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7.6
Monitoring the direction of rotation
The direction of rotation must match the
direction arrow on the motor, i.e. clockwise
when looking from above (fig. on right)
To perform this check, ensure
that the pumps have a safety
clearance (at least 1 metre)
from persons, animals, and
objects.
7.7
For small pumps
To check the direction of rotation, slightly lift the pump and briefly switch the motor on and
immediately off again. If the direction of rotation is correct, the pump pushes back in a coun-
ter-clockwise direction. The direction of rotation can be changed by disconnecting, swapping
and then reconnecting two phases. For larger pumps or pumps that are already installed, the
inspection of the correct direction of rotation is performed by comparing the pump height and
the pumped quantity in different directions of rotation. The direction with the greatest pump
height and pumped quantity is the correct direction of rotation. If the direction of rotation is
incorrect, disconnect, swap and then reconnect two phases of the mains connection.
7.8
Operation with frequency inverter (FI)
Most drainage water/sewage pumps can be operated with frequency inverters (see "Techni-
cal Data") if the following guidelines are adhered to. Experience shows that it is advisable to
over-dimension the frequency inverter by one size. This enables reliable compliance with the
following requirements.
–
The rated current must not be exceeded at the rated voltage and rated frequency.
–
The operating frequency is between 25 Hz and a rated frequency of 50 Hz
–
The ramp-up time from 0 Hz to 25 Hz or vice-versa must be a maximum of 1.5 seconds
–
The voltage rise – voltage peaks (dV/dt) should be below 750 V/1 sec
–
A suitable sinus filter must be used (note the FI manufacturer specifications).
–
For the PWM inverter, a carrier frequency at the lower end of the selection range should
be selected.
–
The thermal load in the motor must be calculated and monitored by the FI (ETR – Elec-
tronic Thermal Relay) so that this does not overheat.
Direction of rotation
Rash
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