GE 869 - Page 205

CHAPTER 4: SETPOINTS SYSTEM
869 MOTOR PROTECTION SYSTEM – INSTRUCTION MANUAL 4–73
Figure 4-16: Motor Load Averaging Filter for VFD and Cyclic Load Motor Applications
89$1.cdr
Bypass Switch:
Setpoint
FUNCTION:
Setpoint
Off=0
AND
Enabled=1
IA IB IC
Phase Input Currents from CT Bank
Motor Load Filter Interval:
Setpoint
RUN
Motor Load Averaging Filter
RMS
FLEXANALOGS
Fltd RMS Curr A
Fltd RMS Curr B Fltd RMS Curr C
Fltd Mag Curr A
Fltd Mag Curr B Fltd Mag Curr C
Motor Load
()
RMSFLTDICRMSFLTDIBRMSFLTDIA
CurrentsRMSthreeofAverage
++
=
3
1
Fltd Motor Load
()
RMSICRMSIBRMSIA
CurrentsRMSthreeofAverage
++
=
3
1
Motor Load Filter Interval :
Setpoint
> 0
From “System Setup/VFD”
AND
RUN
÷ ÷ ø ö
ç ç è æ
cyclesinNx
F
cyclesx
n
F
Min
1
,16
1
Filter length
=
Filter length = Motor Load Filter Interval
AND
Real
Imag
VA VB VC
V & I
Phase Input Voltage from VT Bank