VLT ® 2900 Series - Via a PTC thermistor that is mounted on the motor. The thermistor is connected between terminal 50 (+10V) and one of the digital input terminals 18, 19, 27 or 29. See parameter 300 Digital inputs. 0.0 - 10.0 Hz 0.0 Hz - Thermal load calculation (ETR - Electronic Thermal Relay), based on present load and time. This is compared with the rated motor current I M,N and rated motor frequency f M,N . The calculations take into account the need for lower loading at low speeds due to the motor's internal ventilation being reduced. The start frequency is active for the time set in param- eter 120 Start delay , after a start command.
The output frequency will 'jump' to the next preset frequency. Cer- tain motors, such as conical anchor motors, need an extra voltage/start frequency (boost) at start to disen- gage the mechanical brake. To achieve this parame- ters 130 Start frequency and 131 Initial voltage are used. Set the required start frequency. It is a precondition that parameter 121 Start function , is set to Start fre- quency/voltage clockwise [3] or Start frequency voltage in reference direction [4] and that in parameter 120 Start delay a time is set and a reference signal is present. NB! If parameter 123 is set higher than param- eter 130, the start delay function (param- eter 120 and 121) will be skipped.
Programming ETR functions 1-4 do not begin to calculate the load until you switch to the Setup in which they have been selected. This means that you can use the ETR func- tion even when changing between two or more motors. Select No protection [0] if you do not want a warning or trip when a motor is overloaded. Select Thermistor warning [1] if you want a warning when the connected thermistor becomes too hot. Select Thermistor trip [2] if you want a trip when the connected thermistor becomes too hot. Select ETR warning 1-4 if you want a warning when the motor is overloaded according to the calculations.
You can also programme the frequency converter to give a warning signal via one of the digital outputs. Select ETR Trip 1-4 if you want a trip when the motor is over- loaded according to the calculations. 0.0 - 200.0 V 0.0 V Initial voltage is active for the time set in parameter 120 Start delay , after a start command. This parameter can be used for example for lifting/dropping applications (conical anchor motors). Set the required voltage necessary to cut out the me- chanical brake.
It is assumed that parameter 121 Start function , is set to Start frequency/voltage clockwise [3] or Start frequency/voltage in reference direction [4] and that in parameter 120 Start delay a time is set, and that a reference signal is present. NB! This function cannot protect the individual motors in the case of motors linked in par- allel. = factory setting, () = display text, [] = value for use in communication via serial communication port MG.29.A3.02 - VLT ® is a registered Danfoss trademark 25 130 Start frequency (Start frequency) Value: Function: Description of choice: 131 Initial voltage (INITIAL VOLTAGE) Value: Description of choice: Function: Description of choice: