Control Sets – Helmke Solutions For Variable Speed Drives Since 1930
The auxiliary machines are typically equipped with commutators, similar to today’s DC motors, and can be either mechanically coupled or uncoupled from the main induction machine. The commutator and/or the commutator bridge of the auxiliary machine can be set to a specific angle or speed of rotation by another auxiliary motor. Based on such electromechanical principles, it is possible to control the phase angle and frequency of the rotor winding currents of the main induction machine, and eventually to inherit characteristics from the auxiliary machines to the main induction machine.
Cascaded systems of main and auxiliary machines, of various designs, can be found in the technical literature. As the chief engineers of the time engaged in a race to push application limits, classic gems of human ingenuity emerged, engineering works that stood out not only for surpassing technical limits (e.g. by pushing the maximum power of a variable speed drive of the time) but also for the associated intellectual heights reached.
Classic examples from this era of engineering are the Leblanc and Krämer control sets, both of which enabled stepless (continuous) power factor and speed control. Modified Krämer systems would later achieve such control and also limit the starting current of the main motor by using only standard DC and synchronous machines as the auxiliary machines of the cascaded system, in contrast to the specially designed armature windings and commutators for the auxiliary machines of earlier systems. The use of standard machines as auxiliary machines of the control sets further accelerated the increase of their power output and the improvement of the overall system reliability.
HISTORICAL AND MODERN REFERENCES OF HELMKE
From the 1930s to the 1950s, J. HELMKE and Co. has developed and produced control sets and contributed significantly to the establishment of variable speed industrial applications. Systems were supplied to German industrial customers. Figure 1 illustrates one of the most complex control sets designed and manufactured to drive extrusion machines for a major German automotive parts manufacturer.
Such references serve today as a rare reminder of the technical heritage, carried on by the HELMKE group. Our senior engineers would probably be interested in even offering you such solutions again, …but they could (and will) stumble against our expert technical sales teams and soon against themselves.
State-of-the-art variable speed drives of HELMKE for the 21st century (figure 2), complete power drive systems consisting of static power electronic converters, converter transformers, motors and all peripherals can be configured to meet specific customer requirements and are available from stock for strategic ranges.
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