KSB UPA Installation & Operating Manual page 43

5 Installation at Site
If KSB's submersible borehole pumps are operated on a frequency inverter, the
pumps' special design (low moment of inertia, high output per size, etc.) requires
that the following points be observed.
Power reserve of the submersible motor
If supplied by KSB for operation on a frequency inverter (see data sheet), the motor
comes with a 5 % power reserve.
To check whether a frequency inverter can be retrofitted, contact the pump
manufacturer.
Power reserve of the drive
Apart from the dimensioning factors for the submersible motor, additional voltage
losses in power cables, filters, inverter, etc. must be taken into account as they can
lead to the required current input exceeding the nominal motor current. A reserve
for the frequency inverter / system must be provided for this purpose. In addition, for
UMA-S 150, UMA-S 200 and UMA-S 250 motors, the nominal motor current depends
on the type and quality of the frequency inverter's control process. Sub-optimal
motor control can lead to a higher motor current, which can have a negative impact
on the efficiency, for example. This must be considered when selecting the system. A
reserve of 10 % of the nominal motor current is recommended. For any queries,
contact the manufacturer of the frequency inverter.
Control principle of the frequency inverter
▪ For asynchronous motors, the control principle must correspond with a linear V/f
characteristic.
▪ For synchronous motors, frequency inverters are used that have a sensorless
control principle suitable for motors with interior magnets.
If any other control principles are employed, such as field-oriented frequency
inverters or frequency inverters with DTC or NFO, the manufacturer of the frequency
inverter must ensure that the particular characteristics of submersible motors (very
small moment of inertia, electrical data) are taken into account.
Maximum permissible run-up time and run-down time
The run-up time from standstill to the minimum frequency f
2 seconds. The run-down time must also be limited to a maximum of 2 seconds.
Minimum frequency
Make sure the following minimum frequencies are met.
Table 17: Minimum frequencies [Hz]
Motor size
DN 100
UMA 150
UMA-S 150
UMA 200
UMA-S 200
UMA 250
UMA-S 250
UMA 300 - 2 poles
UMA 300 - 4 poles
14D - 2 poles
14D - 4 poles
UPA / UPA S
Minimum frequency f
For vertical installation
30
20
40
20
40
20
40
20
30
20
30
must not exceed
min
min
For horizontal installation
30
30
60
30
60
30
60
30
35
30
35
43 of 98