Introduction
It is recommended to set accurate motor parameters to a motor control inverter, since this will improve the control and stability of operation, and can increase the efficiency and reliability of the system. To determine the parameters, the EC-C1200 motor control inverter allows a user to perform an automatic motor parameter identification via the PowerUSER software.
Note that accurate motor parameters are also available directly from Danfoss Editron by creating a service ticket or contacting the service team via email: editron.service@danfoss.com. The parameters will be provided according to the motor serial number, which will negate the need to perform a separate identification run.
The motor parameter identification should not be confused with the resolver offset identification, which always has to be performed for any motor and inverter that will be run in closed-loop control using the resolver.
Before the identification
Some prerequisites have to be met before the identification can be performed:
1) The motor rating plate values have to be configured to the inverter parameters before the identification (see the motor control quick guide for more information about the rating plate values). The motor parameter identification can only determine the inductances, resistance, and other motor electrical properties if the basic values indicated in the rating plate are set correctly.
2) The DC-link of the inverter has to be supplied with the nominal voltage. The power supply has to be able to provide enough power so that the inverter can rotate the motor without issues.
3) Inverter limit settings have to be configured so that no limits are activating and limiting the inverter output during the identification run (e.g. speed, torque, power, etc. limits)
There are several different modes available for the identification, with the major categories being "standstill", "free rotating" and "fixed speed". If there is nothing connected to the motor shaft, standstill and rotating identification modes can be used. If the motor is already connected to other components, rotating mode is recommended, but note that the friction caused by external components can affect the accuracy of the parameter identification. If the motor is connected to an external motivator, e.g. a diesel engine, fixed speed identification mode can be used and will provide the most accurate results. A complete or partial identification can be performed, depending on which parameters should be measured.
How to run the identification
The inverter modulation has to be stopped (i.e. run command set to "false") before the identification can be performed. Identification mode can be selected with the signal 2.8.1.3 Parameter identification mode. The identification request can be given by setting the signal 2.8.1.1. Request parameter identification to "true". After this, the regular run command can be given to the inverter to start the identification, according to the active command configuration (see the application manual for more information about the command configurations).
The identification will run automatically and the signal 2.8.1.4 Parameter identification ready will indicate when the identification has been completed. During the identification, all estimated motor parameter values will be indicated in the corresponding signals in the signal groups 2.8.2 Identified PMSM parameters and 2.8.3 Identified current measurement offsets. It is recommended to observe the operation and status of the inverter during the identification run, e.g. via the PowerUSER signal scope to ensure there are no issues. If there are any disturbances during the ID run (for example, any limits are activated during the identification, the DC-link voltage drops too low or goes too high, or the inverter trips) the results will be unreliable and should not be taken into use. If this happens, reboot the inverter, change the limits, and/or check the power source and installation to ensure that the identification can be run without any limitations or disturbances, and perform the identification again.
After the identification is completed, the motor parameters can be saved permanently to the inverter's memory by setting the signal 2.8.1.2 Save identified parameters to "true". Note that the values cannot be saved to the memory as long as the run command is set to "true", thus the run command has to be switched off before the parameters are actually saved. The run command also has to be cycled before the inverter can be started again to run the motor normally. While saving the values, the inverter will automatically switch the parameter unit selection (2.3.1.8 Parameter units (SI/pu)) to "SI values". Before trying to run the motor, double-check the motor parameters manually and ensure that all necessary values have a reasonable value. If all of the SI values cannot be measured or their values seem unrealistic, switch the parameter units back to "Per units" before attempting to run the motor.
Troubleshooting
Issue | Notes | Recommended action |
Values given by the parameter identification are unrealistic and/or motor control is very poor with the identified values. | Compare the inductance values obtained by the transient measurements (Ltd and Ltq) with the values obtained by HF inductance measurement (Ld and Lq). If the corresponding values, e.g. Ld and Ltd, differ by more than 50% of the parameter value, the accuracy of the results could be compromised and the identification process should be performed again. | Try to perform the identification again, paying very close attention to any limits activating during the run or other issues affecting the accuracy of the identification. Any load changes on the motor during the identification can affect the results; ensure that no external forces are acting on the motor when running in free rotating or standstill ID modes. |
Inverter trips during the identification run. | The high-voltage DC power supply connected to the inverters DC-link must be able to absorb some generated power from the inverter. If this is not possible physically, it can cause an overvoltage trip while running the identification. | Check which trip occurred and change the parameters and/or system power supply to prevent the trip on the next run. Reboot the inverter before continuing. |
Inverter/motor is behaving erratically after the identification run, e.g. motor is not rotating at all. | If the inverter trips during the identification, the control system can get stuck in the identification phase and does not allow the user to run the inverter in a normal way before a reboot. | Reboot the inverter and try again. |
After a successful parameter identification and saving the obtained values, the inverter trips immediately after giving run command or does not rotate the motor at all. | After saving the identified parameters, the inverter will switch automatically to use the SI based parameter values. If, for example, the Rs measurement was skipped, the Rs value will be zero, and might cause the inverter control system to fail. | Check if the inverter is using SI or pu motor parameter units. After this, ensure that the used motor parameters values are not zero or unrealistically high. Enter correct values for the missing or incorrect parameters manually if necessary. |
Identification is not measuring/reporting values for some parameters. | Different parameters are measured in different modes, e.g. the back-EMF coefficient "Psi PM" cannot be measured in the standstill ID modes. Only parameters which each mode can measure will be shown in the identified parameters after the run. By default, the identification will skip measuring the resistance of the winding, because the measurement is very inaccurate. This can be changed through a parameter in the identification parameter group to allow Rs measurement. | Choose a different identification mode if necessary to measure all parameters. |