Electrical Connections; Frequency Converter Operation - Grundfos TP Series Installation And Operating Instructions Manual

7.5.2 Vibration dampers
To prevent vibrations from being transmitted to the
building, it is recommended to isolate the pump
foundation from buildings by means of vibration
dampers. In order to select the right vibration
damper, the following details are required:
• Forces transferred through the damper.
• Motor speed. In the case of speed control, this
must also be taken into account.
• Desired dampening in %
(recommended value 70 %).
The selection of vibration damper differs from
installation to installation. A wrong damper may in
certain cases increase the vibration level.
Vibration dampers should therefore be sized by the
supplier.
If the pump is installed on a foundation with vibration
dampers, expansion joints must be fitted on both
sides of the pump. This is very important to ensure
that the pump is not "hanging" from the flanges.

8. Electrical connections

The electrical connections should be carried out by
an authorized electrician in accordance with local
regulations.
Warning
Before removing the terminal box cover
and before any removal/dismantling of
the pump, make sure that the electricity
supply has been switched off.
The pump must be connected to an
external mains switch.
The operating voltage and frequency are marked on
the nameplate. Make sure that the motor is suitable
for the electricity supply on which it will be used.
The motor must be connected to a motor starter.
Motors of 3 kW and up incorporate thermistors
(PTC). The thermistors are designed according to
DIN 44082. The motor starter and the thermistors
must be connected in series. Consequently, the
motor will not be started until it has cooled to normal
temperature.
The terminal box can be turned in 30 ° or 45 ° steps,
depending on pump size.
Remove the bolts securing the motor to the pump.
Turn the motor to the required position. Replace and
tighten the bolts.
The electrical connection should be carried out as
shown in the diagram inside the terminal box cover.
Do not start the pump until it has been
Caution
filled with liquid and vented.
14

8.1 Frequency converter operation

Grundfos motors:
All three-phase Grundfos motors from frame size 90
and up can be connected to a frequency converter.
The connection of a frequency converter will often
have the effect that the motor insulation system is
loaded more and that the motor will be more noisy
than during normal operation. In addition, large
motors are loaded by bearing currents caused by the
frequency converter.
In the case of frequency converter operation, the
following should be considered:
• In 2- and 4-pole motors of 110 kW and up and
6-pole motors of 75 kW and up, one of the motor
bearings should be electrically isolated to prevent
damaging currents from passing through the
motor bearings.
• In the case of noise critical applications, the
motor noise can be reduced by fitting a dU/dt
filter between the motor and the frequency
converter. In particularly noise critical
applications, it is recommended to fit a sinusoidal
filter.
• The length of the cable between motor and
frequency converter affects the motor load.
It should therefore be checked that the cable
length meets the specifications laid down by the
frequency converter supplier.
• For supply voltages between 500 and 690 V,
either a dU/dt filter should be fitted to reduce
voltage peaks or a motor with reinforced
insulation should be used.
• For supply voltages of 690 V, a motor with
reinforced insulation should be used and a dU/dt
filter should be fitted.
Other motor makes than Grundfos:
Please contact Grundfos or the motor manufacturer.