Motor Stall Protection - Honeywell HVAC400x Applications Manual

HVAC400X – APPLICATION MANUAL
The bigger the motor, the longer the time constant.
In different motors, the motor thermal time constant is different. It also changes between different motor
manufacturers. The default value of the parameter changes from dimension to dimension.
The t6-time is the time in seconds that the motor can safely operate at six times the rated current. It is possible that
the motor manufacturer gives the data with the motor. If you know the t6 of the motor, you can set the time constant
parameter with its help. Usually, the motor thermal time constant in minutes is 2*t6. When the drive is in the STOP
state, the time constant is internally increased to three times the set parameter value because the cooling operates
based on convection. See Fig. 29. Calculation of the motor temperature.
P3.9.10 MOTOR THERMAL LOADABILITY (ID 708)
You can use this parameter to set the thermal loadability of the motor.
For example, if you set the value to 130%, the motor goes to the nominal temperature with 130% of the motor
nominal current.
I/I
T
T
105%
A. Current.
B. Fault / Alarm.
C. Trip area.
10.9.2

Motor Stall Protection

The motor stall protection function gives protection to the motor against short overloads. An overload can be
caused, e.g., by a stalled shaft. It is possible to set the reaction time of the stall protection shorter than that of the
motor thermal protection.
The stall status of the motor is specified with parameters P3.9.12 Stall Current and P3.9.14 Stall Frequency Limit. If
the current is higher than the limit, and the output frequency is lower than the limit, the motor is in a stall status.
The stall protection is a type of overcurrent protection.
EN2B-0417GE51 R0719
A
D
E
Fig. 29. Calculation of the motor temperature
Legend
B
F
D. Loadability 80%.
E. Loadability 100%.
F. Loadability 130%.
128
t
C
t