Underload (Dry Pump) Protection - Honeywell HVAC400x Applications Manual

HVAC400X – APPLICATION MANUAL
NOTE: For a stall state to occur, the output frequency must be below this limit for a certain time.
10.9.3

Underload (Dry Pump) Protection

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 P3.9.16 (Underload Protection: Field Weakening
Area Load) and P3.9.17 (Underload Protection: 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 IL. If you use another current than the nominal motor current, the
precision of the calculation decreases.
NOTE: If you use long motor cables (max. 100 m) with small drives (≤ 1.5 kW (≤ 2.0 hp)), the motor current that
the drive measures can be much higher than the actual motor current. This is because there are
capacitive currents in the motor cable.
P3.9.15 UNDERLOAD FAULT (ID 713)
You can use this parameter to select the response of the drive to an 'Underload' fault.
If the underload protection function detects that there is not a sufficient load on the motor, an underload fault
occurs.
P3.9.16 UNDERLOAD PROTECTION: FIELD WEAKENING AREA LOAD (ID 714)
You can use this parameter to set the minimum torque that the motor needs when the output frequency of the drive
is higher than the frequency of the weakening point.
You can set the value of this parameter between 10.0 and 150.0% x TnMotor. This value is the limit for the
minimum torque when the output frequency is above the field weakening point.
If you change parameter P3.1.1.4 (Motor Nominal Current), this parameter goes automatically back to its default
value. See 5.9 Group 3.9: Protections.
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