EMA service engineers spend a lot of time working in mines and quarries maintaining Medium Voltage Variable Frequency Drives. Many of these mines and quarries feed associated plants that are used for further refinement, but getting the raw material to the plants from the mines poses a challenge. The two most common ways used are trucks and conveyer systems, and conveyors tend to be the most economical option.
When conveyors are used, there are often electric motors that are powered by Medium Voltage VFDs running in coordination. The distance of the conveyor (we’ve seen conveyors over 5 miles long!) determines how many motors and drives are used.
Coordinated drive systems like this can be tricky to set up and troubleshoot. There is typically a “master” VFD and all other VFDs are “followers” of the master. A proper setup reduces the push and pull effect on the motors and prevents overload or over current faults on the VFDs and allows the load to be shared equally without one motor taking the brunt of the load.
Recently we were involved in remotely troubleshooting a coordinated system on a long conveyor line at a cement plant. Troubleshooting a coordinated Medium Voltage Drive system in person is challenging enough, so phone support is particularly tough!
In this case, there were three Toshiba T300MVi Medium Voltage Drives on a master/follower conveyor system and the VFDs were experiencing intermittent over current (IOC) and overload faults. After a review of the traceback files given to us from the customer, we suspected the problem could be multiple things: a speed mismatch, oscillation/tuning issues, mechanical issues on the pulleys/gear box, or elasticity of the conveyor belt itself.
Unfortunately, without additional information, it was virtually impossible to determine the root cause of their issue remotely, and due to budget constraints, the customer couldn’t afford a service call.
Our DriveScan remote monitoring tool would have proven extremely valuable in this situation. Had DriveScan been installed on those three drives, we could have seen the speed of all three VFDs in real time, allowing us to easily see if speed mismatch was the problem. The constantly trending historical data would also have shown us if anything has changed over time, indicating a possible problem.
DriveScan would have also allowed us to help the customer tune the speed loop gains on the fly to tune out possible mechanical issues due to worn belts or pulleys. By looking at real-time data on the VFDs via the DriveScan dashboard, we would have had access to all the critical data needed to help the customer tune their drives. In coordinated drive systems, output voltage, output frequency, and output current are all important readings to have in order to make sure the drives are properly synchronized to prevent oscillation.
In the screenshot below, we’re comparing the output voltage and current of two medium voltage VFDs at two separate locations at the same time. This functionality is invaluable for remote troubleshooting as well as root cause analysis and predictive failure.
Do you have Medium Voltage Drives running in coordination? Or do you have critical Medium Voltage Drives that can’t afford to be down? Let EMA and DriveScan help you! We deal with this stuff every day and we’re the best in the business. Call Us, Email Us, or use the chat function on our website to speak with someone today!
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