Frequency Converter Operation - Grundfos BMEX Series Montage- Und Betriebsanleitung

7.2.1 Frequency converter operation

Three-phase Grundfos MS motors can be connected to a
frequency converter.
If an MS motor with temperature transmitter is
connected to a frequency converter, a fuse
incorporated in the transmitter will melt and the
Note
transmitter will be inactive. The transmitter cannot be
reactivated. This means that the motor will operate
like a motor without a temperature transmitter.
If a temperature transmitter is required, a Pt100 sensor for fitting
to the motor can be ordered from Grundfos.
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
Caution
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.
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.
7.2.2 Motor protection
The motor must be connected to an effective motor starter which
must protect the motor against damage from voltage drop, phase
failure, overload and a locked rotor.
In power supply systems where undervoltage and variations in
phase symmetry may occur, a phase failure relay should also be
fitted. See section 23. Checking motor and
The control circuit must always be made in such a way that all
pumps of the BMEX system are stopped if one pump fails.
10
7.2.3 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
I
SFA
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
2. Start the BM hp circulation pump, and let it run for half an hour
3. Slowly grade down the scale indicator until the motor trip point
4. Increase the overload setting by 5 %, but not higher than the
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
The maximum permissible run-up changeover time for star-delta
starting is 2 seconds.
cable, point 1.
) of the motor. See motor nameplate.
If this requirement is not met, the motor warranty will
Note
be invalidated.
motor.
at normal performance. See section
pump.
is reached.
rated current (I /I ) of the motor.
1/1 SFA
/
1/1
/I ) of the
1/1 SFA
9.7 BM hp circulation
/I ) x 0.58.
1/1 SFA