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0.47 F
0,47 µF
Fig. 6
The motors are wound for direct-on-line starting or star-delta
starting and the starting current is between 4 and 6 times the full
load current of the motor.
The run-up time of the pump is only about 0.1 second. Direct-on-
line starting is therefore normally approved by the electricity sup-
ply authorities.
4.1.1 Frequency converter operation
GRUNDFOS motors:
Three-phase GRUNDFOS motors can be connected to a fre-
quency converter.
Note: If a GRUNDFOS MS motor with temperature transmitter is
connected to a frequency converter, a fuse incorporated in the
transmitter will melt and the transmitter will be inactive. The trans-
mitter cannot be reactivated. This means that the motor will oper-
ate like a motor without a temperature transmitter.
If a temperature transmitter is required, a Pt100 sensor for fitting
to the submersible motor can be ordered from GRUNDFOS.
During frequency converter operation, it is not advisable to run
the motor at a frequency higher than the nominal frequency (50 or
60 Hz). In connection with pump operation, it is important never to
reduce the frequency (and consequently the speed) to such a
level that the necessary flow of cooling liquid past the motor is no
longer ensured.
To avoid damage to the pump part, it must be ensured that the
motor stops when the pump flow falls below 0.1 x nominal flow.
Depending on the frequency converter type, it may expose the
motor to detrimental voltage peaks.
The above disturbance can be abated by installing an RC filter
between the frequency converter and the motor.
Possible increased acoustic noise from the motor can be abated
by installing an LC filter which will also eliminate voltage peaks
from the frequency converter.
For further details, please contact your frequency converter sup-
plier or GRUNDFOS.
4.2 Motor protection
GRUNDFOS MS motors are available with or without a built-in
temperature transmitter.
Motors with a built-in and operational temperature transmitter
must be protected by means of:
•
a motor starter with thermal relay or
•
an MTP 75 and a motor starter with thermal relay or
•
a CU 3 and contactor(s).
1
2
3
4
1. Black
2. Blue
3. Yellow/green
4. Brown
Motors without or with a non-operational temperature transmit-
ter must be protected by means of:
•
a motor starter with thermal relay or
•
a CU 3 and contactor(s).
GRUNDFOS MMS motors have no built-in temperature transmit-
ter. A Pt100 sensor is available as an accessory.
Motors with a Pt100 sensor must be protected by means of:
•
a motor starter with thermal relay or
•
a CU 3 and contactor(s).
Motors without a Pt100 sensor must be protected by means of:
•
a motor starter with thermal relay or
•
a CU 3 and contactor(s).
4.2.1 Required motor starter settings
For cold motors, the tripping time for the motor starter must be
less than 10 seconds at 5 times the rated maximum current of the
motor.
Note: If this requirement is not met, the motor warranty will be
invalidated.
In order to ensure the optimum protection of the submersible
motor, the starter overload unit should be set in accordance with
the following guidelines:
1. Set the starter overload to the rated maximum current of the
motor.
2. Start the pump and let it run for half an hour at normal perform-
ance.
3. Slowly grade down the scale indicator until the motor trip point
is reached.
4. Increase the overload setting by 5%.
The highest permissible setting is the rated maximum current of
the motor.
For motors wound for star-delta starting, the starter overload unit
should be set as above, but the maximum setting should be as
follows:
Starter overload setting = Rated maximum current x 0.58.
The highest permissible start-up time for star-delta starting or
autotransformer starting is 2 seconds.
4.3 Lightning protection
The installation can be fitted with a special overvoltage protective
device to protect the motor from voltage surges in the electricity
supply lines when lightning strikes somewhere in the area, see
fig. 7.
L1
L2
L3
PE
82 50 45
Fig. 7
The overvoltage protective device will not, however, protect the
motor against a direct stroke of lightning.
The overvoltage protective device should be connected to the
installation as close as possible to the motor and always in
accordance with local regulations.
Ask GRUNDFOS for lightning protective devices.
4.4 Cable sizing
Make sure that the submersible drop cable can withstand perma-
nent submersion in the actual liquid and at the actual tempera-
ture.
GRUNDFOS can supply submersible drop cables for a wide
range of installations.
f
7
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