Wegner Crane CFW500 series, Руководство по применению

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Introduction to the Crane
Crane | 16
Being:
P
Resistor
= braking resistor power (kW);
P
Load
= power required by the load (kW).
%ED = braking duty cycle.
NOTE!
Refer to the CFW500 user's guide, table B.1, to verify the ohmic value of the braking resistor to be
used according to the frequency inverter model.
NOTE!
If the power required by the load is unknown use the motor rated power considering the service fact
to the dimensioning of the braking resistor.
1.5.3 General Notes
■
The braking resistor selection can be optimized if the customer provides the power calculated for the load
hoisting or for its horizontal motion. E.g., supposing that the power calculated for the hoisting of an overhead
crane is 17 kW, the used motor would be a 20 kW (commercial value). In this case, the braking resistor can be
obtained from the calculated power, in other words, 0.7 x 17 = 43.4 kW;
■
The installation condition, vibration and protection degree must be observed for the braking resistor
specification;
■
For the replacement of slip ring motors by standard motors, use a minimum factor of 1.2. The inverter
selection criteria remain the same, adopting the current of the new motor. Another criterion that can be adopted
is to use a motor whose frame is the same of the slip ring motor, provided that the ratio between the power of
the new motor and the old one is close to 1.2. The slip ring motors used in cranes usually have bigger frame
sizes than the same power range standard motors. The main advantage of adopting this criterion is the easy
mechanical adaptation of the new motor.