Operation Manual

08/ 2012 16 / 58
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BENNING ST 750 A
2
If for the stated insulating resistance measurements for protection class I or II
- not all parts are measured completely (e.g. if relays or semiconductor components impede the transmission of electricity) or
- if the measurements have been terminated with a negative result for devices containing heating elements,
the alternative leakage current measurement method must not be applied!
In this case, it is necessary to use the direct or differential current measurement method.
3
Additional tests for devices with a secondary output voltage, e.g. isolating transformer, chargers, converters, mains supply units:
1. insulating resistance measurement between secondary and primary side
2. insulating resistance measurement between secondary side and the equipment body
 3. contactcurrentmeasurementsofthesecondaryvoltageoutputs(exceptSKIII)
4. measurement of the open-circuit voltage / output voltage.
4
 Whenexceedingthelimitingvalue(protectiveconductorcurrent),ithastobecheckedwhetherotherlimitingvalueshavetobeobservedduetoproductstandardsormanufacturerspecications.