The motor thermal protection can be adjusted with parameters. The thermal current IT
specifies the load current above which the motor is overloaded. This current limit is a
function of the output frequency.
The thermal stage of the motor can be monitored on the control keypad display. See the
product's User Manual.
NOTE!
If you use long motor cables (max. 100 m) with small drives (≤1.5 kW), the motor
current that the drive measures can be much higher than the actual motor current.
It is because there are capacitive currents in the motor cable.
CAUTION!
Make sure that the airflow to the motor is not blocked. If the airflow is blocked, the
function does not protect the motor, and the motor can become too hot. This can
cause damage to the motor.
8.5
PARAMETERS OF STALL PROTECTION (IDS 709 TO 712)
The motor stall protection function gives protection to the motor against short overloads. An
overload can be caused, for example, 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 ID710 (Stall current) and ID712
(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.
NOTE!
If you use long motor cables (max. 100 m) with small drives (≤1.5 kW), the motor
current that the drive measures can be much higher than the actual motor current.
It is because there are capacitive currents in the motor cable.
8.6
PARAMETERS OF UNDERLOAD PROTECTION (IDS 713 TO 716)
The motor underload protection makes sure that there is a load on the motor when the drive
operates. If the motor loses the load, a problem can occur in the process. For example, a belt
can break or a pump become dry.
You can adjust the motor underload protection with parameters ID714 (Field Weakening Area
Load) and ID715 (Zero Frequency Load). The underload curve is a squared curve between the
zero frequency and the field weakening point. The protection is not active below 5 Hz. The
underload time counter does not operate below 5 Hz.
The values of the underload protection parameters are set in percentage of the nominal
torque of the motor. To find the scaling ratio for the internal torque value, use the data in the
name plate data of the motor, the motor nominal current and the nominal current of the
drive IH. If you use another current than the nominal motor current, the precision of the
calculation decreases.
VACON · 370
PARAMETER DESCRIPTIONS
8
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