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10. APPENDIX
APPENDIX A
GENERAL RECOMANDATIONS FOR THE APPLICATION OF SUBMERSIBLE MOTORS WITH VFD (INVERTER)
MOTOR CONFIGURATION
•
Rewindable waterfilled motors (MS series): only the motors with the PE+PA winding are suitable for the application under in-
verter
•
Oil filled motors (CL series): all the threephase motors in the standard version are suitable for the application under in-
verter
LIMIITS OF THE APPLICATION FREQUENCY
•
Max frequency: the maximal working frequency should never exceed the nominal frequency of the motor.
•
Minimal frequency: the minimal frequency should be calculated in the way to guarantee always the necessary motor cooling.
The water
speed to be guaranteed depends on the its temperature and on the motor power but in all the cases it can be
never lower than 0,1 m/s. In all the cases the application of the motor at the frequency lower than 30 Hz can cause seri-
ous damages.
SPECIFIC FUNCTIONS FOR THE PUMPS
•
If the inverter has functions or macro specifications for the pumps (for example macro PFC), make them operative. Enable
also features to limit overvoltages (e.g. Surge limit etc..)
START
•
Starting ramp: The ramp should last approximately 4 – 6 seconds (from the starting to reaching the minimal application fre-
quency 30Hz) to avoid damage to plant and / or motor.
•
If available, make operative the function of torque boost.
•
Number of starts per hour: respect the number of starts/ hour indicated in the technical documentation of the motor.
FREQUENCY VARIATIONS IN A MINUTE
•
Max number of the frequency variations in a minute= 8
STOP
•
The stop can be effected in two ways:
•
Taking off the power source from the motor and making the motor stop by inertia. This mode of making stop the motor safe-
guards the motor but can cause the appearance of the water hammers, depending on the characteristics of the plant.
•
Setting up a stopping ramp: in this case are valid the indication already given for the starting ramp.
SWITCHING FREQUENCY
•
It is suggested to set up the switching frequency on the values between 3 and 5 kHz.
FILTERS
•
Filters and cable length: applications with submersible motors can cause stress on the windings and the motor insulation sys-
tem, at shorter distances than for applications where the motor cables are in the air. Therefore, the tables with the maximum
permissible cable lengths that are usually found in the VFD documentation are not valid for applications with submersible mo-
tors.
•
Sine wave du / dt filter: du / dt filters limit output voltage peaks and thus make motor life longer. Their application is neces-
sary depending on the inverter (brand and type), cable length, motor power supply voltage, and other factors. Refer to the
table below. These filters also limit the capacitive dispersion currents and the high frequency emissions of the motor cables.
Filters must be sine wave type. Traditional du / dt filters are not effective in the protection of the submersible motors. Please
consult the inverter supplier for more information.
Motor
CL95, CL140
6" MS<30kW
6 " - 8 " - 1 0 " - 1 2 "
MS
POSITION OF THE PRESSURE TRANSDUCER
•
If the inverter is connected to a pressure transducer, the position of the transducer should make possible to assure the correct
interpretation. Don't install the transducer next to the curves, connections or in areas where it can create turbulence or forma-
tion of air.
42
Cable length ≤ 20 m
Insula-
Filter
tion
standard
None
PE + PA
None
PE + PA
Sine wave
filter
Keep the manual for future reference - For more informations visit www.saerelettropompe.com
Upeak
Max.dU
Insulation
max
/ dt
850 V
2000 V/µs
standard Sine wave filter
850 V
500 V/µs
PE +PA Sine wave filter
850 V
500 V/µs
PE +PA
- Translation of the original instructions
Cable length > 20 m
Filter
Upeak
max
850 V
850 V
850 V
Sine wave filter
Max.dU / dt
2000 V/µs
500 V/µs
500 V/µs
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