8
9.2.1 Frequency converter operation
Three-phase Grundfos MS motors can be connected to a
frequency converter.
If a temperature transmitter is required, a Pt100 sensor for fitting
to the motor can be ordered from Grundfos.
The permissible frequency ranges are 30-50 Hz and 30-60 Hz,
respectively.
During starting, the maximum acceleration time from 0 to 30 Hz is
1 second.
During stopping, the maximum deceleration time from 30 to 0 Hz
is 1 second.
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
supplier or Grundfos.
9.2.2 Motor protection
See section
The control circuit must always be made in such a way that all
pumps of the BMPX system are stopped if one pump fails.
9.2.3 Setting of motor starter
For cold motors, the tripping time for the motor starter must be
less than 10 seconds (Class 10) at 5 times the rated current
(I
1/1
/I
SFA
) of the motor. See motor nameplate.
To ensure optimum protection of the motor, the starter overload
unit should be set in accordance with the following guidelines:
1. Set the starter overload to the rated current (I
1/1
/I
SFA
) of the
motor.
2. Start the BM hp circulation pump and let it run for half an hour
at normal performance. See section
3. Slowly grade down the scale indicator until the motor trip point
is reached.
4. Increase the overload setting by 5 %, but not higher than the
rated current (I
1/1
/I
SFA
) 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 current (I
1/1
/I
SFA
) x 0.58.
The maximum permissible run-up changeover time for star-delta
starting is 2 seconds.
10. Before starting the BMPX
Check the following:
•
Electricity supply in accordance with nameplate.
•
Pipework according to the diagram, fig. 12.
•
Functionality of the solenoid valve (BM hp circulation pump
only).
•
Functionality of the low-pressure switch on the inlet side of the
BMP hp feed pump.
See set value in the installation and operating instructions for
BMP pumps.
In addition, flush all pipes to remove all impurities before
connecting the units.
Fig. 12
Piping and instrumentation diagram
Caution
If an 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 transmitter
cannot be reactivated. This means that the motor
will operate like a motor without a temperature
transmitter.
Caution
During frequency converter operation, it is not
advisable to run the motor at a frequency higher
than the rated 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.
Note
If this requirement is not met, the motor warranty
will be invalidated.
T
M
03
9
6
9
6
43
07
Pos.
Description
P1
Sea-water feed pump
P2
Cleaning/flush pump
P3
BMP hp feed pump
P4
BM hp circulation pump with variable-frequency drive
V1
Three-way valve for feed water and cleaning
V2
Control valve for controlling pressure and flow
V3
Low-pressure reject-water valve
V4
Solenoid valve
V5
Control valve for controlling pressure and flow
V6
Cleaning/flush valve
CV1
Non-return valve
FM1-3
Flowmeter for balancing the system
X1
X-Changer
HP
High-pressure switch
LP
Low-pressure switch
S1
Pressure relief valve
P3
CV1
CV1
V3
V1
V2
HP
S1
LP
P1
P2
P4
FM3
FM2
FM1
V5
V4
X1
V6
Semi-permeable membrane
