Frequency Converter Operation; Protection And Control Functions; Motor Protection Devices; Pump Controller - Grundfos S2 Série Mode D'emploi

6.2 Frequency converter operation

Connect pumps installed in hazardous locations to a
FM
control box with a motor protection relay with an IEC trip
class 10.
In principle, all three-phase motors can be connected to a
frequency converter.
However, frequency converter operation often exposes the motor
insulation system to a heavier load and cause the motor to be more
noisy than usual.
In this product range, only negligible amounts of bearing currents
occur during the use of frequency converter.
For frequency converter operation, observe the following:
• 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 is not taken into account.
See the frequency converter data sheet regarding the actual
values and the cable influence on the peak voltage and dU/dt.
• Minimum switching frequency is 2 kHz. Variable switching
frequency is accepted.
• If the pump is an Ex-approved pump, check if the Ex 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 or standards must be complied with.
• Before installing a frequency converter, calculate the lowest
permissible frequency in the installation to avoid zero flow.
• Do not reduce the motor speed to less than 50 %.
• Keep the flow rate above 1 m/sec.
• Let the pump run at rated speed at least once a day to prevent
sedimentation in the pipe network.
• Do not exceed the frequency indicated on the nameplate as this
may cause motor overload.
• Keep the power cable as short as possible. The peak voltage
increases with the length of the power cable.
• Use input and output filters on the frequency converter.
• Use a screened power cable if there is a risk that electrical
noise may disturb other electrical equipment.
• Set frequency converter for constant-torque operation. Pulse
width modulation should be used.
When operating the pump by a frequency converter, consider the
following:
• The locked-rotor torque can be lower depending on the
frequency converter type.
• The noise level may increase. See the installation and operating
instructions for the selected frequency converter.
Maximum repetitive peak voltage
[V]
850
Frequency converter use may reduce the lifespan of the
bearings and the shaft seal, depending on the operating
mode and other circumstances.
For more information about the pump speed/torque curves
when operated by a frequency converter,visit Grundfos
Product Center at https://product-selection.grundfos.com.
For more information about the frequency converter operation, see
the data sheet and the installation and operating instructions for the
selected frequency converter.
Maximum dU/dt U 400 V
N
[V/μ sec.]
2000

7. Protection and control functions

7.1 Motor protection devices

The motors have three thermal protectors and two moisture
switches connected in series. Protectors and switches are
connected in two separate circuits. The thermal protectors are
reversible, and the moisture switches are irreversible. The thermal
protection circuit, conductors 1 and 3, and the moisture protection
circuit, conductors 2 and 3, have separate outputs to enable
separate alarms if the motor is overheated or affected by moisture.
All other sensor connections are either led out of the motor, sensor
version D, through conductors 4 to 9, or connected to the sensor
board, sensor version B, and led out of the motor through
conductors 4 and 5.

7.2 Pump controller

The liquid level can be controlled by Grundfos LC 231 and LC 241
level controllers. The pumps are protected by thermal switches
connected to the LC controller or a CU 100 control unit.

7.3 IO 113

IO 113 forms the interface between a Grundfos sewage and
wastewater pump with analog and digital sensors and the pump
controller. The most important sensor data are indicated on the front
panel.
One pump can be connected to an IO 113 module.
With the sensors, IO 113 forms a galvanic separation between the
motor voltage in the pump and the controller connected.
IO 113 is capable of the following as standard:
• protect the pump against overheating
• monitor the status of:
- motor winding temperature
- leakage through WIO sensor
- moisture in the pump.
• measure the stator insulation resistance
• stop the pump in case of alarm
• remotely monitor the pump through RS-485 communication,
Modbus or GENIbus
• control the pump through a frequency converter.
Combined with SM 113, IO 113 can monitor the bearing
temperature and the rotor speed when the motor is switched off.
7.3.1 Galvanic separation
Double-insulated sensors for all measurements ensure the
electrical safety. Furthermore, there is a galvanic separation inside
IO 113.
7.3.2 Measurement of insulation resistance
IO 113 measures the insulation resistance between a stator winding
and earth:
• Resistance above 10 megaohms is ok.
• Resistance between 10 and 1 megaohms causes a warning.
• Resistance below 1 megaohm causes an alarm.
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