Frequency Converter Operation - Grundfos SRG Serie Instrucciones De Instalación Y Funcionamiento

4.4.4 Frequency converter operation

All SRG pumps are designed for frequency converter
operation for energy saving and for soft start. For
frequency converter operation, please observe the
following information:
• Requirements must be fulfilled.
• Recommendations ought to be fulfilled.
• Consequences must be considered.
4.4.5 Requirements
• 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.
3x400V 50 Hz:
Maximum
repetitive
Product type
peak voltage
[V]
SRG.xx.30
1500
SRG.35.50
SRG.xx.xx 1000
• In case the above values are too high, a dU/dt
filter could prevent the voltage peaks.
• The thermal protection of the motor must be
connected.
• Do not exceed the frequency indicated on the
nameplate. Otherwise, there is a risk of motor
overload.
• Local regulations or standards must be fulfilled.
12
4.4.6 Recommendations
• Do not reduce the motor speed to less than 30 %
of the rated speed.
• Do not set any slip compensation, as it may lead
to an over speed and therefore to motor
overload.
• Set the frequency converter U/f ratio to a linear
relation, and use the data from the motor
nameplate for settings about rated current,
power, voltage and frequency.
• Use input and output filters on the frequency
converter. See data sheet for the frequency
converter used.
• Keep the power cable as short as possible. The
peak voltage will increase with the length of the
power cable. See data sheet for the frequency
converter used.
• Use a screened power cable if there is a risk that
electrical noise can disturb other electrical
equipment. See data sheet for the frequency
converter used.
Maximum
dU/dt [V/μs]
• Ramp-up and ramp-down time must be at least 5-
10 seconds.
4.4.7 Consequences
15000
When operating the product via a frequency
converter, please be aware of these possible
3000
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 for advice as to how to
reduce the acoustic noise.