We found 317 posts about Drives & Motors from DO Supply, a global automation parts
reseller focused on hard-to-find and obsolete industrial automation products.
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...
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...
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...
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...
In PowerFlex variable-frequency drives (VFDs), the DC bus functions as the internal power bridge and electrical reservoir between the AC input rectifier and the output inverter stage. Once the incoming AC line voltage is rectified, the DC bus capacitors smooth and stabilize the resulting DC bus voltage by reducing voltage ripple, thereby delivering a steady DC supply to the inverter. They also temporarily absorb the regenerative energy produced during overhauling-load conditions or motor deceleration, reducing rapid voltage fluctuations and improving energy efficiency. This article provides a comprehensive overview of the fundamentals of DC bus voltage in Allen-Bradley PowerFlex drives. Knowledge of pre-charge drive operation, DC bus capacitors, shared DC bus configurations, DC bus regulation, regenerative energy management, and common DC bus-related faults enables engineers and maintenance personnel to maximize the reliability of PowerFlex drives, improve overall system performance...
Modern motor control relies heavily on variable frequency drives, yet the components that safeguard them are often the first to suffer budget cuts. Line reactors, also known as input reactors, are often seen as optional add-ons rather than necessary safety measures. The electrical mechanics underlying reactor protection, the failure types that reactors avoid, and the cost justification for implementing them on each drive installation are all discussed in this article. In simple terms, an input reactor is a three-phase inductor placed between a drive’s input terminals and the incoming AC power source. Its purpose is surprisingly straightforward: it increases the line’s impedance. In a drive environment, this impedance smooths out the abrupt current spikes that occur each time the drive’s rectifier bridge charges its DC bus capacitors, as it resists rapid current changes. Drives convert incoming AC to DC using an SCR bridge rectifier or diode. Because the current is drawn in brief...
Teams with short timeframes set up Rockwell’s PowerFlex drives every day, and most of that work only touches the handful of parameters needed to make a motor spin: voltage, frequency, and a start reference. Once the motor turns, the commissioning checklist gets signed off, and everyone moves on to the next job. But PowerFlex drives feature dozens of secondary parameters that regulate efficiency, thermal load, fault tolerance, and lifespan. When these are left at their defaults and never reviewed, the drive still runs, but often well below its capabilities. Factory settings on a PowerFlex drive exist for one reason: broad compatibility. They are built to work across a wide range of motors and applications, which means they are rarely ideal for any single fixed installation. A default acceleration ramp, carrier frequency, or stall timer is enough to get a drive running. Still, it won’t match the thermal properties of a specific motor, the inertia of a specific load, or the electrical...
It’s no secret that AC drives, particularly variable frequency drives, have been efficiency and productivity boosters for automation facilities. Manufacturers boast about how their drives can pay for themselves with the money you save with reduced energy costs, while also reducing mechanical wear throughout the system For those who want to stick to their guns and continue using their conventional motor controller until it breaks, there is a cost to waiting. AC drives are effective because they address many of the inherent inefficiencies and mechanical stresses associated with controlling motor speed using fixed-speed equipment. Without one, a facility may be paying a hidden tax through wasted energy, increased maintenance, reduced process control, and premature equipment wear. One of the biggest arguments against installing an AC drive is often the initial cost of the system. One may argue that an AC drive may be more difficult to install, and if done improperly, could lead to even...
In a VFD-dominated industrial world, soft starters still have their place in motor control. They are a reliable way to protect your motors, the loads they move, and the systems they’re attached to. On top of that, they fit nicely into a budget-conscious build when a facility doesn’t need the extra features or programming that VFDs offer. Not every soft starter is built for the same job. Some are basic starters designed for simple start-and-stop control. Others are more advanced units with stronger protection features, better diagnostics, communication options, and more control over how the motor starts and stops. Each type has its own advantages, limitations, and best-fit applications. A variable frequency drive, or VFD, is the more common component to pair with a motor for industrial control. VFDs can control motor speed, improve efficiency in variable-speed applications, support advanced diagnostics, and, in higher-end models, offer features such as regenerative operation and...
