Variable-Frequency Drive Operation; High-Voltage Surge Arresters - Grundfos SP Instrucciones De Instalación Y Funcionamiento

6.6.3 Variable-frequency drive operation

Grundfos motors:
Three-phase Grundfos motors can be connected
to a VFD (variable frequency drive).
If a Grundfos MS motor with
temperature transmitter is
connected to a VFD, and if the
motor becomes overheated, a fuse
incorporated in the transmitter will
Note
melt and the transmitter will be
inactive. The transmitter cannot be
reactivated. This means that from
that point on, the motor will
operate like a motor without a
temperature transmitter.
If a new 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 low level that
the necessary flow of cooling liquid past the
motor is no longer ensured.
To avoid damage to the pump, it must be
ensured that the motor stops when the pump
flow falls below 0.1 x rated flow.
Depending on the VFD type, it may expose the
motor to detrimental voltage peaks.
Warning
Motors, type MS 402, 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.
We recommend you to protect
other motors against voltage peaks
higher than 850 V.
The above disturbance can be abated by
installing an RC filter between the VFD 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
VFD.
For further details, please contact your VFD
supplier or Grundfos.
Other motor manufacturers than Grundfos
Please contact Grundfos or the motor
manufacturer.

6.6.4 High-voltage surge arresters

Use a high-voltage surge arrester to protect the
motor against lightning and switching surges.
Lightning voltage surges in power lines are
caused when lightning strikes somewhere in the
area.
Switching surges are caused by the opening and
closing of switches on the main high-voltage
distribution power lines.
Install the correct voltage-rated surge arrester
on the supply side of the control box. see fig.
and fig. 14. The arrester must be grounded in
accordance with the National Electrical Code
and local codes and regulations.
Single-phase
power supply
Lightning
arrester
Fig. 13 Single-phase installation
Three-phase power supply
Ground
Lightning
arrester
T1 T2
To MS motor
Fig. 14 Three-phase installation
The warranty on all three-phase
submersible motors will become
VOID if:
1. The motor is operated with
single-phase power through a
phase converter.
2. Three-leg ambient compensated,
Note
extra quick-trip overload protectors
are not used.
3. Three-phase current imbalance
is not checked and recorded.
See section 7. Startup
4. High-voltage surge arresters are
not installed.
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Ground
True
grounding
point
Pump control
panel
Install lightning
protectors
before fuses or
circuit breaker
T3
True grounding
point
on page 15.
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