In order to ensure the normal start of the crane, the rotor of the motor must be connected with additional resistance, so as to limit the average starting current of the crane to no more than two times the rated working current.
And this task is usually done through resistors, cranes are commonly used in the open and protective type of two different types of resistors.
In the actual application of installation, they can be stacked in each other in the motor of the crane, once more than four boxes should be placed on the special metal frame, and adjacent to the two groups of resistors should be 80mm between the interval, the middle can be installed heat insulation board.
It is important to note that the open resistor should be installed with a shield to prevent staff from accidentally touching the resistor live body, grounding screws must be reliable grounding.
When selecting resistors for cranes, it is necessary to consider the motor model, power, power continuity, controller model and other parameters, and require them to match;
At the same time, when wiring, the bridge should be used to detect the resistance and total resistance value of each section, and the specified numerical error range should be within 15% plus or minus, and according to the manufacturer's resistance value distribution table data on the correct connection.
Two motors for supporting agencies or double car crane with the resistor should be chosen by the same manufacturer, same type of products, to make the paragraphs resistance is close to, should be avoided due to connect to the resistor wire length and motor rotor resistance is poor, brought by the internal resistance value is different to ensure the mechanical properties of two driving motors.
In the process of crane operation, the resistor should be observed at any time whether there is overheating phenomenon, the temperature of each section of resistance is higher than the ambient temperature.
If the resistor breaks, it can be shorted in case of emergency use.
Wait until the work is finished to replace in time.