Flowserve PLEUGER - Manual (Page 17)

PLEUGER STANDARD USER INSTRUCTIONS ENGLISH 71569293 01-13
Page 17 of 40
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5.3 Motor protection
To protect the motor against current overload, a
thermal overload relay must be provided. The
tripping time of the relay should have temperature
compensation to allow for variations in ambient
temperature. It should also have accelerated tripping
under single-phase conditions.
Trip reset should only be possible manually.
The setting of the thermal overload relay must be
chosen according to the data sheet provided with the
pump.
For star-delta motor starters, it is important that the
protection relay is in the motor line (see figure 5-3 or
5-9). The adjusted current level will then be 58 % of
the operational current. If the protection relay has
been installed in the power line in exception to this
rule, the adjusted current is the same as the
operational current.
Table 5-1; Overload relay tripping characteristic
I
A
t L
100 mm (4 in.) 150 mm (6 in.) or larger
1.05 x I
E
> 2 hours cold
1.,20 x I
E
< 2 hours warm
5 x I
E
6 x I
E

10

seconds

cold
I
A
= Release current
I
E
= operational current (rated current)
t = Delay time until release
L = Operational temperature before overload
The adjustment of the motor protection relay
(thermally delayed over current release) must be set
according to the value given in the data sheet.
The value given in the data sheet is a standard value
for the operating point. If the actual operational
current in the operating point of the pump is less than
this given value, the motor protection must be
adjusted lower so that there is effective protection
and malfunctions can be indicated in time.
The motor protection adjustment must
never be set higher than the highest permissible
value given in the data sheet. Testing the correct
operation of a motor protection switch by deliberate
single phasing is not permitted!
5.4 Short circuit protection
To prevent a short circuit in the power cable and the
motor, safety precautions must be taken according to
local regulations.
Guide values for safety fuse sizes can be found in the
data sheet.