
100.210-IOM (FEB 2015)
Page 56
VYPER
™
VARIABLE SPEED DRIVE
OPERATION
VFD
Maximum.Drive.Output
100%
Minimum.Drive.Output
50.%
Delay
Rate.of.Increase
3.%
5.SEC
Rate.of.Decrease
3.%
5.SEC
Capacity Control
The.Drive.Speed.will.increase.and.decrease.proportionally
with.the.Slide.Valve*.until.the.Slide.Valve*.reaches
95.%
and.the.Drive.Speed.reaches
50.%
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
25.0%
NOTE: Slide Valve Range limited to protect compressor
Figure 69 - Example 2 VFD and Capacity Control Setpoints
NOTICE
The Variable Speed Minimum Slide Valve Position of
25% is a factory default value based on the minimum
slide valve position at 50% speed.
Figure 68 - 2:1 Turndown Suggested Control Strategy
The.standard.2:1.Turndown.Control.Strategy.is.depicted.in.
Figure.68..This.control.strategy.is.a.variation.on.the.generic.
control. strategy. described. previously.. Not. all. applications.
require.or.are.suitable.for.the.very.low.speeds.obtainable.
by.the.Vyper
™
.drive..Many.times.the.motor.is.the.limiting.
factor.and.is.not.suitable.for.20%.speed.but.is.capable.of.
50%.speed..For.these.applications,.the.settings.within.the.
Quantum
™
LX.can.assure.that.the.motor.never.runs.slower.
than.the.allowable.minimum.speed.
Figure.69.provides.the.VFD.and.Capacity.Control.setpoints.
typical.for.the.operation.shown.in.Figure.68.
VFD Proportional Band –
This.is.the.value.above.the.Capac-
ity.Control.setpoint.for.forward.action.at.which.the.output.to.
the.drive.will.match.the.maximum.output.setpoint..Typically,.
proportional. control. alone. will. not. permit. running. at. the.
control.setpoint..If.the.pressure.is.within.the.proportional.
band. but. not. increasing. the. output. will. no. increase. with.
proportional.control.only.
VFD Integration Time –
.This.is.the.value.that.sets.the.in-
crease.of.the.proportional.component.over.time.
Example:.with.the.following.setpoints,.Actual.Value.=.21psig
Capacity.Control. [20psig]
Maximum.Output.[100%]
Minimum.Output. [20%]
VFD.Proportional.Band.
[4psig]
VFD.Integration.Time.
[30.sec]
Example 2 - Suggested Control Strategy for Standard 2 to 1 (2:1) Turndown
Содержание Frick 572
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