Manual

32 Gossen Metrawatt GmbH
Measured Value Display
Graphic
Graphic representation is used as a standard feature for the mea-
surement view. If the instrument is in the list view, you can switch
to the graphic display by pressing the Graphic softkey.
Horizontal axis: Coil U-V, U-W, V-W
Vertical axis: Time value in μs
The currently measured time value for the coil selected at the mul-
timeter is digitally displayed in microseconds to the right of the bar
graph. As of the second measurement, deviation from the small-
est to the largest measured time value is additionally displayed as
a percentage.
➭ Each individual measurement (bar) can be deleted from the
graphic in order to repeat it by first of all selecting the desired
coil (U-V, U-W, V-W, V-U etc.) with the adapter’s rotary switch,
and then pressing the Delete softkey.
List
You can switch to the list view at any time by pressing the List
softkey. In this case, deviation from the previous time values, as
well as date and time of the measurement, are listed along with
the respective time values. The final comparison of all measure-
ments appears in the table’s header.
The first line (no. 1) shows the target values for coil U-V/V-U, the
second line (no. 2) for coil U-W/W-U and the third line (no. 3) for
coil V-W/W-V.
➭ You can delete the respective measured value pair (for positive
and negative polarity) from the list in order to repeat the mea-
surement by first of all selecting the corresponding coil,
namely U-V and V-W, U-W and W-U or
V-W and W-V, and then pressing the Delete softkey.
8.3.2.2 Conducting the Inter-Turn Short Circuit Measurement
➭ Select the desired inductance range (High or Low) with the
help of the rocker switch on the adapter (see “Selecting the
Inductance Range” on page 31).
➭ Set the adapter’s rotary switch to the desired coil. For exam-
ple, start with the first switch setting: U-V.
➭ Contact winding terminals U, V and W or L1, L2 and L3.
Attention!
!
Perform measurement with self-retaining contacting de-
vices, for example alligator clips. Poor contact may result
in sparking and if the contacting element slips off of the
device under test, the inspector is exposed to life-threat-
ening danger!
➭ Activating the Inter-Turn Short Circuit Measurement
Activate the measurement by pressing the Start softkey. The
high-voltage symbol next to the battery level display blinks
during measurement.
➭ Measurement is stable as soon as a bar graph appears
in the graphic representation along with the associated time
value specified in microseconds to the right of the bar graph
and deviation to the previous measurement is displayed as a
percentage, or
the time value and the deviations to the previous measure-
ments are indicated in the respective line in the list view:
U-V, U-W, V-W: green bar in graphic view,
time value for +COIL in list view
V-U, W-U, W-V: orange bar in graphic view,
time value for -COIL in list view
➭ After measurement has been completed, wait until voltage at
the device under test has been discharged. The next mea-
surement may not be started until after the “Select next switch
position at COIL Adapter” prompt appears, which is displayed
subsequent to the “Discharging – please wait” message.
Attention!
!
Turning the rotary switch or throwing the rocker switch
during a running measurement can damage or destroy
the COIL ADAPTER XTRA.
➭ Repeat the above described measuring procedure by setting
the rotary switch to the corresponding position.
➭ The multimeter detects the selected position and automati-
cally performs the measurement. If measurement is stable,
the next measurement results are displayed.
➭ Complete the procedure by conducting measurements, one
after the other, for all of the coils or rotary switch positions as
described above.
Automatic Evaluation of Measurement Results
Automatic evaluation of measurement results begins when the
second measurement is started. The respective measurement
view (graphic or list view) shows maximum deviation from the pre-
vious measurement as a percentage. This permits direct compar-
ison of the first and all subsequent measurements. Due to the fact
that the third measurement is then compared with the results of
both previous measurements, you automatically get a final com-
parison of all three measurements.
The list view permits a final comparison of all measured motor
coils (star or delta connection).
Permissible asymmetry depends on motor type:
A motor with squirrel-cage rotor demonstrates only minimal
asymmetry (typically 1%). If deviation is greater than 10%, the de-
vice under test is faulty (e.g. inter-turn short circuit).
If any of the time values is 0, there’s a short-circuit. If no discharg-
ing takes place, the measured coil is interrupted (display: OL).
In the case of permanent-field motors, inter-turn short circuit
measurement is dependent on rotor position. This also applies to
squirrel cage motors with large inductances which result in more
frequently occurring remanence. First of all, measurement must
be performed at each coil with positive polarity (U-V, U-W, V-W).
Afterwards, each coil is measured once again with reversed po-
larity (V-U, W-U, W-V). The rotary switch on the COIL ADAPTER
XTRA must be set to the respective position to this end. As a re-
sult, there’s no need to reconnect the terminals at the COIL
Adapter to the motor coil. The instrument generates a mean value
based on both measurement results which, to a great extent, is
independent of rotor position.
Graphic Representation List View