
100.210-IOM (FEB 2015)
Page 11
VYPER
™
VARIABLE SPEED DRIVE
INSTALLATION - OPERATION - MAINTENANCE
HARMONIC FILTER
The.VSD.system.may.include.an.harmonic.filter.designed.to.
meet.the.IEEE.Std.519.-1992,.“IEEE.Recommended.Practices.
and.Requirements.for.harmonic.Control.in.Electrical.Power.
Systems”..The.filter.is.offered.as.a.means.to.“clean.up”.the.
input.current.waveform.drawn.by.the.VSD.from.the.power.
mains,.thus.reducing.the.possibility.of.causing.electrical.inter-
ference.with.other.sensitive.electronic.equipment.connected.
to.the.same.power.source.
Figure.3.is.a.plot.of.the.typical.input.current.waveform.for.the.
VSD.system.without.the.harmonic.filter.when.the.system.is.
operating.at.50%.load..Figure.4.is.a.plot.of.the.typical.input.
current.waveform.for.the.VSD.system.with.the.harmonic.filter.
installed. when. operating. at. the. same. load. conditions.. The.
plots.show.that.the.input.current.waveform.is.converted.from.
a.square.wave.to.a.fairly.clean.sinusoidal.waveform.when.the.
filter.is.installed..In.addition,.the.power.factor.of.the.system.
with.the.harmonic.filter.installed.corrects.the.system.power.
factor.to.nearly.unity.
The.power.section.of.the.harmonic.Filter.is.composed.of.four.
major.blocks:.a.precharge.section,.a.“trap”.filter.network,.a.
three.phase.inductor.and.an.IGBT.Phase.Bank.Assembly...See.
the.elementary.wiring.diagram.in.Figures.5A.and.5B.for.wiring.
and.component.reference
The Precharge Section
.is.formed.by.three.resistors.(11RES.
-.13RES).and.two.contactors,.the.precharge.contactor.(2M),.
and.the.supply.contactor.(3M)..The.precharge.network.serves.
two.purposes,.to.slowly.charge.the.DC.link.filter.capacitors.
associated. with. the. filter. Phase. Bank. Assembly. (via. the.
diodes.within.the.IGBT.modules.Q13-Q18).and.to.provide.a.
means.of.disconnecting.the.filter.power.components.from.
the.power.mains..When.the.drive.is.turned.off,.both.contac-
tors.are.dropped.out.and.the.filter.phase.bank.assembly.is.
disconnected.from.the.mains.
When.the.drive.is.commanded.to.run,.the.precharge.resistors.
are.switched.into.the.circuit.via.contactor.2M.for.a.fixed.time.
period.of.five.(5).seconds..This.permits.the.filter.capacitors.
in.the.phase.bank.assembly.to.slowly.charge..After.the.five-
second. time. period,. the. supply. contactor. is. pulled. in. and.
the.precharge.contactor.is.dropped.out,.permitting.the.filter.
phase.bank.assembly.to.completely.charge.to.the.peak.of.the.
input.power.mains..Three.power.fuses.(11FU.-13FU).connect.
the.filter.power.components.to.the.power.mains..Very.fast.
semiconductor. power. fuses. are. utilized. to. ensure. that. the.
IGBT.modules.do.not.rupture.if.a.catastrophic.failure.occurs.
on.the.DC.link.of.the.filter.phase.bank.assembly.
The “Trap” Filter
. is. composed. of. a. series. of. capacitors.
(C84-C92),.inductors.(4L-6L).and.resistors.(16RES-18RES)..
The.“trap”.filter.acts.as.a.low.impedance.for.a.range.of.fre-
quencies.centered.at.the.PWM.switching.frequency.of.the.
filter.(20.khz)...The.purpose.of.the.trap.is.to.block.currents.
at. the. switching. frequency. of. the. filter. from. getting. onto.
the.power.mains.
The Three-Phase Inductor
. provides. some. impedance. for.
the. filter. to. “work. against”.. The. inductor. effectively. limits.
the.rate.of.change.of.current.at.the.input.to.the.filter.to.a.
reasonable.level.
The IGBT Phase Bank Assembly
. is. the. most. complicated.
power.component.in.the.harmonic.filter..The.purpose.of.the.
assembly.is.to.generate.harmonic.currents.required.by.the.
drive’s.AC.to.DC.converter.so.that.these.harmonic.currents.
are. not. drawn. from. the. power. mains.. The. phase. bank. is.
composed.of.a.series.of.IGBT.modules.(Q13-Q18).mounted.to.
a.liquid-cooled.heatsink,.a.filter.capacitor.“bank”.(C67-C76).
and.an.IEEE.519.Filter.Gate.Driver.board.(031-01786).which.
provides.the.On.and.Off.gating.pulses.to.the.IGBT’s.as.de-
termined.by.the.519.Filter.Logic.board..In.order.to.assure.an.
equal.sharing.of.the.voltage.between.the.series.connected.
capacitors.on.the.filter.bank,.“bleeder”.resistors.14RES.and.
15RES.are.connected.across.the.banks..In.order.to.counteract.
the.parasitic.inductances.in.the.mechanical.structure.of.the.
phase.bank,.the.filter.incorporates.“laminated.bus”.technology.
and.a.series.of.small.film.capacitors.(C77-C83)..The.technology.
used.is.identical.to.that.used.in.the.VSD’s.DC.to.AC.inverter.
section.of.the.drive..
Various.ancillary.sensors.and.circuit.boards.are.used.to.convey.
information.back.to.the.harmonic.filter.logic.board..The.fol-
lowing.list.describes.some.of.these.components.
•. A.thermistor.temperature.sensor,.RT5,.is.mounted.onto.the.
liquid-cooled.heatsink.to.provide.temperature.information.
•. Current. Transformers. 6T. and. 7T. sense. the. input. current.
drawn.by.the.VSD’s.AC.to.DC.converter.
•. DC. Current. Transformers. (DCCT1. and. DCCT2). sense. the.
current.generated.by.the.harmonic.filter.
•. The.Line.Voltage.Isolation.Board.(031-02022).senses.the.
input.voltage.to.the.system,.steps.the.voltage.down.to.a.
safe.level.and.provides.isolation.between.the.Filter.Logic.
board.and.the.power.mains.
•. The.Bus.Isolation.Board.(031-01624).incorporates.three.re-
sistors.to.provide.a.“safe”.impedance.between.the.DC.filter.
capacitors.located.on.the.phase.bank.assembly.and.the.filter.
logic.board..The.bus.isolation.board.provides.the.means.to.
sense.the.positive,.midpoint,.and.negative.connection.points.
of.the.filter’s.DC.link.