NEWS AND NOTES FROM DELTA AUTOMATION, INC.
News and Tech Tips on Programmable Controllers, Drives and Peripheral Hardware Support.
Delta received a call mid-afternoon last Friday with an emergency need for six obsolete, Modicon B246 output modules. Our stock was checked and there were plenty of these units in stock. However, these units have a very high failure rate component in them, so each unit would need to be properly tested before we could ship them overnight to the client. The latest that we could have them ready to ship was 6:00. It was already 3:00. As luck would have every unit had at least one of these components bad. A quick triage was performed to determine which units could be repaired the quickest. We informed the client that all of these units needed repair. The client said that they could live with just 4 units overnight and the remaining two on Monday. Our repair technicians went to work. They repaired and tested four of the units. They were packed up and shipped in time. The client received the units early the next morning and they kept his equipment in production. This is the type of service that Deltas’ clients have come to depend upon when they need it most!
In late July, Delta Automation hosted an industrial Drives and Controls Rolling Roadshow. It is a great show piece presenting the industries newest drive products. Although primarily focused on AC drives, it also featured a DC drive as well. The onboard demonstrations were the true stars of the show, particularly the Ultra-Low Harmonic Drive setup, comparing a drive only, a drive with a line/load reactor, a drive with an active (dV/dT) filter to the ULH drive. The results were demonstrated visually, real-time, on a harmonic disturbance analyzer.
Customers were able to walk through the truck speaking with the representatives and interacting with the demos at will. Lunch was provided and we were pleased to have such a great customer response to the event. The weather was hot and humid, but thankfully the storms held off throughout the show.
Last weeks multiple massive thunderstorms caused major power dips, voltage spikes/surges, voltage fluctuations, phase losses and generator switch-overs. All of these electrical events can create havoc upon sensitive electronic devices. VFDs are no exception.
During these storms with all of the electrical activity occurring, 4 separate, critical VFDs running air handling systems throughout the hospital unit failed. Clean, filtered air flow is a necessity in these locations. Delta was called to evaluate these failed units on an emergency basis. The hope was that Delta could quickly repair these VFDs. Unfortunately, all 4 of the units were damaged beyond any economical repair. Delta immediately provided 4 new replacement VFDs and had them all retrofitted into the old VFD panels, up and running, overnight.
This is a good article from the U.S Department of Energy discussing the effects of VFDs on non-inverter duty rated motors. It discusses the insulation class recommended, in this article, “class H” is suggested. I previously had been recommending at a minimum, “class F” motor insulation. The article further discusses the use of load reactors and dV/dt filters to reduce the damaging effects upon motors, and mentions that these issues are especially high when running multiple motors on one VFD.
Typically when clients ask about running non-inverter duty rated motors with a VFD, they want to know if the motor will fail. The answer is: eventually. I inquire about the criticality of the application. Is this an application that demands constant up-time? If so, then it is wise to replace the motor when installing the VFD. Some VFD/motor manufacturers will extend their warranty if both are replaced simultaneously. If the application lends itself to some down-time, such as a multiple pump application, then run the motor until it fails, to maximize its’ initial ROI. This may be weeks, months or years later, but it will eventually fail. However, the best practice is still to be certain that the motor is rated for inverter duty to insure the longest lifespan. As the above article states, a work-around to this dilemma, rather than replacing the motor, is to install a load reactor or dV/dt filter between the VFD and the motor(s). Especially if there are multiple motors and/or the motor leads (commonly called “T” leads) are longer than about 100 feet. In these two particular applications (multiple motors or long leads), a reactor or filter is a good practice even when the motors are rated as inverter duty. Different VFD manufacturers recommend different maximum cable lengths before requiring reactors or filters. Check with the manufacturers recommendations to be certain.
Students and faculty from ECPI’s Megatronics program visited Delta Automation to get a view of what opportunities may exist in the field after graduation.
Graphic courtesy of NOAA
Delta Automation is prepared to assist any or all of our clients that were in the path of Harvey or may be in the path of Irma. Our stock of new and refurbished equipment is ready to go to get you or your clients equipment up and running as soon as possible.
Our field service team will be on alert to assist with any on-site needs as well. Please don’t hesitate to contact us via phone or email!
804 236 2800 or 1 888 PC DELTA Email: firstname.lastname@example.org
As with any addressable network, having duplicate addresses is an issue. On Modbus Plus networks, one of three things can occur. Modicon technical support disagrees on this subject but in my 30+ years of working with these networks all over the world, I have proven differently many, many times.
The first, and most likely event to occur, the node that is being added to a network with the same address, will simply not be allowed to join the network.
The second thing that may occur, the node that is being added to the network will displace the existing node with the same address, assuming its’ place upon the network.
The third thing that may occur, is that when connecting the new node to the network with an existing node address is that the two nodes alternate joining and dropping off of the network.
The second and third options are obviously not desirable results. For this reason ALWAYS be certain of what addresses are existing on any given network. Utilizing a network discovery tool such as MBPStat, should eliminate any dual addressing.
Very recently, while performing a quick troubleshooting procedure upon a Modbus Plus network, I found a unique situation. I knew that I had a duplicate address on my computers’ PCMCIA card. however the plant was down, with no equipment running , and I was just doing a quick error check after repairing an illegal splice on the network. I was located at the MB+ repeater between segments 3 and 4 of this network. I monitored segment 3 for errors, all was OK, then I monitored segment 4 for errors, again all was OK. I reconnected the cables back to the repeater and then went to the end of segment 4 to monitor the entire network for errors. I was surprised to see all “U”‘s on every node! Those familiar with MBPStat, know that this indicates the monitor cannot properly identify the nodes. I went back to the repeater and checked both segments individually, again, all was OK. It was then that I remembered that I was utilizing an already assigned node address. I suspected this may be the issue. I again reconnected the cables back to the repeater, went to the end of segment 4, reset the address to a non-assigned node address. Upon checking the network monitor, it now showed all nodes properly with no errors.This further illustrates the unusual results which may occur in the event of a dual node address.
This is even more reason to be aware of existing addresses when adding any nodes to a network!
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Delta Automation, Inc., located in Richmond Virginia, is an Industry Leader in Industrial Electronics Remanufacturing (depot type repair), On-Site Field Service, New Equipment Sales, and Mature Equipment Sales. Our focus is on Programmable Controllers (PLCs), Drives (VFDs), Control Screens (HMIs) and Peripheral Hardware Support (to include, Software & Firmware). With over 50 years of Repair and Support, we proudly offer our services.