Electrical switching & drive systems & components


Drives achieve true field orientation without feedback

Second Quarter 2008 Electrical switching & drive systems & components

High-speed stability and accuracy, together with reproducible torque are requirements for motion control in systems manufacturing high-quality products.

From its many years of experience in the development and application of advanced servo systems, German motion control company KEB has developed advanced drive control algorithms which allow it to sense a virtual rotor position within the control software, without requiring an encoder or other feedback sensor on the motor shaft.

The company has developed Combivert F5 sensorless drive solutions for both synchronous (Model SCL) and asynchronous motors (Model ASCL), for applications requiring high speed and torque control. The drives are available in the power range 0,37–900 kW and voltage classes 1/3 phase 230 V, 3 phase 400 V and 3 phase 690 V.

In both versions the current controller provides a load-dependent current supply with high overload capacity, fast correction of load peaks and precise torque control.

Other advantages of these drives include:

* The ability to display speed and torque.

* Reduced costs due to omission of encoder, interface and cable.

* Increased robustness and increased operational reliability, since potential sources of interference from the encoder system are removed.

The SCL version for synchronous motors has been designed for high performance speed and torque control in processes where the system-related advantages of permanent magnet motors can be gained without feedback.

KEB claims that the SCL achieves improved speed stability vs. vector control drives while performing identically to conventional closed loop drives during sudden load variation (See Figure 1). The drive also provides standstill position detection.

Figure 1. The Combivert F5 SCL performs identically to conventional closed loop drives during sudden load variation
Figure 1. The Combivert F5 SCL performs identically to conventional closed loop drives during sudden load variation

The ASCL for asynchronous motors operates with standard drives over a wide power range, for applications requiring consistent speed and torque accuracy. It automatically acquires and models connected motor characteristics to give excellent control. The motor model includes thermal computation.

For more information contact Mike Vernes, Pneumatic Electric Control Systems (PECS), +27 (0)31 303 3701, [email protected], www.pecspower.co.za



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