Magnetek, Inc.

Aaron S Kureck

Kurtis L Verheyen

Eric L Schlevensky

A system and method for determining the load in a material handling system is disclosed. The load weight detection system measures torque at four operating conditions both at constant speed and during acceleration. The level of torque generated by the motor under each of these operating conditions is stored in the motor drive. The motor drive also receives a signal corresponding to the speed of the hoist motor. Based on the measured torque, as well as the expected torque at no load and at rated load for the measured speed, the motor drive then determines the load present on the hoist. In some systems, two or more hoists are required to operate in tandem to lift a load. Each motor drive determines the weight of the load supported by its respective hoist motor and determines a total weight of the load based on the weights determined by each motor drive.

System and method for determining a load in a material handling system

A system and method for determining the holding torque of a brake in a material handling system is disclosed. The material handling system may include a bridge, a trolley, and a hoist, each driven along a different axis by a motor. A brake is operatively coupled to the motor to prevent unwanted motion of the motor. A motor controller is coupled to each motor which controls operation of the motor and its corresponding brake. The motor controller generates a torque command to the motor while keeping the brake set. The initial torque command is less than the holding torque of the brake. The torque command is incremented until motion is detected on the motor. The torque value when motion is detected is stored in the motor controller and displayed to an operator.

Method and apparatus for calibrating and testing brake holding torque

A variable speed power converter controls the speed of a load in a material handling system as a function of the torque required to move the load. While the power converter is running, the torque being produced in the motor is determined. The power converter then determines the maximum rotational speed of the motor as a function of the torque currently being produced and of the torque-speed curve of the motor. The power converter then commands the motor to rotate at this maximum rotational speed. The power converter periodically monitors the torque being produced and adjusts the maximum rotational speed of the motor throughout the run.

Method and apparatus for load dependent speed control of a motor

An electronic limit switch software module is programmed into a controller for a hoist system. The electronic limit switch determines the rotations of a motor to keep track of the location of the load. Arbitrary stop and slow down locations may be input into the system so that the system can determine when to stop and slow down the load.

Hoist system with an electronic programmable limit switch

Two incremental shaft encoders are mounted on the two extreme ends of a mechanical drive train. The encoders generate data which is representative of the rotational speed of the drive train component proximate to where the encoder is mounted. The data from the encoders is communicated to a logic unit associated with operation of the drive train, such as a variable frequency motor drive (VFD). Software in the logic unit monitors and compares the speed of both encoders. An encoder resolution setting and a gear ratio are entered into the software parameters. If a difference in speeds (as monitored and indicated by the encoders) is greater than a preset value for a period longer than a preset time period, the logic unit displays an error message and a programmed action (such as motor shutdown and load braking) is executed.

System and method for detecting a discontinuity in a mechanical drive train

Included herein is a system and method for controlling a velocity vector of an overhead crane. A motor is attached to the crane and is positioned to move the overhead crane and has an output vector including a rotational direction and a rotational speed. A variable frequency drive is positioned to transfer voltage and current at a frequency to the motor. A processing unit converts the output vector to an amount of voltage and current at a given frequency and can instruct the variable frequency drive to send a frequency to the motor at a frequency substantially equal to the frequency at which the motor is presently rotating. This creates a speed match for the motor reducing spikes during operation of the motor and substantially eliminates open circuit decay. A hydraulic brake operates in connection with the processing unit and the variable frequency drive to slow the crane without driving the motor into the brake.

Control system and method for an overhead bridge crane

A hoist synchronization apparatus and method using a master controller operating software that provides a pulse reference to a slave controller. The slave commands its motor to rotate at the speed conveyed by that pulse reference. The slave controller monitors the pulse feedback from both the master encoder and the slave's encoder and compensates for any position error by adjusting its motor output speed. In addition, the slave controller includes the capability to automatically resynchronize the hoists. Resynchronization is accomplished by storing position error generated when either the master or the slave is run independently and correcting for the error when both units are operated at a later time.

Multiple hoist synchronization apparatus and method

A dual hoist bucket crane controller for operating a closing motor and a holding motor using a close inverter adapted to control the closing motor and a hold inverter adapted to control the holding motor where the hold inverter and the close inverter are internally controlled and operate independently from the other drive. Also covered is a dual hoist bucket crane controller for operating a closing motor and a holding motor using a dual axis master switch adapted to provide a close inverter input signal to the close inverter and a hold inverter input signal to the hold inverter.

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Oconomowoc, WI, United States of America

Aaron S Kureck