault current flowing to earth, and d) contact with 120 V power line. The worse case protection for inside wiring with 3-mil carbon blocks can result in a maximum longitudinal voltage of 600 V. Asymmetrical operation of these carbon blocks result in transverse (differential or metallic) voltages up to this 600 V. Furthermore, a high impedance power line fault to earth can result in a maximum induced current of 2.2A. Induction or EPR events can cause a maximum current event of 7A enduring for up to 5 S. A power line contact with a shielded telephone cable can result in an I 2 t of 2,400 A 2 -S. A 40 A, 1.5 S event is considered the worst case. A 120 V power line cross with a telephone line can deliver up to 25 A to the telephone wiring, limited by the wiring impedance. No Yes 100 A 2 -s limiting 1 No Overvoltage Testing! Connects to Outside Cable? Yes 1.3 A Limiting? line cord smaller or equal to 26 AWG? Yes Pass 1? Yes Pass 6.1.21? 1) FIRE ENCLOSURE & SPACING Yes Acceptable! FIRE ENCLOSURE? No Yes Pass 5? Pass 2? 2) Pass 3,4? 3) Yes No Yes Not Acceptable! Notes: 1) The telephone line is adequately isolated from earth for the operating mode being considered at a voltage of 120 V. 2) Test Condition 2 is not required for equipment containing a method for limiting current to 1.3 A max steady state (e.g., a fuse rated 1.0 A maximum). 3) Test Conditions 3 and 4 are not required for equipment whose application (because of system function, design limitations, etc.) is limited to connections to outside cable not exceeding 1,000 m (for example, equipment that connects to ISDN S/T reference points and certain proprietary telephone sets). Figure 3.19 Overvoltage Flowchart Table 3.53 UL 60950 Overvoltage Test Figure 3.20 Metallic Connection Appearances The questions "Passes 1, 2, 3, 4, and 5" shown in Figure 3.19 refer respectively to Tests L1 and M1, L2 and M2, L3 and M3, L4 and M4, and L5 shown in Table 3.53. These tests are designed to simulate the following: Contact with primary power Short-term induction as a result of a primary power fault to a multi-earth neutral Long duration power fault to Ground Direct contact between the power mains and a telecommunications cable Test Voltage (V RMS ) Current (A) Time Comments L1 600V 40 1.5 s L2 600V 7 5 s L3 600V 2.2 See Note 2 Reduce to 135% fuse rating L4 See Note 1 2.2 See Note 2 Reduce to 135% fuse rating L5 120V 25 See Note 2 M1 600V 40 1.5 s M2 600V 7 5 s M3 600V 2.2 See Note 2 Reduce to 135% fuse rating M4 See Note 1 2.2 See Note 2 Reduce to 135% fuse rating Notes: 1 Voltage < conduction voltage of protection 2 Test for 30 minutes or until an open circuit occurs unless it appears possible that risk of fire or safety hazard may result; then continue test until ultimate results are obtained (maximum 7 hours). General Notes: - ISDN S/T interface only L1, L2, L5, M1, and M2. - If Test 3 resulted in open condition, bypass the fuse, reduce current to 135% of the fuse rating and continue the test. - L4 and M4 are conducted at a voltage level just below Vs only if SIDACtor VS 285 V S . - For test conditions M1, L1, M5, and L5 a wiring simulator (MDL 2 A fuse) is used. - Compliance means no ignition or charring of the cheesecloth, and/or wiring simulator does not open. - Tests 2, 3, and 4 are required only if the unit is not a fire enclosure. - EUT shall continue to comply with the requirements of Clause 6.2 (Separation requirements and Electric strength requirements) at the conclusion of these overvoltage tests. Equipment Under Test Telecommunication Network Connection Points Secondary Protector Simulator or Wiring Station Timed Switch Current Limiting Resistor Variable Voltage Source Equipment Earth Figure 3.21 Longitudinal Connection Appearances Equipment Under Test Secondary Protector Simulators or Wiring Stations Timed Switch Equipment Earth Current Limiting Resistors Variable AC Voltage Source Regulatory Requirements (continued)

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