GEA Grasso - Page 67

Grasso
Refri
g
eration Division
GRASSO SYSTEM CONTROL
01.2004/1 638660E_chapter2.doc Chap. 2 - 31
2.7.2.19 Low and high compressor motor speed alarm (for frequency control only)
Both low and high compressor motor speed are monitored. If the motor speed becomes too low or too high an
alarm is generated. The low compressor motor speed alarm does not become active until the start up process
has been completed.
The low compressor motor speed alarm function is illustrated in the following diagram.
N
mot
Compressor motor speed
A.. Time characteristic of the
compressor motor speed
W.. Warning limit
Al.. Alarm limit
U.. Unloaded start up
ML W.. Warning active
ML A.. Alarm active
3.. Reset of the active alarm
Figure 2.36, Low compressor motor speed alarm
Motor speed 
Nmot low alarm 
Low warning + 
Motor speed: Actual compressor motor speed in rpm
Nmot low alarm: Alarm limit for low compressor motor speed in rpm
Low warning: Enter the warning value as an offset to the alarm limit in
<< Limit values 01 >> rpm
The high compressor motor speed alarm function is illustrated in the following diagram.
N
mot
Compressor motor speed
A.. Time characteristic of the
compressor motor speed
W.. Warning limit
Al.. Alarm limit
ML W.. Warning active
ML A.. Alarm active
3.. Reset of the active alarm
Figure 2.37, High compressor motor speed alarm
Motor speed 
Nmot hi alarm 
High warning - 
Motor speed: Actual compressor motor speed in rpm
Nmot hi alarm: Alarm limit for high compressor motor speed in rpm
High warning: Enter the warning value as an offset to the alarm limit in
<< Limit values 01 >> rpm