Frequency Converter Operation; Starting Up The Product - Grundfos S2 Instrucciones De Instalación Y Funcionamiento

4.3 Frequency converter operation

For frequency converter operation, please observe the following
information:
• Requirements must be fulfilled.
• Recommendations ought to be fulfilled.
• Consequences should be considered.
When the motor is driven via frequency converter,
FM
the temperature class of explosion-proof pumps must
be T3.
Requirements
• The thermal protection of the motor must be connected.
• The 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
• If the pump is an FM-approved pump, check if the FM
certificate of the specific pump allows the use of a frequency
converter.
• Set the frequency converter U/f ratio according to the motor
data.
• Local regulations/standards must be fulfilled.
Recommendations
Before installing a frequency converter, calculate the lowest
allowable frequency in the installation in order to avoid zero flow.
• Do not reduce the motor speed to less than 60 % of rated
speed or 30 Hz.
• Keep the flow velocity above 3.3 ft/s (1 m/s).
• Let the pump run at rated speed at least once a day in order to
prevent sedimentation in the piping system.
• Do not exceed the frequency indicated on the nameplate. If
you do, there is risk of motor overload.
• Keep the power cables as short as possible. The peak voltage
will increase with the length of the power cables. See the data
sheet for the frequency converter used.
• Use input and output filters on the frequency converter. See
the data sheet for the frequency converter used.
• Use screened power cables if there is a risk that electrical
noise can disturb other electrical equipment. See the data
sheet for the frequency converter used.
Consequences
When operating the pump via a frequency converter, please be
aware of these possible consequences:
• The locked-rotor torque will be lower. How much lower will
depend on the frequency converter type. See the installation
and operating instructions for the frequency converter used for
information on the locked-rotor torque available.
• The working condition of the bearings and the shaft seal may
be affected. The possible effect will depend on the application.
The actual effect cannot be predicted.
• The acoustic noise level may increase. See the installation
and operating instructions for the frequency converter used for
advice as to how to reduce the acoustic noise.
Maximum dU/dt U 400 V
N
[V/μ sec.]
2000

5. Starting up the product

You can start the pump using either direct-on-line (DOL) starting
or star-delta (Y/D) starting. The selection of starting method
depends on several considerations of usage and main power
supply.
If you use star-delta starting, keep the switching
transient time to a minimum to avoid high transient
torques.
We recommend that you use a time relay with a switching time of
maximum 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. 14 and fig. 15. See also the wiring
diagram for sensors in fig. 13.
Control
cable
L1
W2
U1
Fig. 14 Direct-on-line starting
Control
cable
L1 L2
W2
U1 V1 W1
M
3
Fig. 15 Star-delta starting
L2 L3 PE
U2 V2
V1 W1 PE
M
3
L3 PE
U2 V2
PE
13