Grundfos MS 4000, Руководство по эксплуатации продукта

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25
Electrical Installation
MS Motors
Cable Selection
Maximum cable lengths are generally calculated to
maintain 95% of service entrance voltage at the motor
running at maximum nameplate amps, and to maintain
adequate starting torque. Calculations take into
account basic cable resistance, reactance, power
factor and temperature rise cable larger than specified
may always be used, and will reduce power consump-
tion. The wire sizing chart in the Electrical Data section
tabulates copper cable sizes for various cable lengths
vs motor size. The use of power cables smaller than the
minimum sizes as permitted by code or recommended
by Grundfos will generally void the motor warranty.
Understized cable sizes will cause reduced starting
torque and poor motor operation.
Mixed Cable
In a submersible pump installation any combination of
cables sizes may be used provided they do not exceed
the individual maximum conductor ampacity limit and
the aggregate voltage drop does not exceed 5% of the
motor nameplate voltage while operating at full load.
Mixed cable sizes are most often encountered when a
pump is being replaced with a larger horsepower unit.
Cable Splice
When the downhole power cable (drop cable) must be
spliced or connected to the motor leads, it is necessary
that the splice be water tight. Under normal service
conditions, the splice can be made using commercially
available potting compounds, heat shrink or tape. Each
type of splicing methods is affective when made by
competent personnel, potted or head shrink splices are
recommended when submergence pressures exceeds
25 psi (60’). A cable splice should exhibit a minimum
insulation resistance of 10 megohms, measured in a
submerged state after 24 hours in water. A typical low
voltage (< 600V) tape splice is illustrated below in
Figure 9.
When three conductors are encased in a single outer
shealth, tape individual conductors as described, stag-
gering joints. Total thickness of tape should be no less
than the thickness of the conductor insulation.
Motor Lead
Most manufactures will provide a factory motor lead
assembly, pre-potted and designed to provide a water
tight connection between it and the motor terminals.
Typical motor lead length range from 48" to 150" and
are generally spliced to the drop cable immediately
above the pump. Minimum wire sizes (AWG) for factory
provided motor lead assemblies, by nominal motor size
are; 4" - #14 to #12, 6" - #10 to #8, 8" - #4 and 10" - #2.
In general, a motor lead assembly should not be reused
as rubber compounds typically used in there construc-
tion will set with time, making a water tight connection
difficult. Grundfos installation instructions, which
includes pot head connecting torque values and lubri-
cation requirements, should be strictly observed.
Fig. 9
Tape Splice
T
M
03
0
5
64
02
05
STAKED CONNECTOR
RUBBER TAPE
PVC ELECTRICAL TAPE
2"
2"
2"
2"
MS.book Page 25 Wednesday, January 26, 2005 3:25 PM