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Intelligent inverters set new standard for energy efficiency

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Intelligent inverters set new standard for energy efficiencyMitsubishi Electric has developed a new generation of drive technology for its new FR-F800 variable-frequency drives that are claimed to offer previously unattainable performance in terms of energy saving, optimised speed control, simple start-up, connectivity and the versatility of its features. Designed primarily for pump and fan applications, the FR-F800 is equally suitable for compressors and HVAC applications. It features many innovative functions that ensure accurate control, while also achieving 98 per cent energy efficiency, yet the new F800 drives are priced the same as their predecessors.

There are initially six units in the series, three covering the 0.75kW–110kW range (200V–240V input) and three more rated from 0.75kW–630kW (380V–500V input).

At the heart of the all-new FR-F800 is a bespoke PID controller and on-board PLC (based on the Mitsubishi L-series PLC) that provide the drive with true standalone control capabilities. For instance, it can control fans, pumps and compressors directly, thanks to on-board intelligence, I/O, communications, plus expansion slots for adding further I/O and/or protocol-specific communications. In some cases this can avoid the need for a separate PID controller or PLC. Built-in PID functions include a pump-stir function, upper and lower limit pre-warnings, pipe burst detection, dry run protection, water hammer prevention and automatic tuning.

Control multiple pumps from one drive

To enhance its capabilities, the F800 is fitted with a second PID controller. The drive can be used to control multiple pumps, allowing for variable-speed control and the energy efficiency benefits that brings; some pumps can be speed-controlled while others are running effectively Direct On Line (DOL). It can even run pump cleaning cycles automatically, to a schedule or on demand, which should be of interest to operators of waste water sites where features such as this have historically not always been effective.

Instead of relying on single set points for trip activation, an algorithm in the drive can effectively detect the fan or pump torque curve of the attached load and react appropriately when operational limits are approached, which means an end to nuisance trips caused by unusual but not critical load variations. Operationally, this means the pump can help users determine whether a pump is blocked or there is a build-up of dirt on the impeller, for example.

Far fewer false alarms means more uptime, fewer maintenance visits and faster responses to genuine issues such as jammed pumps, broken impellers and snapped belts - all of which can now be more accurately detected by the drive.

Another advanced feature of the F800 is a motor preheat function, which aids smooth start-up, dispels condensation and prevents damage due to freezing in outdoor conditions; it also avoids the cost and complexity of installing trace heating. Its real-time control capabilities can also detect and reduce vibration due to mechanical resonance, protecting other equipment from excessive wear, mechanical damage and premature failure. Vibration is detected by monitoring the drive current waveform, with no need to install accelerometers on the rotating machine itself.

At the other end of the scale, in the event of an emergency situation a 'fireman' (fire override) keeps extraction fans and water pumps running regardless of warning or alarm levels being reached, even to the point of the drive's total destruction.

Intelligent cooling fans

Improving energy efficiency for an already efficient product is all about making small advancements on many fronts and the Mitsubishi F800 has a wide range of dedicated features and functions that deliver efficient operation. For example, during standby all unnecessary circuits are shut down to reduce energy usage. Advanced Optimum Excitation Control (AOEC) maximises energy savings even for high-torque loads, while intelligent cooling fans only activate when required because a set point temperature has been reached. In addition, the F800 is capable of controlling the external control panel cooling fans based on the control panel temperature (using a temperature sensor within the F800); this avoids the need for a thermometer within the panel, which saves panel costs.

A related feature is that the F800 provides plug-and-play auto tuning for both induction motors and high-efficiency permanent magnet motors. For ease of set up, a one-touch Digital Dial allows direct access to all important parameters, while connection to graphical operator terminals and HMIs is also very straightforward. Alternatively an optional six-line LCD display includes an easy start-up wizard function. This display is also able to display customised text messages relating to the drive or controller functions - or, indeed, other process parameters if the onboard controller is being used to monitor and control an entire process. If required, the display can be unclipped from the drive and mounted on the panel door instead. HMI auto-detect capability means connection to an HMI is straightforward.

To enhance the reliability of the F800, fault finding is aided by a built-in data logging and tracing function, with data stored on a USB stick that can then be used to transfer the data to a PC for analysis and/or archiving. The same USB port can also be used for uploading and downloading drive parameters and PLC programs (note that the FR Configurator 2 software for programming the drive and PLC functions is provided free of charge). A remote VNC connection means that users can monitor the drive and check diagnostic data using virtually any mobile device that has an internet connection and web browser.

Intelligent predictive maintenance is achieved through the monitoring of critical components such as power capacitors and cooling fans. A two-channel emergency stop provides a safe shutdown (Safe Torque Off, STO) which can prevent damage to the drive as well as providing a safety function to protect personnel and equipment.

As with all new products launched by Mitsubishi Electric, the F800 has been designed for backwards-compatibility with earlier generations of drive (F700 and F500). Existing installations can be upgraded to a new F800 in a simple unplug and swap-out process; if necessary, the F800 can be de-tuned so that the reaction times mimic those provided by older drives.

Communications options

With network connectivity now of major importance, the F800 is equipped with RS485, Modbus and BacNet as standard. In addition, expansion modules can be installed to provide communications via the following protocols: CC-Link, Profibus, Ethernet, EtherCat, SSCNET III, DeviceNet and Lonworks. A wide range of I/O connections is complemented by options for input and output reactors, DC link chokes, harmonic filters, regeneration units and braking modules.

The F800 inverter drives sold with a three-year warranty as standard, but the design life of 10 years (including the capacitors and cooling fans) means that Mitsubishi can negotiate longer warranties on a case-by-case basis. Mitsubishi F800 intelligent drives comply with relevant European EMC Directive standards, and they also meet the necessary safety standards and have marine approvals, TUV, UL, cUL and CE certification. Go to gb3a.mitsubishielectric.com for further information, or follow the link to download a FR-F800 drive brochure (22.5MB).

23 September 2015

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