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10 3 Resistance measurement
We recommend checking the winding and insulation
resist ance before connecting the pump to the controller. For
a submersible pump these measurements should be done
BEFORE lowering the pump into the well.
WARNING – Before starting any work
on the pump system, make sure that
the electricity supply has been
switched off and that it cannot be
accidentally switched on!
To measure the winding and insulation resistance discon-
nect all motor leads from the controller. A good quality
Multimeter is necessary to measure the phase-to-phase re-
sistance with an accurancy to the first decimal place. ("0.1
Ohms"). It is also adviseable to consider the resistance of
the multimeter leads when measuring very low values:
ƒ Hold the tips of the multimeter together and note the
value.
ƒ Always substract this value from your motor resistance
measurements!
Table 7: Motor cable resistance
Cable
4 mm
/ AWG 11
2
6 mm
/ AWG 9
2
10 mm
2
/ AWG 7
16 mm
/ AWG 5
2
BERNT LORENTZ GmbH & Co. KG Kroegerskoppel 7, 24558 Henstedt-Ulzburg, Germany, Tel. +49 (0) 4193 7548 - 0, Fax - 29, www.lorentz.de
All specifi cations and information are given with good intent, errors are possible and products may be subject to change without notice. Pictures may
differ from actual products depending on local market requirements and regulations.
Winding resistance
1.
Set the multimeter to "resistance measurement" and
select the lowest measuring range.
2.
All PSk2 motors are 3-phase motors. Measure the
resistance of phase-to-phase: L1-L2, L2-L3, L3-L1.
Make sure there is good contact between the probes
and the cable.
3.
The deviation between the phases should be within
10 %. If the deviation is too high, the reason is likely
a damaged submersible cable or a faulty cable splice.
4.
The absolute value is made up of the resistance of
the motor winding and the submersible cable. The
resistance of the submersible cable depends on its
length and size. For copper cable, the values of the
table below, "Table 7: Motor cable resistance", can
be used as a rough approximation.
Example:
ƒ Motor:
AC DRIVE SUB 6" 7.5 kW 1.8 Ω
ƒ Motor cable:
150 m and 6 mm
Calculation of expected phase-to-phase resistance:
= 1.8 Ω + 2 × 150 m × 0.25 Ω / 100 m
= 1.8 Ω + 2 × 0.375 Ω
= 1.8 Ω + 0.75 Ω
= 2.55 Ω
= ~ 2 6 Ω
The real measured values can be different, depending on
the measurement equipment and materials that are used.
This is just an approximation.
Resistance
[Ω / 100 m]
0.40
0.25
0.17
0.10
0.25 Ω / 100 m
2
19
Insulation resistance
Use a Megohmmeter at 500 –1,000 V.
Measure each phase to ground. Connect one test prod to
the phase hold the other test prod to the pipe work, or if
plastic pipes are used to the ground wire.
If the insulation resistance is below 0.5 MΩ ,the motor
cable must be ckecked for damage.
Sun. Water.
Life.
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