Nidec Digitax ST Series Installation Manual

Nidec Digitax ST Series Installation Manual Manual pdf 30 page image

30 Digitax ST Installation GuideIssue: 74.5 Ground leakageThe ground leakage current depends upon whether the internal EMC filter is installed.The drive is supplied with the filter installed. Instructions for removing the internal filterare given in Figure 4-3.With the internal EMC filter fitted the ground leakage current is as follows:Table 4-3 Ground leakage current with internal EMC filter installedWith internal EMC filter removed the ground leakage current = <1 mA.4.5.1 Use of residual current device (RCD)There are three common types of ELCB / RCD:1. AC - detects AC fault currents2. A - detects AC and pulsating DC fault currents (provided the DC current reacheszero at least once every half cycle)3. B - detects AC, pulsating DC and smooth DC fault currents• Type AC should never be used with drives• Type A can only be used with single phase drives• Type B must be used with three phase drivesIf an external EMC filter is used, a delay of at least 50 ms should be incorporated toensure spurious trips are not seen. The leakage current is likely to exceed the trip levelif all of the phases are not energized simultaneously.4.6 EMC4.6.1 Internal EMC filterIt is recommended that the internal EMC filter is kept in place unless there is a specificreason for removing it.Special attention is required when using a DST120X model on an ungrounded supply(IT supply). In the event of a ground fault in the motor circuit the drive may not trip andthe filter could be overstressed. In this case, either the filter must be removed oradditional independent motor ground fault protection must be provided.The internal EMC filter reduces radio-frequency emissions into the mains supply. Wherethe motor cable is short, it permits the requirements of EN 61800-3:2004 to be met forModel3 phase Starground3 phase Deltaground 1 phasemADST120X at 220V 4 10 3DST140X at 400V 12 40The above leakage current is just the leakage current of the drive with the internal EMC filterconnected and does not take into account any leakage currents of the motor or motor cable.NOTEIn both cases, there is an internal voltage surge suppression device connected toground. Under normal circumstances, this carries negligible current.NOTEWhen the internal EMC filter is installed, the leakage current is high. In this case, apermanent fixed ground connection must be provided with a cross sectional area equalto 10 mm2 .WARNINGOnly type B ELCB / RCD are suitable for use with 3 phase inverter drives.WARNING