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Product category: Industrial Drives/Controls
News Release from: ABB Automation Tech (Drives and Motors) | Subject: Machinery drive
Edited by the Engineeringtalk Editorial Team on 26 February 2007

Standard AC drives enter servo
performance arena

Machinery builders can now specify one drive for a variety of motor types along with an appropriate feedback device, depending on the application.

ABB has designed a new drive which it claims is the most adaptable in the market, allowing control of synchronous or asynchronous motors, either open loop or closed loop With the new drive, machinery builders only need to specify one drive for a variety of motor types along with an appropriate feedback device, depending on the application

The new ABB machinery drive, rated from 0.75 to 45kW, uses standard AC drive technology but with significant performance improvements that are set to take ABB into the servo performance arena.

It is targeted at machinery builders and will open up new applications for ABB such as smaller processing line drives for rubber and plastics machines.

"While ABB is a well established supplier of main drives to rubber and plastic machines, the new machinery drive gives us access to the many smaller precision drive applications found in this industry", says Steve Ruddell, General Manager Drives and Motors.

Likewise, ABB's expertise in drives for large harbour and industrial cranes is extended to smaller power material handling equipment and cranes.

The new drive also fulfills the need of demanding paper applications, like small power winders, calanders, slitters and cutters.

"The ABB machinery drive is compatible with the needs of various converting machines, such as coating, calandering, colouring, cleaning, laminating paper, plastic, rubber, foil and food stuffs", says Ruddell.

The drive is the result of an intensive four year R and D program that considered all aspects of the product from the manufacturing techniques, through new hardware and software developments, to evolving present standard AC drive principles.

Key developments that have attributed to the design of the new drive are: direct torque control; broader selection of feedback devices; communications and fieldbus intelligence; user friendly construction; and better overall system performance.

"During the last 10 years, DTC (direct torque control) has gained extensive acceptance from industrial drives customers and it has become a benchmark in the high performance drives market globally", says Ruddell.

"Now DTC is adjusted to fulfill the demanding machinery builders' requirements".

"DTC is tuned for accurate control of induction, synchronous and asynchronous servo and torque motors with various feedback devices".

DTC features a very fast torque control loop, which takes it into the pure servo drive arena where torque control loops of between 62.5 to 250us are achieved.

Machine builders often require various positioning and synchronisation options, including centralised position control from motion controller or distributed motion control.

The ABB machinery drive has both options.

With positioning and synchronisation control of the ABB machinery drive at 500us, the drive is suitable for the most demanding machinery uses.

Reference handling inside the drive is configurable starting from 250us for optimum performance.

The drive retains some key DTC features from other ABB ranges.

For example, flux optimisation is a feature associated with energy saving.

Although machine builders may not require such a feature, it does mean that with the machinery drive, one product can be used, not only for the core machine control applications but also for auxiliary applications such as pumps and fans.

The customer benefits from the same user interface, same spare parts, same single set of documentation and training.

Traditional servo drives can not control pumps and fans as servos require feedback devices.

The flying start feature is also retained by the machinery drive.

It has excellent open and closed loop performance and the drives various speed feedback options further improve the flying start performance.

Furthermore, the faster the torque control the faster the drive can recover control when power supply returns.

Flying start is important for continuous process applications, where even very short process interruptions may result in loss of long period production.

The ABB machinery drive has a library of different filter function blocks.

Software filters are used to tune the motor control and application software so that torsional vibrations of mechanical systems or instability of speed or torque reference signals from external systems can be reduced or eliminated.

The ABB machinery drive offers access, for the first time, to the widest range of speed and position feedback devices such as resolvers, absolute encoders and incremental encoders.

This wider choice of feedback devices overcomes potential problems with incremental encoders, which, during a power interruption, can lose their position or count.

This makes them unsuitable for the most demanding machinery applications that require positioning and synchronisation.

"While the drive has excellent open loop capabilities, many of the new applications require even more precise control and as such the drive is compatible with all feedback devices including absolute encoders, resolvers and 'normal' incremental encoders", says Ruddell.

One of the keys to DTC's accurate speed, torque and position control is the motor model.

In the ABB machinery drive, the speed feedback from the motor can be used to fine tune this motor model, thereby improving the control performance to unprecedented levels.

ABB's feedback device interfaces come with inbuilt intelligence via a microprocessor or FPGA (field programmable gate array).

The interface itself processes signals received from the device attached to motor shaft.

The output signal from the feedback device rapidly processes speed or position information and can be used as such by speed, torque or position controllers inside the drives control unit.

The ABB machinery drive has an I/O sampling system and fieldbus communications that offer good links to external control systems.

For example, the sampling time of each I/O can vary and sampling time levels can be prioritised.

This means I/O utilisation can be optimised and the main processor load can be controlled for the best overall control performance.

ABB machinery drive aims to be compatible with all the major fieldbuses including Profibus, DeviceNet, CANopen and Ethernet.

The fieldbus interfaces option modules have their own in-built intelligence via a micro processor or fieldbus specific ASIC (application specific integrated circuit).

Signals from the fieldbus are processed in the interface module and then transferred through fast internal link to the control software.

This provides a very open architecture for different fieldbuses.

The ABB machinery drive design breaks new ground by allowing customers to specify dedicated functionality which can be assembled or programmed immediately before dispatch to the customer.

Features such as fieldbus, digital and analogue extension and feedback interfaces are simply plugged in and can be configured by local ABB distributors; at the machine builder's workshop; or on a customer's site.

At the heart of the design are three main units: power unit, control unit and memory unit.

The power unit is dependent on required power and control hardware units remain the same, while the removable memory unit stores software that can be varied.

If the power unit or control unit is replaced, the drive can be recommissioned without drive knowledge.

There is no need to set any parameters, as the complete settings are available within the removable memory.

ABB has focused on achieving the best overall system performance by designing faster signal processing such that the time delay from control reference change to motor shaft torque change is among the quickest on the market.

"The design team set out to ensure that each core software and hardware element supported each others performance", explains Ruddell.

"For example, if we have a control loop within the speed controller running at 250us, then both I/O or incoming signal and encoder or speed feedback sampling supports the same 250us loop".

"Reference signals will not be lost".

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