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Liquid-cooled servomotors `triple the power density`

21 November, 2011

SEM, one of a handful of British exhibitors at this year’s SPS/IPC/Drives show in Germany, has used the event to launch new ranges of liquid-cooled servomotors and asynchronous spindle motors, as well as extending its range of AC servomotors with a high-power, high-torque model.

The Kent-based company says that its new HW series liquid-cooled servomotors (above) deliver more than twice the power of standard servomotors, as well as offering improved dynamic performance. SEM has added the cooling jacket without any significant increase to the size of the motor housing, while increasing the stall torque on 190 frame models to 134Nm and the output power to 29kW. These figures represent nearly a three-fold increase in power density compared to SEM’s standard air-cooled servomotors with the same flange size.

“In developing these liquid-cooled servomotors we have addressed a number of issues that were being raised by customers,” says SEM’s sales and marketing manager, Steve Jackson. “In particular, where motors are used in precision applications, such as machine tools, they may wish to limit the heat that the motor generates and, in turn, maintain a steady ambient temperature. This will help to overcome problems associated with temperature fluctuations during operation of machines that may be working to micron tolerances.”

The new range is compatible with SEM’s existing motors and has standard flanges. Users can choose various feedback devices, including resolvers and precision encoders.

The dynamic performance of the motors makes them especially suitable for high-speed positioning and packaging systems, servo pump drives, and punch presses.

The rugged new ASM asynchronous spindle motors (above) provide high performance with low vibration, and offer constant power from their rated speeds up to maximum speeds as high as 18,000 rpm. The motors are available in three frame sizes (200, 260 and 320 mm square) with rated power outputs from 5.5–40kW.

The rugged construction of the motors allows them to be used in harsh environments and in applications where standard squirrel-cage motors would not be suitable. They are fitted with precision encoders from Heidenhain (SEM’s parent), allowing closed-loop vector control.

The four-pole motors can be supplied with hollow or solid shafts and there is a choice of bearing types, including the option of a spindle bearing that allows the motor to withstand greater radial forces and elevated speeds.

SEM has also extended its range of synchronous AC servomotors with the addition of the HJ260 motor, which has a power output of 25kW and a maximum stall torque of up to 250Nm. Combined with high peak torque figures from zero rpm, this results in good dynamic performance. By adding high-specification feedback devices, the motors can be used for high-power, precision applications, such as plastics moulding.

The permanent magnet motors, based on a 260mm square frame size, come in a choice of four lengths. IP67 protection is an option for applications in harsh working environments or where corrosion resistance is important.

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