3.3.9 Using The Measure Button
While working through the Quick Start Tutorial (section 3, chapter 2), you may have noticed that the dialogue box for the test R - Winding Resistance - contained a button labeled ‘Measure’.
In fact, most tests have a Measure button within the dialogue box. It is included there to allow you to fill in various fields in the dialogue box by using the AT3600 to measure the value from a sample transformer.
All tests with a Measure button will allow you to enter a value into the test limits section of the dialogue box.
In addition, some tests can also make use of the Measure button to select the test conditions. The programming details for each test in section 4 (Programming Tests) later in this chapter, specify which tests allow the Measure button to enter the test parameter values.
HARDWARE CONNECTIONS FOR USING THE MEASURE BUTTON
Before attempting to use the Measure button:
- Make sure you have connected your tester's Auxiliary Port (on the rear panel) to a suitable Comm Port on your PC. (This may be Comm Port 2 if your mouse is already using Comm Port 1.)
- Set up the Comm Port on the PC.
From the Top Level menu,
In the dialogue box, select the PC communications port which is connected to the transformer tester.
WARNING: If the chosen ‘COM’ port is reserved by another Windows application, an error message will appear. You should select another port.
- Fit the appropriate fixture to the tester.
- Have available both a sample transformer, and possibly a shorting header if you wish to add tests to the program for which you will be applying short-circuit compensation.
EXAMPLE OF USING THE MEASURE BUTTON WITH THE LS TEST
LS - Winding Inductance (Series Circuit) - is one of the tests where both the test voltage and frequency, and the actual measurement may be obtained by using the Measure button. The following example assumes that this is what you wish to do.
Initially select the LS test in the normal way by double-clicking with the mouse in the Available Tests list.
In the LS test dialogue box:
Enter the terminal names in the normal way.
Select the integration you require if different from the default setting of Medium. In the Test Parameters section, leave both the Signal and the Frequency edit boxes blank.
The default units button for the Signal is ‘mV’. With this setting, the Editor will enter the test voltage chosen by the tester, changing as appropriate to the ‘V’ button if the signal is large. Alternatively, if you wish the test signal to be determined as a current, click on the ‘mA’ units button.
Finally, in the lower section of the dialogue box, select the desired limits type.
At this point, the dialogue box should be as follows:
Now, using the mouse, click on the Measure button.
Because the LS test is one where short-circuit fixture compensation could be applied, you will then see the following message:
If the value of inductance is high, then compensation may not be needed, and you may click on ‘OK’ with ‘Measure without Fixture Compensation’ selected.
If you click on ‘OK’ with ‘Compensate Fixture’ selected, then there will be an additional message, which in general depends on whether the test requires short- or open-circuit compensation. In this case, the LS test requires short-circuit compensation, so the following dialogue box will be shown:
Fit the required short-circuit header, and click on ‘OK’.
The Editor will now command the tester to perform the Fixture Compensation for the required test (in this case LS). The tester will then store the ‘zero’ value, and subtract it from the next result returned for the test.
If the short-circuit links are not correctly fitted, you may see an error message which allows you to try again, or to cancel the compensation.
Assuming no errors, when the tester has finished the compensation measurement, you will be prompted to remove the shorting links, and fit the sample transformer:
After you have clicked on the ‘OK’ button, the tester will be commanded to make its measurements, and you will see the following message:
When the measurements have finished, the display will return to the dialogue box for the LS test, with values entered for the test signal, the frequency and the nominal inductance:
From this point, it is very easy for you to complete the dialogue box by simply entering the values you require for the Negative and Positive percentage limits.
If you have chosen fixed voltage, current or frequency conditions it may not be possible for the tester to make a measurement. For example, if the AC impedance of the winding under test is only 0.1Ω at the specified frequency and you have specified a 5V test signal, then the AT would have to supply 5V / 0.1Ω = 50 Amps!
You will then see a warning similar to this:
Check first that the winding is properly connected to the right nodes.
Choose ‘Yes’ and the AT will choose suitable voltage conditions for you and enter them into the test dialogue. Choose ‘No’ and no conditions will be chosen. See Chapter 7 – Tests and test conditions for suitable values.
RESTRICTIONS FOR AUTOMATICALLY OBTAINING THE TEST PARAMETERS
As shown above, the LS - Winding Inductance (Series Circuit) - test is one where both the test voltage (or current) and frequency may be obtained automatically by using the Measure button.
Alternatively, you may wish to specify yourself either one or both of the parameters before using the Measure button. In this case, the tester will attempt to make use of the parameter(s) that you have specified, and enter a value only for parameters that you have not specified.
In general, all tests have restrictions on which test parameters may be (or have to be) specified, and which may be chosen automatically. In the case of the LS - Winding Inductance (Series Circuit) - test, the valid combinations are summarized in the following table:
(The combination that is not allowed, is to specify the voltage (or current), and ask the AT to find the frequency.)
If you have entered a non-permitted combination, the Editor will display a warning message when you click on the Measure button, and there will be no measurement until you correct the error.
WHAT HAPPENS WITH DIFFERENT TYPES OF LIMIT?
In the example shown above, percentage limits were chosen before clicking on the Measure button. In this case, the measured result from the tester is inserted as the nominal value, allowing you to set the limits for the test as a percentage either side of this nominal value.
If you choose one of the other possible limit types before clicking on the Measure button, the following table shows the way in which the measured result will be converted to edit box values:
|nom ← result
|neg%| ← no change
pos% ← no change
|nom dB ← result
|neg dB| ← no change
pos dB ← no change
|min ← result - 0.01%
max ← result + 0.01%
||low ← result
||upp ← result
|pri ← result
sec ← 1
|neg%| ← no change
pos% ← no change
|#np ← result * K
#ns ← K
← no change
← no change
|Where, as before:
|= the nominal value for the [ % ] limits
= the negative (positive) percentage error for the
[ % ] limits
= the minimum (maximum) value for the [ > < ]
= the minimum value for the [ > ] limit
= the maximum value for the [ < ] limit
= the primary (secondary) ratio number for the [ % ]
limits - TR or TRL test
|And for the TR or TRL test:
|= the negative (positive) percentage error for the
[ % ] limits
= the number of primary (secondary) turns for the
[ # ] limits
= the ± error number of primary (secondary) turns
for the [ # ] limits
= a factor to make #np and #ns whole numbers in
the range 1 to 99999
1. The conversions in the above table are written in a form to make it easier to understand the conversion process; they are not intended to be exact mathematical formulae.
2. Where possible the measured result is used as the nominal or central value.
For the > and < limits where only one value is required, the measured result simply becomes that value.
For the > < limit where two values are required, the conversion process is in essence to use the single measured result as both the minimum and maximum values. Again, as stated previously for the conversions between the different limit types, because it is not logical to have a minimum and a maximum exactly the same, the two values are made different, but only by a small amount.
If you prefer to use the > < limit, but would like the minimum and maximum values to cover a larger range (for example ±5%), a possible approach is as follows:
Initially choose the % limits before clicking on the Measure button.
After the result has been returned, set the Negative and Positive limits to 5%.
Then change to the > < type of limit, to view the limits in your preferred way.
Another possibility, which you may also choose, is to use this last procedure simply to find approximate values for the minimum and maximum which are 5% from the measured value. You may then enter the actual test limits by rounding up or down to your nearest preferred values.