Nidec Unidrive M600 Series Design Manual

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Nidec Unidrive M600 Series Design Manual Manual pdf 10 page image

Safetyinformation Introduction ProductInformationSystemdesignMechanicalInstallationElectricalInstallationGettingstarted Optimization Parameters TechnicaldataComponentsizing Diagnostics ULInformation10 Unidrive M Regen Design GuideIssue Number: 42 IntroductionThe following Design Guide should be read in conjunction with therelevant Unidrive M Control User Guide and Power Installation Guide.Any Unidrive M600/M700/M701 drive can be configured as an ACRegenerative Unit (hereafter referred to as a Regen drive).It is possible to operate a Unidrive M702 in Regen Mode although it isnot recommended due to the lack of control connections required to fullysupport Regen operation.This Design Guide gives instructions for the drive connected to thesupply. For instructions regarding the drive connected to the motor,please refer to the relevant Unidrive M Control User Guide and PowerInstallation Guide.This guide covers the following:• Principles and advantages of operation in Regen mode• Safety information• EMC information• Detailed information on additional components required• System design• Special considerations• Installation• Commissioning and optimization of the completed systemAt least two Unidrive M drives are required to form a completeregenerative system - one connected to the supply and the second oneconnected to the motor. A Unidrive M in Regen mode converts the ACmains supply to a controlled DC voltage, which is then fed into anotherdrive(s) to control a motor(s).The motoring drive(s) in a Regen configuration could be another driveother than a Unidrive M, e.g. Unidrive SP or Commander SK etc.The following Regen components are also required in addition to theUnidrive M drives.1. Regen inductor2. Switching frequency filter inductor3. Switching frequency filter capacitor4. Softstart resistor5. Varistors6. MCBs7. Overload relays2.1 Regen operationFor use as a regenerative front end for four quadrant operation.Regen operation allows bi-directional power flow to and from the ACsupply. This provides far greater efficiency levels in applications whichwould otherwise dissipate large amounts of energy in the form of heat ina braking resistor.The low frequency harmonic content of the input current is negligible dueto the sinusoidal nature of the waveform when compared to aconventional bridge rectifier or thyristor front end.2.2 Advantages of Unidrive M operating inRegen modeThe main advantages of an AC Regen system are:• Energy saving.• The input current waveform is sinusoidal.• The input current has a near unity power factor.• Harmonic reduction feature.• The output voltage for the motor can be higher than the available ACmains supply.• Possible to control reactive current or power (kVAr units).• The Regen drive will synchronize to any frequency between 10 and200 Hz, provided the supply voltage is within the supplyrequirements (operating frequency range of 45 Hz to 66 Hz) refer tosection 6.2 Supply requirements on page 117.• It is possible to configure the drive to continue operating for shortperiods of time during supply dips and faults i.e. ride through.• Island detection feature to prevent unwanted islanded operation,where part of the power distribution network becomes separatedfrom the power grid and is unintentionally maintained by an inverter.• The Regen and motoring drives are identical (when usingUnidrive M).• Power feed-forward term available, using analog I/O set-up or fastsynchronous communications.• A fast transient response is possible using the power feed forwardterm.• Voltage and frequency limits configurable.2.3 Principles of operationThe input stage of a non-regenerative AC drive is usually anuncontrolled diode rectifier, therefore power cannot be fed back onto theAC mains supply. By replacing the diode input rectifier with a voltagesource PWM input converter (Unidrive M), AC supply power flow can bebi-directional with full control over the input current waveform and powerfactor. Currents can now be controlled to give near unity power factorand a low level of line frequency harmonics.In the case of a Unidrive M operating in regenerative mode, the IGBTstage is used as a sinusoidal rectifier converting the AC supply to acontrolled DC voltage.Furthermore, by maintaining the DC bus voltage above the peak supplyvoltage the load motor can be operated at a higher speed without fieldweakening. Alternatively, the higher output voltage available can beexploited by using a motor with a rated voltage higher than the AC mainssupply, thus reducing the current for a given power.The difference between the PWM line voltage and the supply voltageoccurs across the Regen inductors at the Regen drive. This voltage hasa high frequency component, which is blocked by the Regen inductor,and a sinusoidal component at line frequency. As a result currentsflowing in these inductors are sinusoidal with a small high frequencyripple component.Regen inductors must be used to ensure a minimum source impedance,these being selected and specified later in the guide.Safe Torque Off functionThe drive enable input is designed to offer the Safe TorqueOff safety function only when the drive is connected directlyto the motor. The enable input for the drive which isconnected to the AC supply works only as a simple enableinput for regenerative operation. It does not prevent powerfrom reaching the motor and it does not offer the Safe TorqueOff safety function. No attempt must be made to use it for asafety function. Failure to observe this warning could result adangerous failure of a machinery safety function.Any reference in this Design Guide to Safe Torque Off shouldbe taken to refer only to the enable function and not to anysafety function.WARNINGNOTENOTE