MEGABRAS TR8703 Manual De Uso página 34

4.2.2.2. Auto Mode
When Auto mode is selected, the instrument requires no user input.
At the end of the test, the Measurement Record is stored in the location
next to the first available location and then will store sequentially.
NOTE: If the previously stored Measurement Record is
encountered, the Auto store mode will skip over and store the new
Measurement Record in the next available location.
4.2.3. VT/PT Excitation Current
Excitation current, displayed in milli-amperes (mA) is the RMS current in
the Primary (H) winding due to test excitation. The loading on the
Secondary (X) winding due to the TR8703 is negligible.
 The TR8703 uses a maximum of 32 Vrms excitation voltage for testing.
The displayed excitation current will almost always be a small fraction
of transformer no-load excitation at full (rated) voltage. Most
transformers will require less than 100 mA
 If you are presently using a ratiometer that employs secondary (X) side
excitation (e.g. common hand-cranked instruments) in step-up mode,
the current may be much higher than what the TR8703 displays
 This is normal and results directly from the fact that in most step-down
transformers, the Primary (H) side has a much higher impedance than
its associated Secondary (X) winding
4.2.4. Continuity Test
The Continuity Test function of the TR8703 serves as a useful means of
identifying open primary and secondary windings, high resistance
connections, open circuit breakers and blown fuses. When selected, the
TR8703 checks for continuity between its Secondary (X) and Primary (H)
cables.
 The TR8703 will indicate OPEN for circuits >4 KΩ and CONT for
circuits <4 KΩ. Check these values. A small fraction of transformers
(High inductance or high winding Ohmic DC resistance) may appear
open
 The instrument checks for Secondary (X) connections first. Even if it is
found open, it continues to check Primary (H) connections. Regardless
of the outcome, the instrument proceeds to perform pre-test checks.
Following the pre-test checks, if either X or H or both were found to be
OPEN, the instrument will display the appropriate error message.
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