Ac drives designed for permanent-magnet motors

Paul Boughton
Parker Hannifin is launching a new family of AC drives that enable permanent-magnet motors to be used in a wide range of pump, fan and compressor applications. Designated the AC650S Series, the new drives eliminate the need to run permanent-magnet motors with closed-loop speed sensors, enabling them to be used as replacements for AC induction motors and helping users to improve performance and profitability.
According to Parker, using the AC650S drives to switch from induction to permanent-magnet motors can cut energy consumption by up to 12 per cent while reducing the combined drive and motor space requirement by as much as 75 per cent.
Permanent-magnet motors are not widely used in many industrial applications as they require additional speed or position sensing mechanisms and control by high-end drive units, making them relatively costly and complicated to install. As a result, induction motors have generally been the preferred choice, despite being larger and less efficient.
Now, however, by using innovative algorithm control based on motor voltage and current output, the new AC650S drives enable standard permanent-magnet motors to be used in closed-loop applications without the need for additional sensors. Engineers can therefore benefit from the energy savings that can be achieved from brushless motor such as Parker's NX and Atex EX Series, with savings of up to 12 per cent for a 0.75kW system being possible; similarly, engineers have the opportunity to design more compact control systems, which can be as small as 25 per cent the size of a conventional induction motor assembly.
Product features
The new AC650S drives provide high start-up torque, without the need for additional tuning, and offer a range of features to make them quick and simple to setup and install. For example, each drive is supplied with free software configuration tools, with pre-set macros for many common applications, and requires just a few motor parameters to be input during commissioning. Additionally, the AC650S has front panel-mounted LCD and input controls, with simple diagnostics, integrated EMC filters and analogue and digital I/O, including RS232 programming ports. The new drive can also be supplied with optional Profibus-DP and Modbus RTU interfaces, while a cloning module is available to enable up to ten drive configurations to be stored for ease of maintenance.
Parker offers the AC650S family of drives in three frame sizes, covering single- and three-phase applications, from 0.25-7.5kW and output frequencies from 0-500Hz.
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