Manual

28 Gossen Metrawatt GmbH
Test Voltage (U
set
= 1000 V)
Test voltage for the inter-turn short circuit measurement is perma-
nently set to 1000 V and cannot be changed.
Connection and Contacting
➭ Make sure that the device under test is voltage-free.
Note
Interference voltage cannot be detected in combination
with the COIL TEST ADAPTER (COIL ADAPTER 50 mH).
➭ Connect the
COIL TEST ADAPTER via the contact protected
plug of its connector cable to the two accessible sockets at
the multimeter: i.e. the red cable to the COIL socket and the
black cable to the  socket.
➭ Connect the two measurement cables to the sockets at the
COIL TEST ADAPTER (identified with motor symbol).
➭ If possible, contact the inductive device under test with op-
tional alligator clips plugged onto the test probes. In the case
of 3-phase motors, for example, contact coil terminals U–V,
V–W and U–W or L1, L2 and L3, one after the other.
Caution: High-Voltage!
Do not touch the conductive ends of the test probes as long as
measurement is active and the Stop softkey is displayed.
A voltage of up to 1200 V is present at the multimeter’s two
enabled output sockets, and as a pulsed voltage at the two
output sockets of the COIL TEST ADAPTER (identified with
motor symbol)
.
Multimeter: You may otherwise be exposed to a current of
2.5 mA (limited in the measuring instrument), and although
this is not life endangering, the resulting electrical shock is
quite discernible.
COIL TEST ADAPTER : Power pulse currents of up to 600 A
can flow from the output sockets.
The device under test can become charged: after each measure-
ment, wait until voltage at the device under test has been
discharged (i.e. until the “Discharging ...” message is cleared
from the display). Touching the device under test may oth-
erwise be life endangering!
Caution: High-Voltage!
In the case of inter-turn short circuit measurements at
transformers, very dangerous high-voltage may occur at the
output side depending on the transformation ratio.
Measured Value Displays
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 or V-W
Vertical axis: Time value in μs
The currently measured time value for the coil selected with the
scroll key is digitally displayed in microseconds to the right of the
bar graph. As of the second measurement, deviation from the
smallest to the largest measured time value is additionally dis-
played as a percentage.
➭ You can delete each measurement in order to repeat it by se-
lecting the desired axis position for U-V, U-W or V-W with the
 or  scroll key and pressing the Delete softkey.
List
You can switch to the list view anytime by pressing the List soft-
key. 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 measurements
appears in the table’s header in terms of deviation as a percent-
age.
➭ You can delete each measurement in order to repeat it by se-
lecting the desired table row for U-V, U-W or V-W with the

or
 scroll key and pressing the Delete softkey.
8.3.1.2 Conducting the Inter-Turn Short Circuit Measurement
➭ Contact the desired coil (e.g. U–V) in order to test for absence
of voltage.
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 along
with the associated time value specified in microseconds to the
right of the bar graph and deviation to the previous measure-
ment is displayed as a percentage for the respective coil L.
➭ Measurement is ended automatically. The measurement can
be aborted by pressing the Stop softkey.*
➭ Before removing the contacting element, allows the coil to dis-
charge via the multimeter (see section 8.3.1.3).
➭ Measurement for motors with three or more coils: Connect the
next coil (e.g. V–W) and repeat the measurement procedure
described above. The next coil is automatically incremented in
the measurement display and activated.
Automatic Evaluation of Measurement Results
Automatic evaluation of measurement results begins when the
second measurement is started. The respective measurement
view (graph or list view) shows maximum deviation to the previous
measurement as a percentage. This permits direct comparison 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 comparison
of all 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 order to start a new measurement series, you can:
- Delete the respectively recorded measurement for each coil
as described under “Measured Value Displays”, or
- Reselect the COIL measuring function with the help of the Func
softkey (or by turning the rotary switch)
- Start a new measurement series by pressing the Restart soft-
key**
*
As of firmware version 1.003.000 – in the case of older firmware versions, end
measurement by pressing the Stop softkey.
Graphic Representation List View