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New 'Two-Wire' Drive Control Card from PAPST Provides Full Control of Three-Phase Brushless DC Motors with Integrated Drive Electronics

PAPST latest brushless "Variodrive Compact" 50W DC motors combine a 50 W power output with built-in drive electronics in a very compact motor measuring only 63mm long x 68mm diameter. And to enhance their versatility even further, the company announces a new '2-wire interface' card that gives users full control over the speed and direction while preserving simple 2-wire operation.

Normally, only very small motors with ratings to a few Watts are available with internal electronics - larger motors have required a separate drive card. However motors with internal drive electronics are normally 2-wire types (the only input is a DC voltage) which means the user has no access to the drive electronics to allow motor speed or direction to be optimised for the application.

The new 'two-wire' card from PAPST is designed to overcome this problem. It plugs directly onto the internal PCB of Papst's "VARIODRIVE Compact" motors. The card carries a multi-turn potentiometer giving users full control over motor speed from 300 to 6800 rpm for the standard 80mNm motor, or 300 to 3500 rpm for the optional 130mNm "gearbox" model. The card also carries two small switches to define the direction of rotation. The card simply requires a nominal 2-wire 24 volt DC supply (hence the term 2-wire card). In this way, all the benefits of three-phase brushless DC motor control are provided with a simple two-wire connection. The card also provides a true-speed output signal from the motor for development or control purposes.

The card can be used in various ways. Small OEM's can use it to determine the exact speed and direction requirements of their application; in production, the direction switches would be replaced with wired-in links and the speed control potentiometer with two resistors. This results in a low cost, rapid means of achieving customisation of a standard motor without the extra costs of factory modification or the often long process of obtaining special samples for evaluation.

Alternatively, larger OEM's can use the card during initial trials to establish the optimum motor performance. Production versions of "their" motor would provide the performance defined during these trials with speed and direction set by software at the factory and the customer would be presented with a complete two-wire (without the conversion card) motor giving just the performance required.

Finally, the 2-wire card can be integrated into the user's control system to provide full dynamic control of the motor whenever required.

The "Variodrive Compact" DC motors, designated types 937 5414 600 and 937 5414 610, are described in PAPST's 80 page DC Motion catalogue and, together with all PAPST fan and motor products on the company web site.

PAPST is one of the world's largest manufacturers of small motors for precision applications as well as fans for equipment cooling. The company pioneered external rotor motors, electronic commutation and more recently intelligent thermal management cooling systems. PAPST plc is part of the worldwide PAPST operation and is located in a modern facility in Andover, Hants with full customer sales and technical support services for motors and fans including systems design, thermal design as well as test and assembly services.