FUZZBLUE.jpg (23434 bytes)FLOMATCHER/MARATHON

SPECIALISTS IN VARIABLE SPEED MOTOR CONTROL SYSTEMS

Crane

GIANT REVOLVER

The largest revolving shipyard crane on the West Coast was erected in the summer of 1982 at Todd Shipyards in Seattle, Washington. The 150 ton revolver with 210 foot reach was built by Washington Cranes Division of Ederer Incorporated and features static DC controls manufactured by Marathon Electronics. The crane is used to service Todd's 40,000 ton dry-dock and the adjoining deep water berth.

Although the technology to complete this project is dated by today's standards it does show the capabilities of Flomatcher/Marathon in the controls arena. This project could be repeated by Flomatcher/Marathon using current control technology.

Controls for the five-motion crane consist of the main hoist, whip hoist, boom hoist, rotate and gantry. The three hoist motors are 150 HP each with individual controllers. The two 30 HP rotate motors are wired in series and operated by a single controller. The sixteen 7-1/2 HP gantry motors are series-parallel connected and operated by a single controller.

Marathon Electronics supplied the following items for the five-motion crane control system.

Individual thyristor controls for each motion.
Crane control logic panels including:
The complete relay logic for the control of the DC drives as commanded by the operator devices, within safe limits.
Specific safety and coordinating circuits to detect overload, overheat, overspeed, drive and power supply malfunction conditions.
Speed and torque detector circuits which operate an auxiliary brake relay for the release and setting of the brake in conjunction with the motor control.
A high performance current regulator which yields rapid and positive control of the motor.
Motors and brakes for each motion.
Master switches.
Limit switches.

Electrical power for the entire crane is supplied by an on-board Marathon Electric diesel generator rated at 685 HP.

The complete Marathon Electronics system featured the latest in state-of-the-art crane control features and performance. The crane motor controllers are fully regenerative and reversing four quadrant crane duty solid state drives. Each crane motion utilizes one such drive together with coordination and safety circuits. All the crane motions are controlled together by the system master magnetics. Features of the crane control system include:

Torque providing for brake release.
Zero speed detection for brake setting.
Independently adjustable acceleration and deceleration ramps in all four quadrants.
Field loss protection.
Individual armature contactor protection.
Load float.
Extended light hook speed on main hoist.
Circuit checker built in.
Overspeed and drive error protection.
Undervoltage protection.
SCR bridge thermal protection.
Insensitive to incoming phase sequence.
Door interlocked circuit breaker.

CONTROLLER OPERATION

FOUR QUADRANTS OF CONTROL

The motor and control combination are capable of providing controlled torque and speed in four separate speed-torque quadrants. To illustrate further, we will use the hoist motor as the example since it clearly illustrates the four separate conditions that occur.

TORQUE (POSITIVE UP)

II

Brake Reverse

<< Speed (Negative Down) <<

I

Motor Forward

>> Speed (Positive Up) >>

III

Motor Reverse

IV

Brake Forward

TORQUE (NEGATIVE DOWN)

QUADRANT  DESCRIPTIONS

Quadrant No. 1 control occurs when the hook is loaded and it it to move in the up direction. Under this condition it takes up torque to lift the load. The hook in this mode of control will then move up under positive torque.

Quadrant No. 2 mode of control will occur when the hook is still fully loaded and the command is to move  in the down direction. If the brakes were released, the hook would free fall in the down direction. For this reason, if we are to control it in the down direction, we must produce a torque in the up direction but allow the motor to move in the down direction. This is a braking mode of control and the control system must be capable of absorbing energy , and pumping it back into the power system.

Quadrant No. 3 control occur when we are driving down in the down direction. This is the case of an empty hook which is to move in the down direction. We must first motor down to accelerate the drum and hook to the required speed and then provide just enough down torque to overcome gearbox friction.

Quadrant No. 4 control occurs where we are moving in the up direction but torque is in the negative direction of braking. Thus, this is a braking mode of control and energy must be absorbed in the control system as was the case in Quadrant No. 2 control. This is when we are moving up with an empty hook and are trying to reduce speed by absorbing the inertial energy of the drum and gearbox. We must apply downward torque to slow its speed in the up direction.

SAFETY MODULE

The safety module ensures that drive operating conditions are normal. the safety module monitors drive error, overspeed, field loss and power supply loss. Should any of these inputs indicate a safety condition error, the safety module will de-energize causing the drive to shut off.

LIGHT HOOK SPEED

Light hook speed of 217% base speed on the main hoist is accomplished with our field regulator module. This module permits extended motor speed range operation over that normally attained by armature control alone. This is accomplished by controlling the field current to the motor. As the field current is weakened, the motor speed increases. Under load the field current is strengthened to provide torque capability for hoisting.

LOAD FLOAT

Precise control at slow speeds is enhanced by utilization of the load float feature. By depressing the load float pushbutton, a scaling resistor is inserted in the path of speed reference. This resistor limits the amount of reference to the drive, permitting precise control.

MAINTENANCE

Troubleshooting is made easier and downtime is minimized through the use of a built-in circuit checker on the drive regulator card and removable programming cards on the crane control module and the field regulator module. The circuit checker consists of a meter and selector switch and monitors twelve critical circuit points. The removable programming cards permit replacement of the crane control module or the field regulator module without the need of adjusting the new modules to the drive system.

PRINCIPLE CRANE DATA

LIFTING CAPACITY

Main Hook: 150 tons at 55 ft. radius.; 50 tons at 120 ft. radius.

Auxiliary Hook: 15 tons at all radii from 61 ft to 210 ft.

DIMENSIONS:

Boom Length: 200 ft. from Hinge Pin to Tip.

Gantry Height: 110 ft from Ground to Boom Hinge Pin.

Rail Circle: 30 ft. Diameter.

Track Gage: 32 ft.

Tail Swing: 28 ft. radius (rotation of upperworks)

SPEEDS

Main Hook: 12 ft. per minute.

Auxiliary Hook: 100 ft. per minute.

Boom: 3 minutes from fully lowered to fully elevated.

Rotation of Upperworks: 1 Revolution per minute.

Crane Travel: 150 ft. per minute.

WEIGHTS

Operating Crane Weight: 647 tons including 200 tons of counterweight.

TOTAL HEIGHT

With the boom fully elevated the crane is 314 feet tall and is taller than any other crane on the Seattle Waterfront.

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Last modified: June 11, 1998