Wilo Rexa CUT GE, Installation And Operating Instructions Manual

Page: 163 / 1148

Appendix en
Installation and operating instructions Wilo-Rexa CUT GE 163
Geomet-coated screws (strength 10.9) with Nord-Lock washer
Threaded Tightening torque
Nm kp m ft·lb
M12
126.5 12.90 93.3
M16
155 15.81 114.3
M20
265 27.02 195.5
13.2 Operation with frequency con-
verter
The motor in series design (confirming to IEC 60034‑17) can be operated with a fre-
quency converter. Contact customer service if the rated voltage is over 415 V/50 Hz or
480 V/60 Hz. Because of the additional heating caused by harmonics, the rated power
of the motor must be around 10 % more than the power requirement of the pump. For
frequency converters with a low-harmonic output, it may be possible to reduce the
10 % power reserve. A reduction of the harmonic waves is achieved with output filters.
The frequency converter and filter must be compatible.
The configuration of the frequency converter depends on the rated motor current. Care
must be taken to ensure that the pump operates without jerking or vibration, especially
in the lower speed range. Otherwise, the mechanical seals can leak or be damaged. The
flow rate in the pipe must also be observed. If the flow rate is too low, the greater the
risk is of solids depositing in the pump and piping. A minimum flow rate of 0.7 m/s
(2.3 ft/s) with a pumping pressure of 0.4 bar (6 psi) is recommended.
It is important that the pump operates across the entire control range without vibra-
tions, resonance, oscillation or excessive noise. Increased motor noise caused by the
harmonics of the power supply is normal.
During parameterisation of the frequency converter, observe the setting of the quad-
ratic pump curve (U/f curve) for pumps and fans! The U/f curve ensures that the output
voltage at frequencies less than the rated frequency (50 Hz or 60 Hz) is adjusted to the
power requirement of the pump. Newer frequency converters feature an automatic
power optimisation function - this automation achieves the same effect. For the fre-
quency converter setting, refer to its installation and operating instructions.
Faults with the motor monitoring may occur on motors operated with a frequency con-
verter depending on the type used and installation conditions present. The following
measures can help to reduce or avoid these faults:
▪ Keeping within the limit values stated in IEC 60034‑25 for overvoltages and rise speed.
Output filters may need to be installed.
▪ Vary the pulse frequency of the frequency converter.
▪ In the event of a fault on the internal sealing chamber control, use the external double-
rod electrode.
The following construction measures can also help to reduce or prevent faults:
▪ Separate power supply cables for the main and control cable (depending on the motor
size).
▪ When laying, ensure there is adequate clearance between the main and control cable.
▪ Using shielded power supply cables.
Summary
▪ Continuous duty up to rated frequency (50 Hz or 60 Hz), observing the minimum flow
velocity.
▪ Observe additional measures with regard to EMC regulations (choice of frequency con-
verter, using filters, etc.).
▪ Never exceed the rated current or rated speed of the motor.
▪ It must be possible to connect the motor’s own temperature monitoring (bimetallic
strip or PTC sensor).
13.3 Ex rating
This section contains further information on the operation of the pump in an explosive
atmosphere. All personnel must read this section.
This section applies only to Ex-rated
pumps!
13.3.1 Identification of Ex-rated pumps
For use in explosive atmospheres, the pump must be marked as follows on the rating
plate:
▪ “Ex” symbol of the corresponding approval