Vacon 100 hvac Applications Manual

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Vacon 100 hvac Applications Manual Manual pdf 157 page image

NOTE!For a stall state to occur, the output frequency must be below this limit for acertain time.10.9.3 UNDERLOAD (DRY PUMP) PROTECTIONThe motor underload protection makes sure that there is a load on the motor when the driveoperates. If the motor loses the load, a problem can occur in the process. For example, a beltcan break or a pump become dry.You can adjust the motor underload protection with parameters P3.9.16 (UnderloadProtection: Field Weakening Area Load) and P3.9.17 (Underload Protection: Zero FrequencyLoad). The underload curve is a squared curve between the zero frequency and the fieldweakening point. The protection is not active below 5 Hz. The underload time counter doesnot operate below 5 Hz.The values of the underload protection parameters are set in percentage of the nominaltorque of the motor. To find the scaling ratio for the internal torque value, use the data in thename plate data of the motor, the motor nominal current and the nominal current of thedrive IL. If you use another current than the nominal motor current, the precision of thecalculation decreases.NOTE!If you use long motor cables (max. 100 m) with small drives (≤1.5 kW), the motorcurrent that the drive measures can be much higher than the actual motor current.It is because there are capacitive currents in the motor cable.P3.9.15 UNDERLOAD FAULT (ID 713)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)Use this parameter to set the minimum torque that the motor needs when the outputfrequency 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 thelimit 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 goesautomatically back to its default value. See Chapter 5.9 Group 3.9: Protections.PARAMETER DESCRIPTIONS VACON · 15724-HOUR SUPPORT +358 (0)201 212 575 · EMAIL: VACON@VACON.COM 10