Electrical Connection; Frequency Converter Operation - Grundfos S Serie Notice D'installation Et De Fonctionnement

8. Electrical connection

Warning
The pump must be connected to an external
mains switch with a contact separation according
to local regulations.
The electrical connection must be carried out in
accordance with local regulations.
The supply voltage and frequency are marked on the pump
nameplate.
The voltage tolerance at the motor terminals must be within
- 10 %/+ 10 % of the rated voltage.
Make sure that the motor is suitable for the power supply
available at the installation site.
The motor is effectively earthed via the power cable and
pipework. The motor top cover is equipped with connections for
external earthing or an equipotential bonding conductor.
Warning
For FM models in dry installation (version D), we
recommend also to connect an external
grounding.
Warning
Before installation and the first start-up of the
pump, check the condition of the cable visually to
avoid short circuits.
The pump must be connected to a motor protective circuit
breaker.
The most commonly used starting methods are direct-on-line
(DOL) start, star-delta (Y/D) start and soft start.
The pump can also be started via frequency converter according
to frequency converter manufacturer's specifications.
The selection of a suitable method depends on several
considerations on usage and mains supply conditions.
When using star-delta starting it is important to
keep switching transient time to a minimum to
avoid high transient torques. We recommend to
Note
Note
use a time relay with switching time max. 50 ms
or according to the starter manufacturer's
specifications.
The wiring diagrams for direct-on-line starting and star-delta
starting are shown in fig. 13 and fig. 14, respectively.
Control
L1
Cable
W2
U1 V1 W1
Fig. 13 Direct-on-line starting
16
L2 L3 PE
U2 V2
PE
M
3
Control
L1
Cable
W2
U1 V1 W1
Fig. 14 Star-delta starting
Control
L1
Cable
U2
U1 V1 W1
Fig. 15 Dual voltage, direct-on-line-starting
(ranges 50 and 54 only)

8.1 Frequency converter operation

In principle, all three-phase motors can be connected to a
frequency converter.
However, frequency converter operation will often expose the
motor insulation system to a heavier load and cause the motor to
be more noisy than usual due to eddy currents caused by voltage
peaks.
In addition, large motors driven via a frequency converter will be
loaded by bearing currents.
For frequency converter operation, please observe the following
information:
Requirements must be fulfilled.
Recommendations ought to be fulfilled.
Consequences should be considered.
8.1.1 Requirements
• The thermal protection of the motor must be connected.
• Peak voltage and dU/dt must be in accordance with the table
below. The values stated are maximum values supplied to the
motor terminals. The cable influence has not been taken into
account. See the frequency converter data sheet regarding the
actual values and the cable influence on the peak voltage and
dU/dt.
Maximum repetitive peak voltage
[V]
850
• Set the frequency converter U/f ratio according to the motor
data.
• Local regulations/standards must be fulfilled.
L2 L3 PE
U2 V2
PE
M
3
L2 L3 PE
V2 W2
PE
M
3
Maximum dU/dt U 400 V
N
[V/μ sec.]
2000