Danfoss VLT Series Design Manual page 20

2. Introduction to the VLT HVAC Drive
The laws of proportionality
This figure describes the dependence of flow, pressure and power consumption on rpm.
2
Q = Flow
Q
1
Q
2
H = Pressure
H
1
H
2
20
= Rated flow
= Reduced flow
= Rated pressure
= Reduced pressure
MG.11.B4.22 - VLT
P = Power
P = Rated power
1
P = Reduced power
2
n = Speed regulation
n = Rated speed
1
n = Reduced speed
2
Q n
1
F low
: =
Q n
2
H
1
Pressure
: =
H
2
(
P
1
Power
: =
P
2
® is a registered Danfoss trademark.
VLT ® HVAC Drive Design Guide
1
2
( )
n
2
1
n
2
)
n
3
1
n
2