Electrical Connection; Motor Protection; Frequency Converter Operation - Grundfos NB Serie Instrucciones De Instalación Y Funcionamiento

10. Electrical connection

The electrical connection must be carried out by a
qualified electrician in accordance with local
regulations.
Warning
Before removing the terminal box cover
and before removing/dismantling the
pump, make sure that the power supply
has been switched off.
The pump must be connected to an
external mains switch.
The operating voltage and frequency are stated on
the nameplate. Make sure that the motor is suitable
for the power supply of the installation site.
The electrical connection must be carried out as
shown in the wiring diagram inside the terminal box
cover.
Warning
Whenever using powered equipment in
potentially explosive environments,
observe the rules and regulations
generally or specifically imposed by the
relevant responsible authorities or trade
organisations.

10.1 Motor protection

Connect three-phase motors to a motor-protective
circuit breaker.
All three-phase Grundfos MG and MMG motors of 3
kW and up incorporate a thermistor. See the
instructions in the motor terminal box.
Carry out the electrical connection as shown in the
wiring diagram on the back side of the terminal box
cover.
Warning
Before starting any repair work on motors
incorporating a thermal switch or
thermistors, make sure that the motor
cannot restart automatically after cooling.
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10.2 Frequency converter operation

All three-phase motors can be connected to a
frequency converter.
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.
A large motor driven via a frequency converter will
be loaded by bearing currents.
Check these operating conditions if the pump is
driven via a frequency converter:
Operating
Action
conditions
2-, 4- and 6-pole
Check that one of the motor
motors, frame
bearings is electrically isolated.
size 280 and
Contact Grundfos.
larger
Fit an output filter between the
motor and the frequency
Noise critical
converter. This reduces the
applications
voltage peaks and thus the
noise.
Particularly noise
critical Fit a sinusoidal filter.
applications
Fit a cable that meets the
specifications laid down by the
frequency converter supplier.
Cable length
The length of the cable between
motor and frequency converter
will affect the motor load.
Check that the motor is suitable
Supply voltage
for frequency converter
up to 500 V
operation.
Fit a sinusoidal filter between
the motor and the frequency
Supply voltage
converter which will reduce the
between 500 V
voltage peaks and thus the
and 690 V
noise, or check that the motor
has reinforced insulation.
Fit a dU/dt filter and check that
Supply voltage of
the motor has reinforced
690 V and higher
insulation.