AKD™ Installation Manual - TG Drives

AKD Installation | 6 Technical description and data6.18 Shock-hazard Protection6.18.1 Leakage CurrentLeakage current via the PE conductor results from the combination of equipment and cable leakage currents.The leakage current frequency pattern includes a number of frequencies, whereby the residual-current circuitbreakers definitively evaluate the 50 Hz current. For this reason, the leakage current cannot be measuredusing a conventional multimeter.As a rule of thumb, the following assumption can be made for leakage current on our low-capacity cables at amains voltage of 400 V, depending on the clock frequency of the output stage:I leak= n x 20 mA + L x 1 mA/m at 8 kHz clock frequency at the output stageI leak= n x 20 mA + L x 2 mA/m at a 16 kHz clock frequency at the output stage(where Ileak=leakage current, n=number of drives, L=length of motor cable)At other mains voltage ratings, the leakage current varies in proportion to the voltage.Example: 2 x drives + a 25m motor cable at a clock frequency of 8 kHz:2 x 20 mA + 25 m x 1 mA/m = 65 mA leakage current.Since the leakage current to PE is more than 3.5 mA, in compliance withIEC61800-5-1 the PE connection must either be doubled or a connecting cablewith a cross-section >10 mm² must be used. Use the PE terminal and the PE connectionscrews in order to fulfill this requirement.The following measures can be used to minimize leakage currents:• Reduce the length of the engine cable.• Use low-capacity cables (see page 41).6.18.2 Residual Current Protective Device (RCD)In conformity with IEC 60364-4-41 – Regulations for installation and IEC 60204 – Electrical equipment ofmachinery, residual current protective devices (RCDs) can be used provided the requisite regulations are compliedwith.The AKD is a 3-phase system with a B6 bridge. Therefore, RCDs which are sensitive to all currents must beused in order to detect any DC fault current. Refer to the chapter above for the rule of thumb for determiningthe leakage current.Rated residual currents in the RCDs:10 to 30 mA Protection against "indirect contact" (personal fire protection) for stationary and mobile equipment,as well as for "direct contact".50 to 300 mA Protection against "indirect contact" (personal fire protection) for stationary equipmentRecommendation: In order to protect against direct contact (with motor cablesshorter than 5 m) Kollmorgen recommends that each drive be protected individuallyusing a 30 mA RCD which is sensitive to all currents.If you use a selective RCD, the more intelligent evaluation process will prevent spurious tripping of the RCD.60 Kollmorgen | December 2009