vacon • 164
Parameters
Local contacts: https://www.danfoss.com/en/contact-us/contacts-list/
7.2.14
Protections
E
XTERNAL
F
AULT
An alarm message or a fault action and message is generated by an external fault external fault
signal in one of the programmable digital inputs (DI3 by default) using parameters P3.5.1.11 and
P3.5.1.12. The information can also be programmed into any of the relay outputs.
Z
ERO
S
PEED
C
OOLING
Defines the cooling factor at zero speed in relation to the point where the motor is running at nom-
inal speed without external cooling. See Figure 56.
The default value is set assuming that there is no external fan cooling the motor. If an external fan
is used this parameter can be set to 90% (or even higher).
If you change the parameter P3.1.1.4
, this parameter is automatically restored
to the default value.
Setting this parameter does not affect the maximum output current of the drive which is determined
by parameter P3.1.3.1 alone.
The corner frequency for the thermal protection is 70% of the motor nominal frequency (P3.1.1.2).
Figure 56. Motor thermal current I
T
curve
T
HERMAL
T
IME
C
ONST
This is the thermal time constant of the motor. The bigger the motor, the bigger the time constant.
The time constant is the time within which the calculated thermal stage has reached 63% of its final
value.
The motor thermal time is specific to the motor design and it varies between different motor man-
ufacturers. The default value of the parameter varies from size to size.
If the motor's t6-time (t6 is the time in seconds the motor can safely operate at six times the rated
current) is known (given by the motor manufacturer) the time constant parameter can be set basing
on it. As a rule of thumb, the motor thermal time constant in minutes equals to 2*t6. If the drive is
in stop stage the time constant is internally increased to three times the set parameter value. The
cooling in stop stage is based on convection and the time constant is increased. See Figure 58.
f
f
n
Par.
ID706=40%
0
9129.emf
I
T
100%
Overload area
P
cooling
Corner freq