AutomationDirect - Motion Control Tips

VFDs with integrated PLCs for motion and machine controls: Programming and setup considerations

March 24, 2019 By Lisa Eitel Leave a Comment

Today’s ac drives can be controlled by either an external or internal PLC. Those with built-in controls move machine intelligence to the edge.

By Jeff Payne • AutomationDirect

Though ac drives can operate in standalone, they often integrate into automation systems to control speed of three-phase ac motors that commonly run conveyors, fans, and pumps. For such speed control, ac drives most often pair with PLCs. But ac drives are becoming more intelligent … and some now include built-in PLCs to work as smart drives. These smart ac drives are compact; add intelligence at the edge of machinery; include inverters capable of more than just typical speed control; and accept the setting of myriad parameters.

In this feature, we’ll detail how to integrate smart ac drives and the applications for which they make the most sense.

Many VFDs, such as this AutomationDirect DURApulse GS4 series AC drive, can be controlled and monitored by an external PLC.

Review of how ac drives work

An ac drive is often called a variable frequency drive (VFD), adjustable frequency drive (AFD), or frequency inverter. We use the term VFD for its main function of varying the speed of a three-phase ac induction motor. VFDs also provide motor overload protection, non-emergency starting and stopping, and control of acceleration and deceleration.

VFD benefits significantly boost the efficiency of many applications. In addition, they gradually accelerate the motor — which in turn reduces inrush current during motor startup. This minimizes both electrical and mechanical stress on the system.

VFDs operate by rectifying incoming ac power to dc and then inverting it back into three-phase ac output power. The voltage and frequency of this inverted output is controlled by the drive to vary the speed of a three-phase ac induction motor.

Control modes include volts per Hz (V/f), V/f with encoder, open-loop vector, and closed-loop vector control. These methods all use a pulse-width modulation (PWM) voltage waveforms; they’re well-developed motor control methods needing some level of automation to control the drive.

VFD control methods

A VFD is controlled by discrete inputs (two or three-wire control), analog inputs and/or digital communications. In its simplest form, a VFD can be manually controlled using the built-in digital keypad’s run/stop buttons. This keypad also allows setting of the drive speed and other parameters, as well as monitoring of drive status variables. Manual pushbuttons can also be wired to the drive in a two or three-wire configuration to control basic functions.

A two-wire control setup provides a run command input and a direction input to the drive. The run command must remain high (on) for the drive to run the motor. The direction command controls forward and reverse motor rotation. Deactivating the run command stops the motor.

With three-wire control of a drive, a stop command is added to the drive control inputs. To activate the drive, the stop command must be high, often through use of a normally closed (NC) pushbutton or an NC relay contact. A momentary run command is all that is needed to activate the drive.

Both two or three-wire drive control methods can be via manual pushbuttons, PLC-activated relay outputs, or PLC discrete signal outputs. Some drives also have programmable functions such as jog, speed change, and acceleration and deceleration control.

Analog signals can also help control drives to deliver speed-control or tension-control functions. Signals take the form of analog 0 to 10 Vdc voltages, analog 0-to-20-mA or 4-to-20-mA current, or potentiometer signals. A two or three-wire discrete control method is still needed to start and stop the drive.

Digital communications between PLCs and VFDs

In addition to discrete and analog inputs, PLCs often control VFDs using digital communications such as Modbus ASCII and Modbus RTU, or via industrial Ethernet protocols specifically created for real-time control. These digital communications can control all drive functions or work in concert with discrete and analog signals. This two-way digital communication often enables all drive commands to be controlled by a PLC, as well as monitoring all drive parameter and reading drive variable, status and fault codes. This can include more than 100 commands, parameters, and status and fault codes.

Serial or Ethernet communication from the PLC can issue speed references, run, direction and jog commands. It can also adjust motor parameters such as voltage and amps and run parameters associated with set acceleration and deceleration times, S curves, and skip frequencies. Other digital parameters include the issuing multi-function input commands and triggering functions just as a discrete input would. Target frequency and current (and many other analog and preset parameters) are also available for control and monitoring using digital communication. Where the PLC communicates with the drive to monitor status and fault codes, it might compare the frequency command to output frequency or the output current to rated current or motor rpm.

The monitoring of drive faults is also enhanced by digital communication. Instead of just a ‘fault present’ discrete signal, the system can register dozens of error codes — including overcurrent, overvoltage, overtemperature, overload, low voltage, and more.

Upfront programming of the drive’s monitoring and control functions (through discrete communication) makes for a more intelligent system. A serial or Ethernet link between the PLC and drive(s) is required; with Ethernet, a hub or a switch is also needed. The ability to configure, control, and monitor the drive from the PLC via digital communications helps futureproof automated systems.

These WEG-CFW300 ac drives from AutomationDirect offer high performance in a compact size, along with a built-in operator interface and a SoftPLC. They eliminate the need to purchase, install, and integrate an external PLC with the drive.

Programming ac drives with built-in PLCs

As mentioned, PLC control of VFDs is well-developed with many configuration and monitoring options. But devices at the machine edges are becoming smarter … and VFDs with built-in PLCs are no exception. These VFDs provide all the precise variable speed-control functions of separate PLC-controlled drives, but in one compact package. Such Smart drives typically have a built-in operator interface panel and a SoftPLC. Via the interface panel, it is possible to control the VFD and view (and adjust) its parameters. A typical keypad toggles between parameter numbers to show position or value. Up and down buttons let operators change the parameter number or its value. Anotehr button lets operators run and stop the drive and reset drive faults. A variety of plug-in option modules are typically available for additional I/O … and to add additional communication protocols.

In an array of applications, smart drives can often control entire machines or systems … helping negate the need to purchase, install, and integrate separate PLCs and operator interfaces.

Some vendors provide free PC-based programming software for the SoftPLC portion of the drive — to let design engineers create custom-tailored control schemes. These then download from the PC to the drive (often via a USB connection). Such software typically includes ladder diagram programming for the creation of function blocks to monitor inputs, operate the drive, and control outputs. Besides controlling the VFD housed in the same package, the SoftPLC can also work to monitor additional components on the plant floor — including other VFDs.

A VFD with a built-in Soft PLC can monitor sensors and run programmed logic to properly convey products.

Driving conveyor, mixer, and other applications

Common applications for smart drives include packaging machines, mixers, kneaders, and dosing pumps. Other applications include the control of fans, exhausts, centrifugal pumps, granulators, palletizers, stirrers, and conveyor belts. Many conveyor or gate applications need to monitor inputs from a few sensors to properly control a VFD as well as an output to trigger a solenoid. Here a carefully selected smart drive having a built-in PLC (meeting full-load amperage, overload, and temperature requirements) can monitor sensors; make programmed decisions; and control field devices.

Jeff Payne is a product manager for the Drives & Motors Group at AutomationDirect. Before joining the company 20 years ago, he managed, designed, programmed, installed, maintained, and repaired a wide variety of automated equipment. He’s worked in the field of industrial automation for nearly 28 years and earned a degree in Industrial Systems Technology and Industrial Automation from Lanier Technical College.

SureStep IP65 rated stepper motors from AutomationDirect

March 7, 2019 By Miles Budimir Leave a Comment

AutomationDirect has added motors designed for washdown environments to its stepper systems product line. SureStep IP65 rated high-torque stepping motors are completely protected from solids and dust ingress and from low pressure water jets from any direction, making them suitable for many washdown applications.

These fully sealed, single-shaft motors are available with industry-standard NEMA 17, 23, and 34 mounting flanges and provide holding torque from 61 to 1,288 oz-in. The motors use 2-phase technology with 200 full steps per revolution or 1.8 degrees per full step.

The square-frame or “high-torque” style of these stepping motors is the latest in bipolar motor technology, resulting in the best torque to volume ratio. Waterproof white epoxy coating on the motor laminations and special bearings and seals keep moisture out of the motor.

IP65 motors are available in single-shaft configurations and have a 1-ft. cable and locking connector. Extension cables with mating IP65 connector are available in 6, 10 and 20 ft lengths. The stepper motors are CE compliant and have a 1-year warranty.

To learn more, visit www.automationdirect.com/ip65-stepper-motors.

RHINO PSV dc power supplies from AutomationDirect

January 18, 2019 By Lisa Eitel Leave a Comment

AutomationDirect now sells economical PSV series power supplies and universal battery control modules as part of the RHINO DC power supplies lineup. RHINO PSV Value series DIN rail power supplies come in a wide selection of voltage and wattage ranges. 5-V RHINO DC supplies come in 15 and 25-watt ratings with 12-V supplies at 48 W. 24-V DC supplies come in 30, 50, 100, 120, 240 and 480W; and 48-V supplies are rated up to 120 W.

15 to 100-W models (in ultra-compact plastic housings) have efficiency ratings to 89.0% … full power operating temperature ranges from −10°C to +55°C … and are NEC Class 2 / Limited Power Source (LPS) certified.

120 to 480-W RHINO power supplies have a metal housing; provide full power from −10°C to +50°C; and maintain efficiencies to 88.0%. Plus these models have a built-in constant current circuit for reactive loads.

Starting at $32.00, RHINO PSV series DC power supplies are UL/cUL saw, CE approved and have a three-year warranty.

Also added are universal battery control modules (starting at $30.00) that provide uninterruptible 24VDC bus voltage and offer battery protection for over voltage, deep discharge, short circuit and reverse connection. Alarm outputs indicate input, output and battery conditions. For more information, visit automationdirect.com/dc-power-supplies.

In business since 1994, AutomationDirect is a distributor offering thousands of industrial automation products for electrical control systems, including PLCs, operator interfaces, AC drives, motors, stepper systems, sensors, motor controls, enclosures and more. Their prices are typically well below the list price of more traditional automation companies because of their business model and focus on efficiency and the majority of their products are stocked for same-day shipping. Plus, get free two-day delivery on orders over $49; some limitations apply.

Premium-efficiency, cast-iron three-phase ac motors from AutomationDirect

December 18, 2018 By Miles Budimir Leave a Comment

IronHorse MTCP2 industrial duty motors meet the premium efficiency requirements of the Energy Independence and Security Act of 2007. MTCP2 motors are offered in T-Frame (1 to 300 hp) and TC-Frame/C-Face (1 to 30 hp). C-face kits are available for motors over 30 hp.

These motors are available in 1,200, 1,800, and 3,600 RPM and have TEFC (Totally Enclosed Fan Cooled) enclosures with cast-iron frame and ribbed design for maximum cooling. The motors feature full length, cast-iron mounting feet, steel fan cover, and cast-iron junction box with rubber gasket and rubber dust cover.

MTCP2 motors have premium quality ball bearings (1 to 75 hp) or roller bearings (100 to 300 hp) with maintenance free bearings on 10 hp and below. V-ring shaft seals are used on the drive end and opposite drive end. The motors are electrically reversible and have Class F winding insulation.

MTCP2-series motors start at $180.00, have a two-year warranty, and are CSA and CE approved. Available accessories include bases, junction boxes, fans and fan shrouds.

To learn more, visit www.automationdirect.com.

AutomationDirect adds compact WEG VFD drives

December 13, 2018 By Miles Budimir Leave a Comment

AutomationDirect has added a new line of ac variable frequency drives (VFD) for motor speed control and other industrial control applications.

The WEG CFW300 variable frequency drive is a high-performance VFD for three-phase induction motors. It’s suitable for applications on machines or equipment that require precise control with easy setup and operation. The CFW300 features a compact size with contactor-style electrical connections (top in / bottom out). The VFD’s performance can be scaled to match the application by selecting WEG vector control (VVW) or scalar control (V/Hz).

The CFW300 includes a built-in keypad and SoftPLC with free WEG Programming Suite (WPS) software for custom tailored control schemes. The integrated WPS tool assists in the creation of automation applications, allowing graphical monitoring, parameter setting and programming in Ladder language (IEC 61131-3).

Built-in I/O capabilities include four configurable (PNP or NPN) digital inputs, one 0.5 A / 250 Vac relay output, and one 0 to 10 VDdc/ 4 to 20 mA analog input. A variety of plug-in option modules for additional I/O and communications protocols can be added to extend capabilities. A remote keypad and flash memory module are also available.

Starting at $138.00, sixteen units are available from 1/4 hp to 5 hp. Single-phase 100 to 127 Vac, and single or three-phase 200 to 240 Vac power supply options are available. WEG CFW300 series AC drives are cUL, CE approved and are backed by an 18-month warranty.

For more information, visit www.automationdirect.com.

AutomationDirect adds SureStep stepper system motors, encoders and inertia dampers

November 2, 2018 By Miles Budimir Leave a Comment

New stepper motors, encoders and inertia dampers have been added to the SureStep system of step motor control. SureStep series high-torque industry-standard NEMA 14, 17, 23, and 34 stepper motors now provide holding torque from 8 to 1,288 oz-in. The new smaller frame size NEMA 14 motors (1.4-in. wide) start at $22.00 and are available in single and dual shaft versions.

The SureStep family has options for open loop control (no encoder), position monitoring (external encoder feedback), and position verification (integrated motor/drives with internal encoder). Replacement and optional encoders (starting at $42.00) are available for standalone dual-shaft motors and standard integrated motor/drives in all NEMA 14, 17, and 23 sizes.

Fixed resolution encoders are available in 400 pulses per revolution (ppr) and 1,000 ppr; new configurable encoders allow resolution selection from 48 to 4,096 ppr (the default is 400 ppr). A free downloadable configuration utility autodetects the encoder and allows ppr selection.

New step motor inertia dampers (starting at $13.00) smooth out steps in a typical step motor, resulting in a quieter and smoother motion when rotating between steps. The dampers also reduce resonance and possible micro oscillations when moving from step to step and can be used as a hand wheel to directly rotate the position of the rotor when power is removed from the motor.

SureStep Stepper System motors, encoders and dampers are CE approved and backed by a one-year warranty.

For more information, visit www.automationdirect.com/stepper-systems.

New integrated stepper motors and drives from AutomationDirect

July 17, 2018 By Miles Budimir Leave a Comment

AutomationDirect has added integrated motors and drives to its SureStep line of stepper motion control products. Integrated stepper motor/drives save panel space, require less wiring and are less expensive.

The new SureStep integrated drive/motor units provide accurate micro-stepping position and speed control for smooth motion and step response and require only two components; power supply and integrated stepper motor/drive. Standard motor/drives and advanced motor/drives are available. Existing SureStep systems require four components including power supply, stepper drive, motor extension cable, and motor.

SureStep advanced integrated motor/drives have available torque from 54 to 340 oz-in. and software-selectable resolutions ranging from 200 steps per revolution. The advanced drives can operate with traditional high-speed inputs, but can also be commanded via 0 to 5 V analog input. An internal indexer can accomplish point-to-point moves controlled via ASCII communication.

Free SureMotion Pro drive configuration software is available for Advanced integrated motor/drives (not required for Standard drives) to easily configure and setup the drive, including drive, motion control mode, I/O, and motor. A Status Monitor screen aids in troubleshooting alarms and faults.

SureStep integrated motor/drives start at $97.00.

For more information, visit www.automationdirect.com/integrated-motor-drives.

Marathon stainless steel and jet pump motors from AutomationDirect

February 20, 2018 By Miles Budimir Leave a Comment

New Marathon Powerwash SXT washdown duty motors are designed for use in food and beverage processing and other washdown environments. The all stainless-steel totally enclosed motors are available in single and three-phase models. C-face with rigid base (footed) and C-face footless mounting options are also available. Marathon stainless steel motor prices start at $309.00.

Jet pump motors are commonly used in commercial and industrial water treatment and processing applications to power centrifugal and hydraulic pumps. Marathon jet pump motors are available in single and three-phase, and in TEFC and Open Drip Proof (ODP) designs. Marathon jet pump motors start at $139.00.

The ODP design lets air circulate through the motor windings for cooling, but prevents drops of liquid from falling into the motor. The increased airflow means lower operating temperatures and increased efficiency when compared to TEFC or TENV motors.

For more information, visit www.automationdirect.com/ac-motors.

AutomationDirect IronHorse MTR2 series general-purpose rolled-steel ac motors

February 1, 2018 By Lisa Eitel Leave a Comment

New MTR2 series IronHorse general-purpose rolled-steel ac motors from AutomationDirect come in 1-phase and 3-phase versions and offer better performance specifications, improved cosmetic appearance and quieter operation.

New single-phase MTR2 rolled-steel motors come in 1800 RPM, 115/230 Vac models. The motors are 56C frame, TEFC, and provide rigid base or C-face mounting. Nameplates include 60 & 50-Hz specifications and reverse wiring instructions.

The 3-phase 208-230/460 Vacrolled steel MTR2 motors come in 1,800 and 3,600 RPM models with TEFC (Totally Enclosed Fan Cooled) frames, cast aluminum end bells and removable mounting bases. Nameplates include 60 & 50-Hz specifications.

MTR2-series motors start at $83.00, have a two-year warranty, meet RoHS and Low Voltage Directives, and are CSA and CE approved. Available accessories include replacement/spare bases, junction boxes, fans, fan shrouds and also Run / Start capacitors for 1-phase motors. For more information, visit automationdirect.com/general-purpose-motors.

PLC basics video: Processor types, I/O modules, and programming

November 16, 2017 By Lisa Eitel Leave a Comment

Programmable logic controllers — or PLCs — are microprocessor-based electronic components that serve as the programmable smarts for simple or isolated applications. Now they’re also finding increased use on integrated machines and more involved automation setups …

PLCs came to being in the 1960s to replace relay-based controls — whole cabinets of relays and impressive runs of wiring in some cases. This trend followed the electrification of manufacturing — and the increasing complexity of design requirements. So traditional hard-wired relays have largely yielded to reconfigurable PLCs. Now, it’s true — primitive hardware and rigid task execution were initial PLC limitations. After all, early PLCs were limited to the electronics of the day.

But as PLCs evolved, they came to have unbeatable reliability. Today, their logic and memory boards, backplane interfaces to I/O modules, and generally heavy-duty circuitry help make PLCs indispensable.

The basic parts of any PLC system include the processor, I/O modules to handle inputs to the controller and outputs to the controlled devices, and some type of user interface which could be as simple as a keypad or a touchscreen interface or a programming link via a PC. The PLC’s processor is programmed via the user interface. The I/O modules are used to bring input signals into the PLC’s CPU and output control signals to controlled devices such as motors, valves, sensors and actuators, among others.

One core PLC strength is how they let engineers write application code to suit specific applications in which they’ll operate — on assembly lines and in machinery and elsewhere on factory floors … with other electrical, mechanical, and electronic equipment. Here, the original form of PLC programming known as ladder logic — finding its roots in good ol’ relay logic — is still dominant.

Rumors of the PLC’s demise have been greatly exaggerated. Despite industry predictions to the contrary, PLCs are still by far the most common choice for standalone or single-axis motion. Such applications are seeing more inroads from motor drives sporting controller functions. These motor drives excel in machine designs that still need PLC functions with multiple interfaces — including Ethernet communications and digital I/O, for example. Because such motor drives can also incorporate motion controls delivering S-curve, camming, and freeform motion profiles, OEMs are more likely to pick them than PACs in otherwise-simple designs eliminating standalone PLCs.

Part of the PLC’s enduring use is how their cost — at least on the hardware side — has consistently gone down over the decades, even as their capabilities have grown. Some PLCs are just a few hundred dollars. One caveat here is that PLC software sold through license agreements can increase overall design costs.

In addition to ladder logic, some PLCs can be programmed in higher-level languages such as C and BASIC or run proprietary languages. Many offerings aim to homogenize industrial PLC programming, and all aim to reduce work for end users. For more videos like, this visit designworldonline.com.