Nidec POWERDRIVE FX Series Installation Manual

Nidec POWERDRIVE FX Series Installation Manual Manual pdf 23 page image

23GENERAL EMC - HARMONICS - MAINS INTERFERENCEPOWERDRIVE FX Installation guide4729 en - 2017.08 / c4 - GENERAL EMC - HARMONICS -MAINS INTERFERENCEThe power structure of frequency inverters leads to theoccurrence of two types of phenomena:- Low-frequency harmonics fed back to the mains supply,- Emission of radio-frequency signals (RFI).These are independent phenomena. They have differentconsequences on the electrical environment.4.1 - Low-frequency harmonicsThe rectifier, at the head of the frequency inverter, generatesa non-sinusoidal AC line current.Courant de ligne consommé par un redresseur triphaséThis current carries harmonics with number 6n ± 1.The POWERDRIVE FX THDI level is less than 32%:significantly less than the maximum level defined by standardIEC 61000-3-12 (< 45%).4.2 - Radio-frequency interference:Immunity4.2.1 - GeneralThe immunity level of a device is defined by its ability to operatein an environment which is polluted by external elements orby its electrical connections.4.2.2 - StandardsEach device must undergo a series of standard tests(European standards) and meet a minimum requirement inorder to be declared as compliant with the variable speeddrive standards (EN 61800-3).4.2.3 - RecommendationsAn installation consisting exclusively of devices whichcomply with the standards concerning immunity is veryunlikely to be subject to a risk of interference.4.3 - Radio-frequency interference:Emission4.3.1 - GeneralFrequency inverters use high-speed switches (transistors,semi-conductors) which switch high voltages (around 550 V)and currents at high frequencies (several kHz). This providesbetter efficiency and a low level of motor noise.As a result, they generate radio-frequency (R.F.) signals whichmay disturb operation of other equipment or distortmeasurements taken by sensors:- Due to high-frequency leakage currents which escape toearth via the stray capacity of the drive/motor cable and thatof the motor via the metal structures which support the motor;- By conduction or feedback of R.F. signals on the power supplycable: conducted emissions;- By direct radiation near to the mains supply power cable orthe drive/motor cable: radiated emissions.These phenomena are of direct interest to the user.The frequency range concerned (radio frequency) does notaffect the energy supply company.4.3.2 - StandardsThe maximum emission level is set by the standards forvariable speed drives (EN 61800-3).4.3.3 - Recommendations• Experience shows that the levels set by the standards donot necessarily need to be observed to eliminate interferencephenomena.• Following the basic precautions described in section 4.5generally results in the correct operation of the installation.4.4 - Mains supply power4.4.1 - GeneralEach industrial power supply has its own intrinsic characteristics(short-circuit capability, voltage value and fluctuation, phaseimbalance, etc) and supplies equipment some of which candistort its voltage either permanently or temporarily (notches,voltage dips, overvoltage, etc). The quality of the mains supplyhas an impact on the performance and reliability of electronicequipment, especially variable speed drives.The POWERDRIVE FX is designed to operate with mainssupplies typical of industrial sites throughout the world.However, fo each installation, it is important to know thecharacteristics of the mains supply in order to carry outcorrective measures in the event of abnormal conditions.4.4.2 - Mains transient overvoltagesThere are numerous sources of overvoltages on an electricalinstallation:• Connection/disconnection of banks of power factor correctioncapacitors,• High-power thyristor-controlled equipment (oven, DC drive,etc),• Overhead power supply.4.4.2.1 - Connection/disconnection of a bank of cosjcorrection capacitorsConnecting power factor correction capacitors in parallel onthe drive power supply line when the drive is running cangenerate transient overvoltages that are likely to trip the drivesafety devices, or even damage it in extreme cases.If banks of power factor correction capacitors are used on thepower supply line, make sure that:• The threshold between steps is low enough to avoidcausing overvoltage on the line,• The capacitors are not permanently connected.