Nidec POWERDRIVE FX Series Installation Manual

Nidec POWERDRIVE FX Series Installation Manual Manual pdf 24 page image

24GENERAL EMC - HARMONICS - MAINS INTERFERENCEPOWERDRIVE FX Installation guide4729 en - 2017.08 / c4.4.2.2 - Presence of commutation notches on the lineWhen high-power thyristor-controlled equipment is connectedon the same line as the drive, it is essential to ensure that theharmonics generated by the commutation notches do notexcessively distort the mains voltage and do not create voltagepeaks with amplitude higher than 1.6 x mains Vrms. If this isthe case, it is essential to take corrective measures toguarantee the mains quality.4.4.2.3 - Overhead power supplyAn overhead power supply is not allowed for thePOWERDRIVE FX.4.4.3 - Mains short-circuit powerAs with all variable speed drives, the mains short-circuitpower to which the POWERDRIVE FX is connected has aneffect on its behaviour. Notably, when the mains short-circuitpower is low, voltage oscillations may appear due toresonances between the inductive impedance of the mainsand the filtering capacity of the POWERDRIVE FX. To avoidthe POWERDRIVE FX tripping because of these oscillations,make sure that the ratio R sc = Isc /(n x I LM) is higher than 50.Where:I sc : Mains short-circuit current at the point of connectionn: Number of POWERDRIVE FX drives connected on thesame power supply lineI L M: POWERDRIVE FX rated input currentAs a matter of course, check that:• The sum of the power of all POWERDRIVE FX drivesconnected to the same transformer does not exceed 35% ofthe total transformer rated power.• The sum of the power of the POWERDRIVE FX drivesinstalled on a generator does not exceed 20% of its ratedpower.4.4.4 - Ground connectionsThe earth equipotential of some industrial sites is not alwaysobserved. This lack of equipotential leads to leakage currentswhich flow via the earth cables (green/yellow), the machinechassis, the pipework, etc, and also via the electricalequipment. In some extreme cases, these currents can tripthe drive.It is essential that the earth network is designed andimplemented by the installation supervisor so that itsimpedance is as low as possible, so as to distribute the faultcurrents and high-frequency currents without them passingthrough electronic equipment.Metal grounds must be mechanically connected to each otherwith the largest possible electrical contact area. Under nocircumstances can the earth connections designed to protectpeople, by linking metal grounds to earth via a cable, serve asa substitute for the ground connections (see IEC 61000-5-2).The immunity and radio-frequency emission level are directlylinked to the quality of the ground connections.4.5 - Basic precautions for installationThese are to be taken into account when wiring the cabinetand any external components. In each paragraph, they arelisted in decreasing order of effect on correct operation of theinstallation.4.5.1 - Wiring inside the cabinet- Do not run the control cables and the power cables in thesame cable ducts.- For control cables, use shielded twisted cables.4.5.2 - Wiring outside the cabinet- Connect the motor earth terminal directly to that of thedrive.It is recommended that a shielded symmetrical cable is used:three phase conductors and coaxial or symmetrical PEconductor and shielding.A separate PE protective conductor is mandatory if theconductivity of the cable shielding is less than 50% of theconductivity of the phase conductor.- The shielding must be connected at both ends: drive endand motor end (completely connected).- In the second industrial environment, the shielded motorpower supply cable can be replaced by a 3-core + earth cableplaced in a fully enclosed metal conduit (metal cable duct forexample). This metal conduit must be mechanically connectedto the electrical cabinet and the structure supporting the motor.If the conduit consists of several pieces, these should beinterconnected by braids to ensure earth continuity. The cablesmust be fixed securely at the bottom of the conduit.- There is no need to shield the power supply cables betweenthe mains supply and the drive.- Isolate the power cables from the control cables. The powercables must intersect the other cables at an angle of 90°.- Isolate sensitive elements (probes, sensors, etc.) from metalstructures which may be shared by the motor support.