4.17. Defining parameters of the Induction Motor
EA-PSM has a functionality to calculate static and dynamic induction motor starting. In this section, information will be provided on how to define induction motor parameters.
Double click on the motor element and “General” properties tab ( Figure 3.34 ) will open. Active and reactive power of the induction motor can be defined manually by entering “Real power, P” and “Reactive power, Q” or “Power factor, cos φ ” values.
Note : “Real power, P” is the electrical power that can be measured with a power analyzer and it is not a mechanical power that is usually provided on the nameplate of the induction motor.
For static induction motor starting calculation, data in the “Configure” tab should be specified.:
Electrical power of the induction motor will depend on the mechanical load. With EA-PSM it is possible to calculate the electrical power of the induction motor without performing measurements, however, load properties and induction motor specifications need to be defined. For this purpose, in the induction motor properties window select “Dynamics” tab and push the check box next to the inscription “Use dynamics” as shown:
When this box is selected, data described in “General” and “Configure” tabs will not be used for the calculations. Real and reactive power as well as starting current will be automatically calculated according to the induction motor specifications in “Dynamics” tab and load properties in “Load properties” tab.
It will be also possible to calculate dynamic motor starting after this data is specified.
Data to be specified in “Dynamics” and “Load properties” tabs:
RPM – rated revolutions per minute,
J – rotor mechanical inertia,
Xls – stator leakage reactance per phase,
Xlr – rotor leakage reactance per phase,
Xm – magnetizing reactance per phase,
Rs – stator resistance per phase,
Pm – rated mechanical power,
B – friction coefficient,
Efficiency – induction motor efficiency,
Tm_n – full load torque,
Load type: “Constant” – typical for screw compressors and conveyors; “Linear; “Square” – typical for centrifugal pumps and fans; “Cube”; “Polynomial”.
Load – load side mechanical load momentum for the induction motor axis.
Load
– load side rated load speed at which defined momentum will appear.
Load J – load side load mechanical inertia.
Gear ration – allows to specify load speed in respect to motor speed.
Most of this data can be given by the induction motor manufacturer. However, if it is not provided, it is highly recommended to use motor models that are provided in EA-PSM library (push drop down menu button that is in the tab "General").
EA-PSM allows to evaluate motor capacitance influence on short circuit currents and other calculations. User can specify this value manually or use recommended value as depicted:
