58 MOTORS AND DRIVES
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In addition, the wheel
utilises patented integral suspension that is injection moulded in the same operation as the hub. The first application for this unit is a power-assisted suitcase, and a powered golf trolley is currently in development. Compared with conventional motor technologies, the Nano Wheel is claimed to offer a more compact, simpler mechanical design, with fewer moving parts and less friction. Products that fold for storage or transit are therefore easier to design, and the energy efficiency and low friction help to maximise battery life. Compact dc motors are
side failure, it protects the control circuits and connected equipment. According to Control Techniques, other dc drives feature a form of isolation that relies on impedance- only isolation, which has limitations. In contrast, the Mentor MP uses novel technology to achieve galvanic isolation without compromising performance or reliability. Each Mentor MP has
also being manufactured in ever-increasing volumes for even smaller applications. These include solar-powered devices, toys and mobile telephone handsets – for the vibration function. Apart from those systems in which the dc motor
Fig. 4. Perm Motor’s PMG 132 disc armature dc motors operate from 24–72V, have a rated power output of 2.2 to 7.2kW and achieve a peak efficiency of 90 per cent or more.
three universal option module slots in which customers can install any combination of the 18 modules available. These economically priced modules are common across Control Techniques’ ac, dc and servo drive ranges, offering functions such as feedback options,
is connected directly to a switched power supply, the motor is only one half of the dc powertrain. Industrial applications and those calling for precise control of speed or torque require a dc drive. Given the increased demand for dc motors, it is not surprising that there have also been developments recently in the field of dc drive technology. One of the companies most active in this area is
Sprint Electric. This company’s 340XRi, 680XRi and 1220XRi dc four-quadrant dc drives, for motors up to 1.8kW (2HP), are compact and energy-efficient, being designed to regenerate energy back into the mains ac supply under braking without the need for intermediate energy storage, resistive dumping or additional power bridges. At the 2008 SPS/IPC/Drives show in Nuremberg,
Germany, Sprint unveiled two- and four-quadrant PLX digital drives with current ratings up to 1650A, which is a major step up from the previous maximum rating of 1050A.
Another dc drive launched at Nuremberg was the
Mentor MP. Control Techniques claims this drive sets a new world standard for excellence in dc motor control, and also that it is the only RoHS-compliant dc systems drive on the market. Control Techniques has a patent (pending) to
protect an innovative aspect of the Mentor MP’s design. Galvanic isolation between power and control is a standard feature in ac drives and, in the case of a power-
expanded I/O and programmable control. Furthermore, the range of optional fieldbus connectivity is extensive, including Profibus-DP, Interbus-S, Devicenet, Canopen and various Ethernet-based protocols such as Modbus TCP/IP, Ethernet/IP and Ethercat. Parker Hannifin’s Parker SSD Drives division has also
introduced new dc drives, such as the Frame 6 version of its DC590+ family. This is much smaller than previous models, with the company claiming that it requires less than 50 per cent of the cabinet space compared with other dc drives of similar current ratings. The DC590+ Frame 6 high-power drive is available in a choice of three current ratings of 1250, 1600 and 1950 A, with voltage ranges from 380 to 690V ac and power ranges from 600 to 900kW (750 to 1250HP). According to Parker SSD Drives, the DC590+
Frame 6 dc drive has been designed to provide optimum reliability and efficiency with a range of features to minimise wear and save energy. For example, cooling fans are only switched on when required and are constantly monitored for rotation, and built-in snubbers ensure reliable operation even in the event of mains disturbance. To improve operational flexibility still further, option
cards enable the new drive to communicate with popular industrial protocols, including Ethernet, Profibus, Controlnet, Devicenet and Canopen. The DC590+ Frame 6 is also supplied with a full set of function blocks dedicated to section control, including winder/unwinder, dancer (tension) control, PID and load control. In some applications this eliminates the need for a separate logic controller. n
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