
100.210-IOM (FEB 2015)
Page 54
VYPER
™
VARIABLE SPEED DRIVE
OPERATION
Figure.64.provides.the.VFD.and.Capacity.Control.setpoints.
typical.for.operation.
VFD
Maximum.Drive.Output
100%
Minimum.Drive.Output
20.%
Delay
Rate.of.Increase
%
Rate.of.Decrease
%
Capacity Control
The.Drive.Speed.will.increase.and.decrease.proportionally
with.the.Slide.Valve*.until.the.Slide.Valve*.reaches
98.%
and.the.Drive.Speed.reaches
75.%
Above.these.setpoints,.the.Drive.Speed.will.be.controlled
by.the.Rate.Of.Increase.and.Decrease.while.the.
Slide.Valve*.will.operate.independently.
*Slide.Valve.or.other.mechanical.unloader
Variable.Speed.Minimum.Slide.Valve.Position
40.0%
Figure 64 - Example 1 VFD and Capacity Control Setpoints
Example.1.(Figure.65).depicts.the.5.to.1.(5:1).control.strategy,.
which.is.characterized.by.rapid.response.to.highly.dynamic.
load.fluctuations..A.quick.start-up.from.zero.load.condition.is.
also.required..As.shown.in.Figure.64,.this.is.accomplished.by.
programming.total.speed.control.over.the.entire.operational.
speed.range..There.is.little.or.no.proportional.control.present.
for.this.setting..The.slide.valve.remains.loaded.throughout.
the. range. of. operation.. Capacity. is. totally. controlled. by.
motor.speed.
Often,.the.Vyper
™
.controlled.screw.compressor.is.used.as.
a.trim.compressor,.handling.the.fluctuating.portion.of.the.
load. while. used. in. combination. with. other. reciprocating.
compressors.for.the.base.load..This.allows.the.required.quick.
response.and.also.prevents.the.rapid.cycling.on.and.off.of.
the.other.compressors.in.the.system.
Some. additional. Vyper
™
. features. require. programming. in.
order.create.the.rapid.response.envelope.needed.for.5.to.1.
turndown.applications..The.Variable.Speed.Minimum.Slide.
Valve.Position.is.a.factory.default.and.is.related.to.the.Mini-
mum.Drive.Output.setting..however,.an.additional.control.
feature.is.needed.to.override.the.Variable.Speed.Minimum.
Slide.Valve.Position.setting.in.order.to.keep.the.Slide.Valve.
loaded.at.a.much.higher.level..Frick.recommends.that.the.
slide.valve.position.for.5:1.applications.be.set.as.high.as.97%...
The.required.setpoints.are.accessed.from.the.Compressor.
Safeties.Screen.
Figure 65 - 5:1 Turndown Suggested Control Strategy
Example 1 - Suggested Control Strategy for 5 to 1 (5:1) Turndown
Содержание Frick 572
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