QT-60-80 tower crane main circuit

Tower crane is a kind of track-mounted lifting machinery commonly used on construction sites . It includes four parts: traveling mechanism, slewing
mechanism, luffing mechanism and lifting mechanism, which
are driven by JZR2 series winding asynchronous motors respectively. The main circuit and control circuit of the QT-60/80 tower crane are shown in Figure 8-10 and Figure 8-11 respectively. The lifting motor
Mi has speed regulation requirements, and its rotor circuit uses external resistance. The luffing, slewing and traveling mechanisms do not have speed regulation requirements, so
the corresponding motors are started with frequency-sensitive rheostat to limit the starting current and increase the starting torque. After starting,
short-circuit the frequency-sensitive rheostat.
    On the stator circuit of the variable mantle motor Ms, an electromagnetic brake YAs is connected in parallel. The brake wheel
is coaxial with the motor Ms. Once Ms and YAs are powered off at the same time, emergency braking can be performed to accurately stop the boom at a certain position.
    An electromagnetic brake YA4 is connected in parallel to the main circuit of the slewing motor M4, which is used to control the slewing locking braking mechanism
. In order to ensure that the heavy objects on the hook can be accurately placed at the predetermined position even in windy conditions,
a locking braking mechanism is installed on the other end of the motor M4 shaft. When the electromagnetic brake is energized, the locking braking mechanism is driven. The rotating mechanism locks the rotating
mechanism so that it cannot rotate and is fixed in a certain position. In the picture, 51sQ and 52SQ are the limit switches
    of the boom pitch amplitude , 21SQ and 22so are the front and rear limit travel switches of the traveling mechanism motors Mz and M3 to prevent derailment accidents, iiso, 12SQ and 13so are the super-height and wire rope detachment switches of the crane respectively. Limit switch for tank and overweight protection .