Frequency Converter Operation; Cable Data - Grundfos SE Serie Instrucciones De Instalación Y Operación

7.1 Frequency converter operation

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 may cause the motor to be
more noisy due to eddy currents caused by voltage peaks.
In addition, large motors driven with a frequency converter are
loaded by bearing currents.
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.
• The minimum switching frequency is 2 KHz. The switching
frequency can be variable.
• 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.
Before installing a frequency converter, calculate the lowest
frequency allowed in the installation to avoid zero flow.
• Do not reduce the motor speed to less than 50 %.
• Keep the flow velocity above 3.3 ft/sec (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 motor cable as short as possible. The peak voltage
increases with the length of the motor cable.
• Use input and output filters on the frequency converter.
• Use a screened motor cable if there is a risk that electrical noise
may disturb other electrical equipment.
• Set the frequency converter for constant-torque operation. Pulse
width modulation should be used.
When operating the pump by a frequency converter, observe the
following:
• The locked-rotor torque can be lower depending on the type of
the frequency converter.
• The acoustic 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 frequency converter operation, see the
data sheet and the installation and operating instructions for the
selected frequency converter.
16
Maximum dU/dt U 400 V
N
[V/μ sec.]
2000

7.2 Cable data

Standard H07RN-F
Outer cable diameter
Cable type
[in (mm)]
2
min.
[mm ]
0.83
7 x 4 + 5 x 1.5
(21.2)
0.96
7 x 6 + 5 x 1.5
(24.5)
0.99
7 x 10 + 5 x 1.5
(25.2)
Electromagnetic Compatibility (EMC)
Outer cable diameter
Cable type
[in (mm)]
2
min.
[mm ]
1.03
3 x 6 + 4 x 2.5 + 5
x 0.5
(26.3)
1.03
3 x 10 + 4 x 2.5 + 5
x 0.5
(26.3)
1.03
3 x 16 + 4 x 4 + 5 x
0.5
(26.3)
The minimum size of the ground conductor must be equal
to or bigger than the phase conductor.
The top cover of the explosion-proof pumps is provided
with an external ground terminal to ensure the connection
to the ground. The electrical installation must include an
FM
external connection from this terminal to the ground. The
ground conductor must comply with all electrical safety
regulations in force.
Before installation and the first startup of the pump, check
FM
the condition of the cable to avoid short circuits.
Min. bending
radius
max. [in (mm)]
0.90 2.8
(22.8) (70)
1.03 3.2
(26.1) (80)
1.06 4.4
(26.8) (110)
Min. bending
radius
max. [in (mm)]
1.11 3.6
(28.3) (90)
1.11 4.7
(28.3) (120)
1.11 5.5
(28.3) (140)