Automatic thrust control

Thrust-bearing-load meters for protection against excessive loading are available on thrust bearings, and automatic thrust control, which functions by controlling the pressure behind a balancing drum, also is available. 

In this automatic thrust balancing system, the pressure behind the compressor wheel is controlled to a value between the compressor suction pressure and the wheel peripheral pressure. As the expander inlet pressure increases above the compressor suction pressure level, the resulting thrust force pushes the compressor wheel, and hence the rotor system, towards the compressor suction. In the reverse situation, when the pressure behind the compressor wheel is reduced below the wheel peripheral pressure level, the rotor system moves toward the expander. 

This part considers reactive power control with the use of shunt and series capacitors. The controls may be manual or automatic through electromagnetic or static devices. Protection of capacitors and capacitor banks as well as design, manufacturing and test requirements, installation and maintenance are also covered, the main thrust being on the application of power capacitors. 

A first notch of 250 micrometers radius at the tip was mill cut with a rotary cutter. In order to prevent heating while machining, specimens were cooled with fresh compressed air during cutting. A sharp notch was further introduced at the tip of the first notch with a razor blade. The displacement of the razor blade was controlled by a micrometric thrust so that slow and careful control of the blade advance could be monitored. Figure 3 shows the device used to machine the sharp notches automatically in order to improve reproducibility. 

Today, the main thrust in new developments for die presses is in the area of machine data measurement and control. Techniques have become available to accurately measure the parameters during a press cycle which may only last a few hundred milliseconds. Figure 220 is the reproduction of a typical graph obtained on a four-channel oscilloscope showing top and bottom punch press force, top and bottom punch stroke, and ejection force. Based on such information, production machines can be programmed and automatically controlled. Even more sophisticated systems, so-called press simulators, are being developed and introduced. 

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