Application Story

Moeller Displays Cool Drives

[picture of Optidrive-controlled Fridge] With the introduction of the Climate Change Levy last year, industry has every incentive to become energy efficient. However, help is at hand from automation and switchgear specialists, Moeller Electric.

Just to demonstrate its prowess in this field, the company has set-up an innovative display at Drives & Controls Exhibition 2002, showing its Optidrive range saving energy and money driving an industrial fridge – live on screen.

Phil George, Moeller's OEM Applications Specialist commented: "The display shows not only how our drives can save energy, but also our ability to deliver a totally integrated automation solution. The drives are connected to a complete network comprising I/O communication modules, PLC and an advanced human machine interface providing a flavour of Moeller's in house expertise in automation."

On the stand is a 2,700-litre fridge with a 3kW cooling capacity powered by a 1kW compressor and two condenser motors rated at 125W each. Driving the system are two of Moeller's extensive Optidrive range, with single-phase input and three-phase output. The two drives together set the optimum efficient running of the motors while maintaining the correct temperature range of the fridge which is set at 0°C to 2°C.

As an example of how the system runs, when the temperature in the fridge reaches 2°C, this signals the drives to start up the compressor and condenser motors via their individual PID control loops. But the beauty of this system is that the motors don't need to work flat out as in a conventional refrigerator. Sensor inputs of the compressor's suction pressure allows the Optidrive, programmed at 3.5bar suction pressure, to maintain optimum compressor running by varying the speed of the motor. For example, if this pressure drops below the set pressure the motor increases speed, while if it rises above the set level the motor slows down and/or stops. Similarly, for the condenser motors, condenser pressure inputs with the Optidrive set at 18bar condensing pressure, ensure optimum running speed.

One of the most exciting features of the display is that through Moeller's automation technology the energy in kW used by the compressor, the condensers, their combined energy, and the energy saving over conventional continuous motor operation is displayed in real time. This is facilitated by Moeller's XI/ON I/O communication modules, which feed information from the drives via a Profibus network to a Moeller PS4-341 MMI PLC. Connected to the PLC is Moeller's MV4-690-TA2 human machine interface, where the comprehensive suite of energy consumption and saving data is displayed on its 15" colour TFT screen. At any one time, from the interface the system can be switched to run on normal continuous operation or via the variable speed drives. The powerful display is also able to represent the information graphically in real time.

Moeller's Optidrive series is not only one of the industry's smallest most powerful AC drives in its class but also by far the most user-friendly. Spanning a 0.37kW to 160kW power range, Optidrive is available in both single and three-phase formats in five case sizes, providing users with the highest levels of performance and flexibility at market competitive prices. The units qualify for an Enhanced Capital Allowance under the Climate Change Levy.

Ready-to-run, the new drives have three programmable digital inputs, an analogue input that is selectable for current or voltage signal, a programmable relay output, and a programmable analogue output. All that is needed for basic pump and fan operation is the setting of five basic parameters from the 14 standard that are available. Optidrive has four pre-set speeds and an auto start function. Other features include skip frequencies, spinning start, silent running in 32kHz mode and mains dip ridethrough.

Drive parameters can be modified via the unit's five-button front panel or using the unique and innovative Optiwand. This is a handheld remote control unit that employs infrared technology to communicate with the drive and/or a PC. The Optiwand has the same five-button layout as the drive and can store up to 63 complete Optidrive settings, using an English language text menu.

Everything that can be done via the drive front-panel can also be done via the Optiwand, then subsequently 'downloaded' to the Optidrive. This greatly simplifies changing the drive settings once the drive is in situ, given that drives can often be located in cramped not easily accessible places. For example: parameters can be downloaded from the drive to the Optiwand, modified, 'reloaded' to the drive and also sent to a PC for reference, archiving, or further modification. The drive package comes with full PC software support.

Using Optiwand, several drives with the same set-up can be very quickly configured, it taking less than 0.5s to transfer the parameters from the handheld unit to each drive. The Optiwand can also be used to quickly monitor individual parameters and, if necessary, instantly change them, e.g. the drive speed. Both the Optidrive and the Optiwand have a very high level of data integrity.

This page last updated: 12 July 2002