Frequency Converter Operation; Motor Protection - Grundfos SP Serie Montage- Und Betriebsanleitung

The required voltage quality for Grundfos MS and MMS
submersible motors, measured at the motor terminals, is
– 10 %/+ 6 % of the nominal voltage during continuous operation
(including variation in the supply voltage and losses in cables).
Furthermore, it must be checked that there is voltage symmetry in
the electricity supply lines, i.e. same difference of voltage
between the individual phases, see also section 10. Checking of
motor and cable, point 2.
Warning
The pump must be earthed.
The pump must be connected to an external
mains switch with a minimum contact gap of
3 mm in all poles.
If Grundfos MS motors with a built-in temperature transmitter
(Tempcon) are not installed together with a MP 204 or similar
Grundfos motor protection, they must be connected to a 0.47 μF
capacitor approved for phase-phase operation (IEC 384-14) to
meet the EC EMC directive (2004/108/EC). The capacitor must
be connected to the two phases to which the temperature
transmitter is connected, see fig. 9.
0.47 μF
0,47 µF
Fig. 9 Connection of capacitor
Colours of the leads
Lead Flat cable
1 = L1 Brown
2 = L2 Black
3 = L3 Grey
4 = PE Yellow/green
The motors are wound for direct-on-line starting or star-delta
starting and the starting current is between 4 and 6 times the
rated 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
supply authorities.

5.1.1 Frequency converter operation

Grundfos motors
Three-phase Grundfos motors can be connected to a frequency
converter.
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
Caution
transmitter cannot be reactivated. This means
that the motor will operate like a motor without
a temperature transmitter.
10
If a temperature transmitter is required, a Pt100 sensor for fitting
to the submersible motor can be ordered from Grundfos.
Caution
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.
It is recommended to protect other motors against voltage peaks
higher than 850 V.
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
1
2
3 by installing an LC filter which will also eliminate voltage peaks
4
from the frequency converter.
Grundfos recommends the installation of an LC filter when a
frequency converter is used. See also section 5.7.6 Frequency
converter.
For further details, please contact your frequency converter
supplier or Grundfos.
Other motor makes than Grundfos
Please contact Grundfos or the motor manufacturer.

5.2 Motor protection

5.2.1 Single-phase motors
Single-phase MS 402 submersible motors, incorporate a
thermal switch and require no additional motor protection.
Single-phase MS 4000 submersible motors, must be
protected. A protective device can either be incorporated in a
Single leads
control box or be separate.
Black
Franklin 4" PSC motors must be connected to a motor starter.
Yellow
5.2.2 Three-phase motors
Red
Grundfos MS motors are available with or without a built-in
Green
temperature transmitter.
Motors with a built-in and operational temperature transmitter
must be protected by:
•
•
Motors without or with a non-operational temperature
transmitter must be protected by:
•
•
Grundfos MMS motors have no built-in temperature transmitter.
A Pt100 sensor is available as an accessory.
Motors with a Pt100 sensor must be protected by:
•
•
Motors without a Pt100 sensor must be protected by:
•
•
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.
Warning
MS 402 motors for supply voltages up to and
including 440 V (see motor nameplate) must be
protected against voltage peaks higher than
650 V (peak value) between the supply terminals.
Warning
When the motor has been thermally switched off,
the motor terminals are still live.
When the motor has cooled sufficiently, it will
restart automatically.
a motor starter with thermal relay or
an MP 204 and contactor(s).
a motor starter with thermal relay or
an MP 204 and contactor(s).
a motor starter with thermal relay or
an MP 204 and contactor(s).
a motor starter with thermal relay or
an MP 204 and contactor(s).