Motor de Induccion ETAP

Chapter 26

Parameter Estimation

The ETAP Parameter Estimation Module calculates equivalent circuit model parameters for induction machines and synchronous motors at starting condition. This calculation is based on an advanced mathematical estimation and curve fitting technique, which requires only the machine performance characteristic data. This data is readily available from machine manufactures or can be obtained from field tests. The estimated model parameters include the resistance and reactance representing the machine stator, rotor and magnetizing branches characteristics. The estimated model, together with its parameters, can be used to represent the machine dynamics during motor starting and Transient Stability Studies. This chapter describes the interfaces, input and output data involved in running the Parameter Estimation Program. All other related operations including data update, plot and print will also be explained. An overview of the calculation algorithm is provided for your reference. This chapter is organized into five sections. The Start Parameter Estimation section describes how to start the parameter estimation calculation. The Parameter Estimation Editor section explains each input data and the calculated data for and from the calculation, as well as additional output information. The Motor Parameter Update Editor section details the updateable data provided to the Machine Editor when using the estimated model and its parameters. The Calculation Method provides some technical background on the algorithm used for the estimation calculation. And finally, the Output Reports section provides a detailed description of the available Output Reports, their various formats and how to view and print them.

Operation Technology, Inc. 26-1 ETAP 7.5.2 User Guide

Parameter Estimation Start Parameter Estimation

26.1 Start Parameter Estimation To launch a Parameter Estimation, click on the Parameter Estimation Start button located in the Model page of the Induction Machine Editor.

Click this button to open the Parameter Estimation Editor.


Parameter Estimation Parameter Estimation Editor

26.2 Parameter Estimation Editor The Parameter Estimation Editor consists of a Parameters page and a Curve page.

26.2.1 Parameters Page This page provides entry fields for all input data necessary to run a parameter estimation calculation. Estimated parameters and other output data is also displayed on this page.

Requirement In this area, there are three sets of data: input, calculated and deviation. The input fields are user-defined, while the remaining fields are calculated by ETAP.

Input The Input section contains machine performance characteristic data, which is available from the machine manufacturer, machine nameplate, or derived from field tests. This data must be provided in order to run a parameter estimation calculation. The first time this page is opened, the input data fields will be automatically filled using data contained in the Machine Editor Nameplate and Model pages. However, you can modify any of this automatically input data independently of the Machine Editor.



Calculated If the calculation converges, the machine performance characteristic data using the estimated model parameters will be displayed here. This data is provided for comparison purposes.

Deviation The deviation fields show the percent deviation between the input data and the calculated data.

Locked Rotor I The machine locked-rotor current (at motor rated kV). The input and calculated data are a percentage of the rated full load current of the machine, and the deviation is also a percentage.

Locked Rotor PF The machine locked-rotor power factor in percent.

Locked Rotor T The machine locked-rotor torque. The input and calculated data is in percent of the machine rated power and synchronous speed. The deviation is in percent.

Tmax The machine maximum torque. The input and calculated data are in percent of the machine rated power and synchronous speed. The deviation is in percent.

Full Load Slip The machine full load slip, in percent.

Full Load PF The machine full load power factor, in percent.

Full Load Eff The machine full load efficiency, in percent.

Refresh Button Every time the Parameters page of the Parameter Estimation Editor is opened, the input data will be compared with the Machine Editor data. If any difference exists, this button will be enabled; otherwise it is disabled (grayed out). Press this button to re-compare all input data with the Machine Editor data.

Solution Parameters This section defines and displays the solution parameters of the calculation.

Max Deviation Displays the maximum allowed value among all deviations in the Requirement section. The value is a percentage.

Precision Enter the value for the solution precision (in percent) that is used to check for calculation convergence. The calculation stops when all deviations are less than, or equal to this value. The recommended value for this setting is between 1.0 and 5.0 percent. The default is 2 percent.



Acceleration Factor Enter the convergence acceleration factor to be used between iterations. Typical values are between 0.1 and 0.5. The default value is 0.25.

Estimated Parameters This section displays the estimated (calculated) machine equivalent circuit model parameters.

Xs Displays the machine stator reactance in percent on the machine base.

Rs Displays the machine stator resistance in percent on the machine base.

Xm Displays the machine magnetizing branch reactance in percent on the machine base.

Xr lr Displays the machine rotor reactance at the locked-rotor condition in percent on the machine base.

Xr fl Displays the machine rotor reactance at the full load condition in percent on the machine base.

Rr lr Displays the machine rotor resistance at the locked-rotor condition in percent on the machine base.

Rr fl Displays the machine rotor resistance at the full load condition in percent on the machine base.

Estimate Button Press this button to run the parameter estimation calculation.

Update Button When a calculation is completed successfully, the Update button will be enabled. Click this button to open the Motor Parameter Update Editor whose functions will be described separately in its own section.

Parameter Estimation Report Selection List This list contains all the output files from the parameter estimation calculations in the current project folder. Select a file to view the report or to run a new calculation. Note: In the latter case, the existing file will be over written. When Prompt is selected, a new file will be created.




Parameter Estimation Report Manager Button The Parameter Estimation Report Manager button is used to access the various Output Reports. The functions of the Parameter Estimation Report Manager will be described separately in its own section.

Help This opens the Help file topic for the Parameter Estimation section.

Close This closes the Parameter Estimation Editor and saves all data.

Cancel This closes the Parameter Estimation Editor without saving any modified data.


26.2.2 Curves Page This page displays the machine equivalent circuit model, its parameters, and the characteristic curves generated from the model.

Update Button When a calculation is completed successfully, the Update button will be enabled. Click this button to open the Motor Parameter Update Editor, whose functions will be described separately in its own section.

Parameter Estimation Report Selection List This list contains all the output files from the parameter estimation calculations that are included in the current project folder. Select a file to view the report or to run a new calculation. Note: In the latter case, the existing file will be over written. When Prompt is selected, a new file will be created.

Parameter Estimation Report Manager Button




The Parameter Estimation Report Manager button is used to access the various Output Reports. Functions of the Parameter Estimation Report Manager will be described separately in its own section.

Help This opens the Help file topic for the Parameter Estimation section.

Cancel This closes the Parameter Estimation Editor without saving any modified data.

Parameter Estimation Parameter Estimation Update Editor

26.3 Motor Parameter Update Editor This editor provides options that allow you to update machine data that were based on the calculated equivalent circuit model.

Model Data The data in the lower portion (non-boxed area) is from the machine Model page under the Model section. This data is compared with the calculated data (boxed area) from the estimated model.

Rs The machine stator resistance in percent on the machine base.

Xs The machine stator reactance in percent on the machine base.

Xm The machine magnetizing branch reactance in percent on the machine base.

Xr lr The machine rotor reactance at the locked-rotor condition in percent on the machine base.

Xr fl The machine rotor reactance at the full load condition in percent on the machine base.



Rr lr The machine rotor resistance at the locked-rotor condition in percent on the machine base.

Rr fl The machine rotor resistance at the full load condition in percent on the machine base.

Nameplate Data The Existing data is from the machine Nameplate page under the Ratings section, which is compared with the calculated data list from the estimated model (located above the Existing data).

kVA The machine rated kVA.

FLA The machine rated full load current in amperes.

PF The machine rated power factor at 100% loading in percent.

Eff The machine rated efficiency at 100% loading in percent.

H The machine total inertia in MW-Sec/MVA.

Torque The machine rated torque in ft-lb in English unit system or in N-m in Metric unit system.

Update Checkbox Check this box if you wish to update the Nameplate Data.

Loading Data The Existing data is derived from the machine Nameplate page under the Ratings section, which is compared with the calculated data list above from the estimated model (located above the Existing data).

PF 50% The machine rated power factor at 50% loading in percent.

PF 75% The machine rated power factor at 75% loading in percent.

Eff 50% The machine rated efficiency at 50% loading in percent.

Eff 75% The machine rated efficiency at 75% loading in percent.



Update Checkbox Check this box if you wish to update the Loading Data.

Short-Circuit Data The Existing data is from the machine Model page under the Locked Rotor section, ANSI Short-Circuit Z section, and Parameters section respectively. This data is compared with the calculated data list above the estimated model (located above the Existing data).

LRC The machine locked-rotor current (at motor rated kV) in percent of the rated full load current of the machine.

PFlr The machine locked-rotor power factor in percent.

½ cy X The machine short-circuit impedance in percent on machine base; used for ANSI ½ cycle fault calculation.

1.5-4 cy X The machine short-circuit impedance in percent on machine base; used for ANSI 1.5-4 cycle fault calculation.

X/R The machine X/R ratio (Xsc/Ra).

Td' The machine transient time constant in seconds.

Update Checkbox Check this box if you wish to update the Short-Circuit Data.

Characteristic Data The Existing data is generated from the machine Nameplate page under the Ratings section and Model page under the Torque section, respectively. This data is compared with the calculated data list above the estimated model (located above the Existing data).

LRT The machine locked-rotor torque in percent.

MaxT The machine maximum torque in percent.

FLT The machine full load torque in percent.

S@MaxT The machine slip at the maximum torque in percent.




Sr The machine rated slip in percent.

Update Checkbox Check this box if you wish to update the Characteristic Data.

Help Button This opens the Help file topic for the Parameter Estimation section.

Update Button This updates the data in any of the sections that have their Update boxes checked.

Cancel Button This closes the Motor Parameter Update Editor without updating any data.

Parameter Estimation Calculation Method

26.4 Calculation Method

Reference Paper The machine equivalent circuit model parameter estimation calculation method uses an algorithm based on limited available data, which is described in the following reference paper:

Sonchai Ansuj, Farrokh Shokooh, and Roland Schinzinger, “Parameter Estimation for Induction Machines Based on Sensitivity Analysis”, IEEE Transactions on Industry Applications, Vol. IAS 25 pp. 1035-1040, Nov./Dec. 1989.

Equivalent Circuit Model This algorithm estimates the parameters in the following equivalent induction machine circuit model.

Parameters for this model are:

• Rs Stator resistance • Xs Stator reactance • Xm Magnetizing reactance • Rr lr Rotor resistance at locked-rotor • Rr fl Rotor resistance at full load • Xr lr Rotor reactance at locked-rotor • Xr fl Rotor reactance at full load

This data is indicated in the machine steady-state performance curve below:


Parameter Estimation Calculation Method


The algorithm starts with a simplified equivalent circuit that omits the magnetizing branch. Using this simplified model, the model parameters are evaluated first. These parameters are then used to arrive at the more accurate values using the detailed equivalent circuit model. At this stage, a sensitivity analysis is applied using an iterative process that continuously adjusts the estimated parameters until the percent deviations fall within a specified tolerance between the calculated values for the input parameters and the actual input. Both rotor parameters Rr and Xr are functions of slip and their respective cage factors. Therefore, two sets of Rr and Xr are estimated, with Rr lr and Xr lr representing the values at the locked-rotor condition, and Rr fl and Xr fl representing the values at the full load condition. The induction machine equivalent circuit described above can actually represent any type of rotor design. Single-cage, double-cage, and even wound-rotor types are accurately accounted for by the two sets for Rr and Xr. The program requires that the machine nameplate data, along with two specific points from the machine performance curves, are available. These points, which include the locked-rotor torque, locked-rotor current, locked-rotor power factor and breakdown torque, may be obtained from actual machine tests or from curves supplied by the manufacturer. Indeed, these points are often the only reliable information available from the performance curves, since the rest of the curve might have been provided merely as an indication of the machine’s generic behavior.

Parameter Estimation Required Data

26.5 Required Data The input data for the algorithm is the machine performance characteristic data, grouped according to the three loading conditions usually specified for the machine, described as follows: Locked-Rotor • Ilr Locked-rotor current • PFlr Locked-rotor power factor • Tlr Locked-rotor torque Full Load • Sr Rated full load slip • PFfl Full load power factor • Eff fl Full load efficiency

Maximum Torque • Tmax Maximum torque


Parameter Estimation Output Reports

26.6 Output Reports If the current calculation succeeds or a valid output file name is selected from the Parameter Estimation Report Selection List, the Output Reports can be accessed by pressing the Parameter Estimation Report Manager button. The Parameter Estimation Report Manager button is located next to the Parameter Estimation Report Selection List as shown in the figure below.

26.6.1 Parameter Estimation Report Manager Click the Parameter Estimation Report Manager button to open the Parameter Estimation Report Manager. The Parameter Estimation Report Manager offers various report formats and consists of four pages.

Complete Page Use this page to select the Complete Output Report.

You can view the file using the Viewer, or create a file that can be printed or emailed (PDF, MS Word, Rich Text Format, MS Excel). Your selection can also be assigned as the default report format if you check the Set As Default box. These selection buttons are offered on all four pages of the Report Manager.



The first page of the Complete Report provides input data, estimated model parameters and a comparison between the input data and similar data generated by the estimated model.

The second page of the Complete Report tabulates the machine characteristics for all key quantities as a function of machine slip. These quantities include machine speed, torque, current, power factor, and efficiency. It also reports the machine power factor and the efficiency at different loading conditions.



Input Page This page allows you to select the Input Data Report.

The Input Report displays the input data, and is equivalent to the input data section in the Complete Report.

Result Page This page allows you to select different data formats for your calculation results.




The Estimated Parameters Report is equivalent to the Estimated Parameters and Input & Results sections in the Complete Report. The Loading Characteristics Report is the same as the loading section of the second page of the Complete Report. The Motor Characteristics Report is equivalent to the tabulation portion of the second page of the Complete Report.

Summary Page This page provides the data format for calculation summary.

The Summary Report is equivalent to the Input & Results sections in the Complete Report.

Motor de Induccion ETAP

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