Danfoss VLT AutomationDrive Design Manual page 51

Introduction to FC 300
3 3
Illustration 3.15 Figure ETR: The X-axis shows the ratio between
I and I
motor motor
before the ETR cut of and trips the drive. The curves show the
characteristic nominal speed, at twice the nominal speed and at
0,2 x the nominal speed.
At lower speed the ETR cuts of at lower heat due to less cooling
of the motor. In that way the motor are protected from being
over heated even at low speed. The ETR feature is calculating
the motor temperature based on actual current and speed. The
calculated temperature is visible as a read out parameter in
16-18 Motor Thermal in the FC 300.
50
t [s]
2000
1000
600
500
400
300
200
f OUT = 1 x f M,N (par. 1-23)
100
60 f OUT = 2 x f M,N
50
f OUT = 0. 2 x f M,N
40
30
20
I
M
10
I (par. 1-24)
1.0 1.2 1.4 1.6 1.8 2.0
M,N
nominal. The Y- axis shows the time in seconds
MG.33.BD.02 - VLT
FC 300 Design Guide
®
is a registered Danfoss trademark