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2.2.10
Group Protections: Menu PAR G10
Parameters of Motor thermal protection (P10.9 to P10.12 and P10.18-P10.19)
The motor thermal protection is to protect the motor from overheating. The drive is capable of
supplying higher than nominal current to the motor. If the load requires this high current there
is a risk that the motor will be thermally overloaded. This is the case especially at low frequen-
cies. At low frequencies the cooling effect of the motor is reduced as well as its capacity. If the
motor is equipped with an external fan the load reduction at low speeds is small.
The motor thermal protection is based on a calculated model and it uses the output current of
the drive to determine the load on the motor.
The motor thermal protection can be adjusted with parameters. The thermal current I
fies 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 chapter 1.
If you use long motor cables (max. 100m) together with small drives (1.5 kW) the
motor current measured by the drive can be much higher than the actual motor
current due to capacitive currents in the motor cable. Consider this when setting up
the motor thermal protection functions.
The calculated model does not protect the motor if the airflow to the motor is
reduced by blocked air intake grill. The model starts from zero if the control board is
powered off.
Parameters of Stall protection (P10.2 to P10.4)
The motor stall protection protects the motor from short time overload situations such as one
caused by a stalled shaft. The reaction time of the stall protection can be set shorter than that
of motor thermal protection. The stall state is defined with two parameters, P10.3 (
Stall frequency limit
and P10.4 (
current limiter has reduced the output frequency below the P10.4 for the time P10.3 than the
set limit the stall state is true. There is actually no real indication of the shaft rotation. Stall
protection is a type of overcurrent protection.
If you use long motor cables (max. 100m) together with small drives (1.5 kW) the
motor current measured by the drive can be much higher than the actual motor
current due to capacitive currents in the motor cable. Consider this when setting up
the motor thermal protection functions.
Parameters of Underload protection (P10.5 to P10.8)
The purpose of the motor underload protection is to ensure that there is load on the motor
when the drive is running. If the motor loses its load there might be a problem in the process,
e.g. a broken belt or a dry pump.
Motor underload protection can be adjusted by setting the underload curve with parameters
P10.6 (Underload protection: Field weakening area load) and P10.7 (
Zero frequency load
frequency and the field weakening point. The protection is not active below 5Hz (the underload
time counter is stopped).
2
). If the current is as high as the P1.6 (Current Limit) and the
), see below. The underload curve is a squared curve set between the zero
Description of Groups
speci-
T
Stall time
Underload protection:
)
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