Conformity Magazine - March 2009 - (Page 28) in each polarity under these conditions, GR-1089-CORE, Table 4-3 and Table 4-12. If repetitive impulse testing causes component damage and it does not operate properly as required in GR-1089-CORE, Section 4.6.1, then the component has failed Protection Coordination. Figure 6 shows the test set-up for impulse coordination. • Coordination surge generator: The impulse generators used are specified in Table 7. These generators are not specified for short-circuit current, but for the current delivered into the highest primary limiting voltage category of 1000 V. • Optional voltage limiter: GR-1089-CORE, Issue 4 wasn’t thoroughly proofed before project termination. One result was the coordination procedure doesn’t address changes in component values under the impulse repetitions. Increases in resistance will cause the voltage to rise above the category level and possibly lead to component failure. This situation is unrealistic and could have been avoided by leaving the category voltage limiter in place for the repetitive testing. UL 2564 fixes this oversight and allows a voltage limiter to be used in repetitive testing. If the voltage limiter starts to conduct, the generator voltage is reduced to reach the coordination condition again. • Component voltage and current recorder: This is the same equipment as used for the AC testing. • Any primary series resistance: Where an agreed primary has a specified series resistance from wire input to output, the equivalent resistance or component used in the primary is connected in series with the overcurrent protector. • Mounted component: This is the same arrangement as used for the AC testing. First, the generator voltage, Vg, for the repetitive impulse tests must be determined. The procedure for finding the value of Vg is shown in Figure 7. Once Vg is established, the repetitive testing can be done as described. Table 7 lists the surge generators needed for coordination testing. Summary Designers wanting certainty of overcurrent protector performance under equipment standard stresses should specify UL 2564 recognition. Components recognized to the appropriate tests of 2564 will effectively be pre-tested to the required end-product safety requirements of fire, electrical shock, and fragmentation injury. For some standards, withstand criteria will be verified. Figure 7: Procedure for determining the coordination generator voltage 28 Conformity marCh 2009 Figure 6: Impulse coordination test set-up FAST Link www.conformity.com/2740 http://www.conformity.com/2740
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