Nastec MIDA 203, Руководство по установке, использованию и техническому обслуживанию

Страница: 52 / 56

NOTE
With three-phase asynchronous motors, the correct value to which parameter Dry run cosphi is to be
set depends on:
• The type of motor (construction and winding data). Generally, three-phase surface motors have a
higher rated cosphi than submersible motors having the same power rating.
• The type of pump (hydraulic performance and power consumption curve).
• The power supply characteristics (voltage and frequency).
In general, the parameter Dry run cosphi may be set to 60% of the nominal cosphi shown on the
pump's data plate.
Parameter Dry run cosphi must also be determined empirically at the end of the installation. In the
presence of centrifugal pumps with three-phase asynchronous motor, a simple method consists in
starting the pump at the rated frequency and, paying attention to the sustainability of the system,
completely closing the delivery and then reading the measured cosphi value on the display (or on the
App). Parameter Dry run cosphi must therefore be set to 10% less than the cosphi value read under
closed flow condition.
CAUTION
The electronic water shortage protection based on parameter Dry run cosphi works correctly only
with centrifugal pumps equipped with three-phase asynchronous motors.
In the presence of permanent magnet motors it is not possible to base the water shortage protection
on the cosphi reading; it must be based on the absorbed power, instead.
When parameter Motor type is set to Synchronous PM, parameter Dry run cosphi takes on the
meaning of a percentage of the absorbed power.
In the presence of other types of pumps and motors, it is advisable to contact the technical support
service.
WARNING
If parameter Dry run cosphi is set too low, the electronic water shortage protection may no longer be
effective.
Typically, it is recommended not to go below the value of 0.5 with centrifugal surface pumps and 0.4
with centrifugal submersible pumps equipped with asynchronous three-phase motor.
Setting parameter Dry run cosphi to 0 completely excludes the water shortage protection.
MIDA
52