ABB ACS800 User Manual page 13


 
Q H

n
P

In the calculation sheets, calculations are at single points for Q = 20% to 100%
of nominal pump flow Qn. Q is the actual flow. H is the total dynamic head at
flow Q. The efficiency figures are multiplied with k-factors witch take into
account operating conditions with some accuracy. These correcting factors are
defined based on experience.
Efficiency

100 %
DRIVE
95 %
80 %
Graph 2. Typical efficiencies.
This gives the following formulas for power calculations:
Frequency converter control

Pvsdi

 

p


kmi Qi Qn
kvsdi 
table
Throttling control, assuming constant motor efficiency

 
Qi

Pthi



p

 
kpi Qi 2 4 .
ON/OFF control, assuming constant motor and pump efficiency

P
ON OFF _ avg

. 0 981
n
p
MOTOR
PUMP

  
Qi Hsi . 9 81

 
m kmi kvsdi * vsd

 
 
0 2 . 0 2 . Hst Hn

Hpi . 9 81
, where



kpi m
  
 
. 1 44 Qi Qn Qn

  
Qi Hn . 9 81
 
 

p m

vsd

m

p
Flow
, where

13