Operation Manual
GMC-I Messtechnik GmbH 45
Measurements: V/Hz, , , Temp (°C/°F), , M
@UISO
, A/Hz
Automatic Evaluation of the Measuring Results
With the start of the second measurement, the automatic evalua-
tion of the measuring results begins. The analog display* shows
the maximum deviation in percent from all preceding measure-
ments of the U
COIL
measurement series. This allows for a direct
comparison between the first and the subsequent measure-
ments. By establishing a relation between the third measurement
and the results of the preceding measurements, you automatically
receive a concluding comparison of the 3 measurements.
Alternatively, you can measure at all 3 motor coils (star or delta
connected), note down the values and compare them with each
other for conclusion.
The admissible asymmetry depends on the motor type:
A motor with short-circuit rotor will not display any major asym-
metry (typically 1%), whereas a permanently excited motor may
display a certain degree of asymmetry, depending on the rotor
position. At a deviation of more than 10 %, however, there is defi-
nitely a fault in the DUT (e.g. interturn short-circuit).
If a measured value is equal to 0, there is a short-circuit. If there is
no discharge, the measured coil is open.
In order to start a new measurement series, briefly press the
MEA-
SURE | SETUP
key twice or switch to another function (via rotary
switch operation).
* the deviation is presented as a bargraph in function COIL
(default setting), additionally REL is shown.
5.8.3 Ending the Measurement and Discharging
Ð Release the UCOIL ON / OFF key.
After measurement has been completed, any remaining residual
voltage is displayed which may result from cable capacitance.
The instrument’s internal 1 M resistor causes rapid
discharging.
The contact with the motor coils must be maintained.
The falling voltage value can be observed directly at the LCD.
Do not disconnect the device under test until the voltage value has
dropped to < 25 V!
Note
Rotary selector switch position “V1
M
/
M
@UISO
” is
available for the detection of interference voltage prior to
interturn short-circuit measurement.
Use switch position V , V or V in order to perform
precise voltage measurements.
+
–
0V !
Discharge
025.0
U
ISO
V
DC
AC
TRMS
1000V