EN
22/08/22
User Manual Resistance Meter 30A/2
–
60A/2
–
80A/2 62000640_08_
8
1.
INTRODUCTION
RM30/2, RM60/2 and RM80/2 are professional instruments which allows to measure the stator
windings resistance of three-phase or single-phase motors, or of another alternating load during
the working.
In this way it is possible to measure the temperature variation of the load under testing through
the following simple formula:
t =
Where:
∆
t = over rising temperature
R1 = test beginning resistance
R = test end resistance
t1 = test beginning ambient temperature
t2 = test end ambient temperature
α
= temp. Coefficient (
α
cu = 234.5)
1.1.
MAIN FEATURES
1.1.1.
Resistance Measurement
The resistance meter, as mentioned before, is capable of measuring the winding resistance of a
working single-phase or three-phase motor/load.
In case of a three-phase load, the instrument supplies the digital reading of the total resistance
between two of the three phases U, V, W, by allowing to choose, through proper commutator,
between the couple U-V and the couple U-W. This allows to measure, especially in case of not
symmetric windings, the different heating without discontinuing the test for wiring changing.
In case of capacitor single-phase motor, the same commutator allows to choose between the
reading of the main and auxiliary phase resistance.
1.1.2.
Function VOLT
A working condition (commutator on
VOLT
) is foreseen in which the load is directly fed and the
instrument measures the input voltage between the two phases.
The choice of this position is requested when, for example during the motor starting, high current
peaks may occur, higher than the limits allowed by the instrument.
R
2
– R
1
——— (
+ t
1
) - ( t
2
- t
1
)
R
1
