Installation and maintenance of resistors for cranes

When the crane motor is started, the rotor must be connected in series with an additional resistor to limit the average value of the starting current to no more than twice the rated current of each work. JZR and YZR series resistors are commonly used. They are divided into open type and protective type. They can be stacked on each other during installation. When there are more than four boxes, they must be placed on a special metal rack. There should be an 80mm interval between two adjacent groups of resistors, and a heat insulation board can be installed in the middle. When installing the open resistor, a fence should be added to prevent the staff from accidentally touching the live body of the resistor. The grounding screw must be reliably grounded.

The selected resistor should match the motor model, power, power-on duration, controller model and other parameters. When wiring, a bridge should be used to detect the resistance of each section and the total resistance value. The error range with the specified value should be within ±15%, and the resistor should be correctly connected according to the data on the resistor value distribution table provided by the manufacturer. The resistors used for the two motors of the trolley running mechanism or the double trolley crane should be products of the same manufacturer and the same model to make the resistance values ​​of each section close. The resistance difference caused by the different lengths of the wires connected to the resistors and the resistance values ​​of the motor rotors should be avoided to ensure the consistency of the mechanical characteristics of the two drive motors.

Regularly remove dust and metal oxides from resistor elements to facilitate heat dissipation. Regularly check whether the components are broken or short-circuited, whether the insulating porcelain parts are damaged, whether the fastening screws are loose, and regularly measure the insulation resistance of the resistor to ground. The resistance value should be above 0.5MΩ.

During operation, observe whether the resistor is overheated at any time. When the temperature of each resistor section is higher than the ambient temperature by 350℃, consider increasing the capacity of the resistor. When it is lower than 100℃, it means that the resistor capacity is sufficient.

If a resistor breaks, the broken section can be short-circuited for emergency use and replaced promptly after the work is completed.

Resistors with broken soldering should be soldered with hard solder such as brass, silver or copper phosphorus.

If two motors of the same model are driven at the same time (such as trolley motors), and the rotor winding resistance of one of them is reduced after the rotor winding is rewound, a set of resistance elements can be installed in the empty space in the resistance box and connected in series between the resistor and the motor rotor circuit to make the rotor winding resistance of the two motors consistent. The installation method is shown in the figure.