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

4.2.1 Cable data

Standard H07RN-F
SE, SL
Outer cable diameter
Cable type
pump
range
[hp (kW)]
2
[mm ]
7 x 4 + 5 x 1.5
12-42
7 x 6 + 5 x 1.5
(9-30)
7 x 10 + 5 x 1.5
EMC
SE, SL
Outer cable diameter
Cable type
pump
range
[hp (kW)]
2
[mm ]
3 x 6 + 5 x 1
12-42
3 x 10 + 5 x 1
(9-30)
3 x 16 + 5 x 1
The minimum size of the earth conductor must be
equal to or bigger than the phase conductor.
The top cover of explosion-proof pumps is provided
with an external earth terminal to ensure the
connection to earth. The electrical installation must
FM
include an external connection from this terminal to
earth. The earth conductor must fulfil all electrical
safety regulations in force.

4.2.2 Frequency converter operation

In principle, all three-phase motors can be connected to a
frequency converter.
However, 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.
In addition, large motors driven via a frequency converter will be
loaded by bearing currents.
For frequency converter operation, please observe the following:
• Requirements must be fulfilled.
• Recommendations ought to be fulfilled.
• Consequences should be considered.
10
Min.
bending
[in (mm)]
radius
min. max. [in (cm)]
0.83 0.91 4.7
(21.0) (23.0) (12.0)
0.94 1.05 5.1
(23.8) (26.8) (13.0)
0.96 1.08 5.5
(24.5) (27.5) (14.0)
Min.
bending
[in (mm)]
radius
min. max. [in (cm)]
0.96 1.07 5.5
(24.5) (27.5) (14)
0.97 1.08 5.5
(24.7) (27.7) (14)
0.98 1.1 5.5
(24.9) (27.9) (14)
Requirements
• 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 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 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/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 30 Hz.
• Keep the flow velocity above 3.3 ft/sec (1 m/sec).
• 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 as
this may cause motor overload.
• Keep the motor cable as short as possible. The peak voltage
will increase with the length of the motor cable. See data sheet
for the frequency converter used.
• Use input and output filters on the frequency converter. See
data sheet for the frequency converter used.
• Use a screened motor cable if there is a risk that electrical
noise may disturb other electrical equipment. See 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 bearings and 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