Industrial automation systems rely on industry-grade Ethernet switches to provide reliable communication among Variable Frequency Drives (VFDs), Programmable Logic Controllers (PLCs), remote I/O modules, HMIs (Human-Machine Interfaces), and other networked devices. Selecting the right Ethernet switch is a key consideration when designing, upgrading, or expanding an industrial network. Industrial Ethernet switches are primarily classified as unmanaged or managed. Unmanaged switches require no configuration and generally provide basic plug-and-play connectivity. These switches are used in small, basic networks that do not need redundancy, traffic control, advanced monitoring, or diagnostic capabilities. Conversely, managed Ethernet switches offer control over network functionality, providing greater visibility. They also support diagnostic protocols, including the Simple Network Management Protocol (SNMP). In addition, various managed Ethernet switch models do support access control...
A voltage sag on the incoming AC line may seem like a minor issue with little effect on your drive, but this isn’t always true. Every frequency inverter has a DC bus that briefly absorbs fluctuations, deciding whether the sag causes a trip, an alarm, or lets the drive ride through the event. This article covers each part of that process, drawing on Schneider Electric’s insight into where the DC bus voltage comes from, and explains the internal chain from rectifier to DC bus and its protection, with examples of products offering this capability. A Diagram of Voltage Sag A rectifier converts incoming three-phase AC to DC and charges the capacitors on the DC bus . For a typical diode-rectifier drive, the DC bus is roughly 1.35–1.41 times the RMS line voltage, depending on drive design and operating conditions. So where the input voltage is normally 480 V, the DC bus would read around 677 V. This lines up with figures quoted by Schneider Electric, who state that a 480V system has an...
A failure history log is kept on file by all contemporary variable frequency drives. Every problem the drive has encountered is recorded, together with the precise operating parameters at the time of each trip: output current, DC bus voltage, output frequency, heatsink temperature, and, most of the time, a timestamp that puts each incident in chronological order. For a maintenance engineer in front of a stopped machine, this record is the most comprehensive diagnostic data source. In industrial maintenance, it is also the diagnostic tool that is most often disregarded. For example, the fault history is cleared before it can be read, or the reset button is pressed before data can be recorded. This article covers what drive fault history contains, how to interpret it properly, and why the quickest route from a tripped drive to a permanently fixed defect is to use it methodically. Most drives keep some form of fault history, but the amount of stored information depends on the model. This...
Motor control comes in all different shapes and sizes depending on its use case and feature set. Soft starters, for example, are a fantastic solution when the goal is to bring a motor up to speed gradually without subjecting your equipment to the sudden shock of an across-the-line start. By gradually controlling the power delivered to the motor during startup, they can reduce starting current, limit mechanical shock, and provide a smoother acceleration. However, they aren’t a fit for every motor application. The biggest limitations usually appear after the motor starts. Once acceleration is complete, a soft starter typically supplies the motor at full line conditions, often through a bypass contactor, and provides far less continuous motor control than a variable-frequency drive. There are also applications where a soft starter adds complexity and expense without providing much benefit. Understanding these situations can make the difference between choosing a controller that fits the...
Unplanned downtime is one of the biggest concerns in industrial production. A single control-system failure can stop an entire production line, leading to lost material, idle equipment, missed deadlines, and costly delays. For this reason, high-uptime ControlLogix systems are designed around more than just the controller itself. Controller redundancy, resilient EtherNet/IP networks, redundant power, distributed I/O, and advanced diagnostics can all help keep a system running when something goes wrong. However, simply installing higher-end hardware does not guarantee reliability. The overall architecture still needs to reduce single points of failure and allow the system to recover quickly when a fault occurs. High-uptime control systems should be engineered to withstand single-component hardware failures while maintaining continuous operation — without interrupting data execution or process outputs. The ControlLogix platform accomplishes this through a synchronized, redundant chassis...
Distributed control systems, essential to modern industrial automation, need distinct hardware components to communicate seamlessly across large facility floors. The Programmable Logic Controller (PLC) is at the core of this system. PLCs execute control logic, process sensor and I/O data, command field devices, and exchange information with HMIs, SCADA systems, drives, remote I/O, and higher-level systems. But a PLC’s effectiveness depends on the communication networks that connect it to company databases, input/output (I/O) modules, human-machine interfaces (HMIs), and supervisory control and data acquisition (SCADA) systems. Over the last several decades, simple proprietary serial lines have given way to sophisticated, high-speed Ethernet-based protocols. Determinism, bandwidth, distance, setup complexity, and cybersecurity must all be balanced to choose the best protocol, which is seldom a simple technical task. Automation engineers must understand these trade-offs to build...
A variable frequency drive (VFD) rarely fails suddenly. Instead, before a VFD stops reliably operating a motor, it will begin to show signs of degradation, starting with symptoms like increasing fault counts, distinct noises, or thermal stress. These eventually culminate in signs of the drive’s aging internal components. If maintenance crews spot those early warnings, they may have time to install a new VFD before failure, keeping production running. A VFD’s service life is mainly controlled by two wear-limited parts with documented, temperature-dependent life expectancies: the electrolytic capacitor that forms the DC bus, and the cooling fan. Aging in both components is slow — they don’t fail on a fixed date but degrade gradually, so assessing age means understanding behavior, not just install date. ABB’s ACS550 documentation (page 67, section 4) and the ACSM1 VLT FC 302 documentation (page 4, section 2) describe this best. Electrolytic capacitors on the DC-link circuit smooth the...
One of the most annoying diagnostic situations in industrial drive maintenance is a nuisance overcurrent issue. When the PowerFlex trips, production stops, the operator resets it, and it functions normally for many hours before tripping again for no apparent reason. Nuisance overcurrent faults are condition-dependent, sporadic, and seldom self-explanatory from the fault code alone, in contrast to a hard fault brought on by an obviously malfunctioning component. An overcurrent fault is a precise diagnostic signal intended to prevent damage to the motor, drive, and related equipment. It shows up as a strong, abrupt current spike that exceeds the drive’s hardware limits. Diagnosing any PowerFlex model, from the tiny 525 to the architecture-class 755T, depends on understanding what causes these spikes and distinguishing between hardware-level and software-level overcurrent detection. When diagnosing a PowerFlex overcurrent problem, the first thing to consider is whether the event is...
One of the most important decisions in industrial motor control is choosing the right Variable Frequency Drive (VFD), or AC drive, to match your motor and application requirements. Proper AC drive selection begins with understanding the mechanical load characteristics because the load type determines the current and torque requirements the selected AC drive and connected motor must meet across all operating speeds. An appropriately sized AC drive provides adequate continuous and overload current capability to generate the required motor torque while operating reliably. Selecting an incorrectly configured or improperly sized AC drive often results in insufficient starting or accelerating torque, excessive drive or motor heating, reduced efficiency, nuisance trips, and premature equipment failure. In contrast, an AC drive that is correctly matched to the specified load type helps improve motor performance, operation reliability, energy efficiency, and overall system lifespan. Because of...
When choosing a PLC, the system’s architecture affects all subsequent engineering work, from how control panels are drawn to the cost of maintaining the system over years of service. Most PLCs fall into one of two competing design philosophies: modular architecture, where the I/O, CPU, and power supply are separate elements on a common backplane, or fixed architecture, where all of these are combined in a single housing. Every major PLC vendor offers product lines that follow both designs, and understanding how each platform is laid out helps an engineer pair architecture to application rather than defaulting to whatever solution is already sitting on the shelf. Comparing the five largest control vendors in Europe, North America, and Asia – Rockwell, Siemens, Schneider Electric, Mitsubishi, and Omron – all of which market modular and fixed models side by side – shows which factors vendors weigh when dividing fixed and modular I/O architectures. The real tradeoffs come down not to...
Rockwell Automation’s high-power servo drive platform, the Kinetix 7000, is intended for large-frame motion applications. Commonly paired with MP-Series motors, the drive was available in power ratings from 22 to 149 kW, making it well suited for applications involving high inertia, large mechanical loads, and demanding acceleration and deceleration cycles. One challenge that arises with these applications is managing regenerative energy. When a servo motor decelerates or is driven by its mechanical load, it can operate as a generator and return excess energy back to the drive’s DC bus. However, if that energy has nowhere to go, the rising bus voltage can cause an overvoltage fault. How the Kinetix 7000 handles this energy depends on the system’s power configuration. A drive can operate from its own AC line connection, while systems with greater regenerative demands can incorporate external shunt equipment or a regenerative power supply such as the 8720MC-RPS . Kinetix 7000 drives can...
When selecting a soft starter for your motor control application, it helps to know what each setting does and how it affects your motor’s behavior. However, as different modes and features are added to a soft starter, it can be a bit overwhelming to determine the optimal choice for your application. After all, there is kick start, current ramp, torque control, linear acceleration, full-voltage start, and more. Today we will narrow down this list and go over the two more popular starting modes, voltage ramp and current limit start, explain what makes them different, and even why they might be used together. Order SMC Flex Soft Starters Here Before we dive into how these soft starter features work, it helps to first briefly go over what a soft starter is and does. If you would like a much more in-depth explanation and overview, we encourage you to read our full guide to soft starters here . The general idea of a soft starter is to place this device between an induction motor and its...
When it comes to PowerFlex drives, the gap between the most cost-effective model and the most technologically advanced unit is quite significant. From the humble PowerFlex 4M and 520-series controllers offering simple and dependable motor control, to the flagship PowerFlex 755T family built with smart features in mind for demanding applications. Technically speaking, both ends of the lineup are doing the same basic job. They take incoming electrical power and control how it’s delivered to the motor. But that’s like comparing a 20-year-old work truck and a newer, fully equipped heavy-duty model. Sure, both can get you down the road, but one is designed to handle a much wider range of conditions, loads, and specialized tasks. It’s this gap that makes the PowerFlex line interesting to compare. Moving from an entry-level drive to a high-performance model doesn’t just add a few settings or a larger enclosure, but rather more sophisticated motor control, beefed-up hardware, and a suite of...
For more than 20 years, one of the most extensively used programmable logic controller (PLC) platforms in small and medium-sized industrial facilities has been the MicroLogix family, which includes the 1000 , 1100 , 1200 , 1400 , and 1500 series. Each MicroLogix controller combines the CPU, power supply, communication interfaces, and fixed or semi-modular input/output (I/O) into a single chassis, making it a small, self-contained automation system. MicroLogix streamlines installation, minimizes cabinet space, and reduces overall system complexity compared to modular PLC systems like CompactLogix and ControlLogix, which distribute these components across a backplane. By enabling modest extension with Bulletin 1769 Compact I/O modules, the MicroLogix 1500 further increases versatility. MicroLogix controllers have enough processing power for a variety of industrial applications, while being small by today’s standards. They handle 16 to several hundred discrete I/O points, provide between...
Automation equipment gets phased out all the time. We see it with PLCs, drives, and everything in between. However, obsolescence doesn’t mean the equipment is unusable or should be replaced immediately. This is the case for the SMC Dialog Plus soft starter family. Discontinued in 2014 as Rockwell phased out the mature product family, the successor to this soft starter family is the SMC-3 , SMC Flex , or the SMC-50 . The question is now whether the SMC Dialog Plus is still worth using or if its newer replacements are a better buy. There are many reasons why someone would want a legacy product over a newer offering. Sometimes it’s just easier to get the same product you know will be reliable and work for your system. Other times the cost of upgrading might not be worth the potential productivity increase of a newer system. Often, a facility needs a direct replacement as soon as possible when their old one breaks. There is no time to fit, program, and upgrade to newer hardware when every...
