Over Head Crane Motor Control Circuit - Electrical Machines
head cranes are used for shifting heavy weights
limited area. The area is decided by the span of long travel motion and cross travel motion of the crane. Weight in the defined area are picked up and shiftesta tony desired position with the help of three motions.
1. Hoisting, lowering
2. Longtravel (ie. Forward, Reverse)
3. Cross travel (which is ir to long travel)
An overhead crane has to handle heavy weights in terms of thousands of kgs requiring high starting torques in all the motions. So we use slip ring induction motor for all.
motor The crane moves on the rails for long travel driven by slipning induction motor known as long travel (LT) motor. This motor is installed on the structure itself. On the structure itself rails are mounted for cross travel (CT) trolley: The CT trolley moves on these rails by a CT motor mounted on the trolley itself.
The hoisting motor is also installed on the trolley. Hoisting is done by a rope wound on the drum attached to the motor shaft. A hook hangs at the bottom of the rope which is engaged with the weight to be lifted.
The operation of crane is done from a cabin on the crane, which is situated on the lower side of the crane, in such a way as to allow clear visibility of the shop floor to the travel, cross travel and hoist are provided. operation In the cabin there are three master controllers for long travel.
Master controller:
The drum switch is called master co master controller has three or four steps on 1, 2 and of the master controller in one direc speeds of the motor in one direction. BY in the other direction the motor can direction, at three different speeds. An important interlocking arrangem control is that the control can be switched the master controllers are in the neutral
master controller. The steps on each side. Steps in one direction gives three Election. By moving the handle motor can run in the reverse.
interlocking arrangement made in crane
control can be switched ON only when all
are in the neutral or OFF position. motion of the crane either in long travel or in Cross
avel and hoist can be restricted by six control limit switches, two for each type of motion are provided. Supply to the crane is given through overhead bus bars known as down shop leads (DSL). Current is collected from the bus bars by current collectors which is slide on the bus bars.
For simplicity we are going to discuss about the control circuit of hoist only. Because connections for LT and CT motors are basically forward and reverse starter except for the hoist motor in which an extra contactor is used for single phasing of the motor for a few seconds during lowering operation. Hence the break does not open fully sudden jerk is avoided. Control circuit operation
In the control circuit start relay 'S' gets energised an remains held only when the "O" contacts of all the thre master controllers (Hoist, LT and CT) are in closed positiv ie., levers are in OFF position.
limited area. The area is decided by the span of long travel motion and cross travel motion of the crane. Weight in the defined area are picked up and shiftesta tony desired position with the help of three motions.
1. Hoisting, lowering
2. Longtravel (ie. Forward, Reverse)
3. Cross travel (which is ir to long travel)
An overhead crane has to handle heavy weights in terms of thousands of kgs requiring high starting torques in all the motions. So we use slip ring induction motor for all.
motor The crane moves on the rails for long travel driven by slipning induction motor known as long travel (LT) motor. This motor is installed on the structure itself. On the structure itself rails are mounted for cross travel (CT) trolley: The CT trolley moves on these rails by a CT motor mounted on the trolley itself.
The hoisting motor is also installed on the trolley. Hoisting is done by a rope wound on the drum attached to the motor shaft. A hook hangs at the bottom of the rope which is engaged with the weight to be lifted.
The operation of crane is done from a cabin on the crane, which is situated on the lower side of the crane, in such a way as to allow clear visibility of the shop floor to the travel, cross travel and hoist are provided. operation In the cabin there are three master controllers for long travel.
Master controller:
The drum switch is called master co master controller has three or four steps on 1, 2 and of the master controller in one direc speeds of the motor in one direction. BY in the other direction the motor can direction, at three different speeds. An important interlocking arrangem control is that the control can be switched the master controllers are in the neutral
master controller. The steps on each side. Steps in one direction gives three Election. By moving the handle motor can run in the reverse.
interlocking arrangement made in crane
control can be switched ON only when all
are in the neutral or OFF position. motion of the crane either in long travel or in Cross
avel and hoist can be restricted by six control limit switches, two for each type of motion are provided. Supply to the crane is given through overhead bus bars known as down shop leads (DSL). Current is collected from the bus bars by current collectors which is slide on the bus bars.
For simplicity we are going to discuss about the control circuit of hoist only. Because connections for LT and CT motors are basically forward and reverse starter except for the hoist motor in which an extra contactor is used for single phasing of the motor for a few seconds during lowering operation. Hence the break does not open fully sudden jerk is avoided. Control circuit operation
In the control circuit start relay 'S' gets energised an remains held only when the "O" contacts of all the thre master controllers (Hoist, LT and CT) are in closed positiv ie., levers are in OFF position.
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