PLC Troubleshooting Made Easy

The average time to locate a blown fuse, tripped overload, tripped breaker, power supply problem, or drive fault is about two minutes from seeing the fault to having the suspect part identified. When Casa Herrera approached control system integrator MEMCO - we wanted a control system that had a cutting edge intuitive diagnostic system, got around language barriers, and was able to implement remote servicing capabilities over the Internet.

The average time to locate a blown fuse, tripped overload, tripped breaker, power supply problem, or drive fault is about two minutes from seeing the fault to having the suspect part identified.

When Casa Herrera approached control system integrator MEMCO - we wanted a control system that had a cutting edge intuitive diagnostic system, got around language barriers, and was able to implement remote servicing capabilities over the Internet.

Because virtually all control system information is stored in the PAC’s CPU, the troubleshooting system could be very elaborate. We chose to use high resolution photographs of the panel back plate as-built drawings, showing every component in its relative position.  

We then used popup windows to overlay the panel drawings in their location on the machine.

These pop up windows become visible when any fault occurs, and an animated red box blinks around the problematic item.

The PAC 3000 processor keeps track of the status of system components, and assigns conditions to tag names when we add a module or component.

For example, in the tag name database for an 8-channel output card, there is a module fault tag as well as a tag indicating a blown fuse on each of the outputs.

We can use this information to bring up a button on the display screen that blinks and informs the operator that there is a module problem.

When the operator presses the button, it takes him to a high resolution photograph of the machine and of the panel where the blown fuse is located. When the operator touches the picture of the panel, another high resolution image of the back plate inside the panel appears in front of the enclosure image.

On the image of the back plate, a red blinking box appears around the suspect module. Another high resolution image of the component side of the output card appears next to the chassis.

The top image shows the location of the fuse circled in a red blinking box - and the function, type, rating, and part number of the replacement fuse in a text window.

The PAC 3000 system allows hot swapping of modules, so the maintenance person can check the circuit and repair the short. He or she can then pull the card out hot, replace the fuse, reinsert the card, and restart the machine.

The average time to locate a blown fuse, tripped overload, tripped breaker, power supply problem, or drive fault is about two minutes from seeing the fault to having the suspect part identified.

Troubleshooting the motor drives is just as easy. When a drive fault occurs, the same sequence of windows and animation leads the maintenance person to the correct panel. A blinking box depicts the tripped drive, and a text window tells what equipment the drive operates.

The box also shows what type of fault has occurred such as an over current during running, a ground fault at the motor, a phase loss, or some other abnormal condition.

One of the most unique features of the control system is the transfer of motor drive information. If a customer has a faulty motor drive - the repair procedure is to turn off the power, unplug the communication cable, install the new drive, plug in the communication cable, and power up the drive.

Because all motor drive parameters are stored in the PAC’s CPU, upon first scan the processor recognizes the new drive. The PAC then reconfigures the communication port for remote control and downloads all drive parameter settings, all in about 3 seconds. This means that local plant personnel don’t have to be familiar with motor drive or control systems programming to replace a drive.

The troubleshooting system usually enables quick repair to be performed by a mid-level maintenance person. But if the problem cannot be solved quickly on site, the PAC and the HMI feature full remote access.

With this feature - every I/O module, motor drive, and sub component connected to any of the communication ports can be accessed thru the Ethernet data port – either locally or remotely through a standard Internet connection.

We can remotely view every motor drive parameter as well as every status register. The same goes for every rack, power supply, and I/O module. The HMI screens also allow live real-time remote viewing and control so the screen faults can be seen from anywhere. For detailed off-line analysis - the data logs, fault logs, and event logs stored on the local USB memory stick can be viewed and downloaded using FTP.

Since the commissioning of the first PAC 3000 tortilla line for True Foods in Melbourne, Australia - we have gone online from California to monitor the control system in real time. 

We have added customer specific changes to the PAC program, and we’ve tuned motor drive parameters. We also added new screen buttons and data trending features to the HMI, all in a matter of minutes. 

For more information, visit www.memcoautomation.com, www.quantumautomation.com, www.casaherrera.com, and www.automationdirect.com.

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