DRIVE SYSTEMS LIMITED is a wholly owned independent company which was founded in 1986 by its present directors, both of whom had extensive experience of variable speed electrical drives in industrial applications, to promote the use of the inverter and its associated control equipment into areas where positive advantages could be achieved, whether in production efficiency, improved product quality or reduced costs. This has involved the company working for a wide variety of industries, from nuclear to water and from woodworking to pet food. The common factor is, of course, the ordinary three phase AC motor which, while being commendably tough and resilient, is not renowned for its versatility of control when fed from the standard mains supply An inverter fed motor can be a totally different proposition with accurate control of speed, torque and even shaft position being possible. With recent developments it is now feasible to use an AC motor and drive combination in practically any application, even those traditionally considered only suitable for DC motors.
Energy saving by operation of a motor and its load at a speed lower than the possible maximum is one specific area which continues to be very popular, with capital payback periods of under 12 months being feasible. Pumps being controlled with throttling valves and fans with damper control are the most fertile areas from which energy savings can be reaped. Experience shows that all systems employing these crude control techniques give excellent results when modernised. A most dramatic illustration of the massive savings potential available was produced when an inverter was recently fitted onto a cooling pump on an aluminium rolling line. Full pump output was required only when rolling was in progress, a period of 1 - 2 hours per day. The pump lost its prime if switched off, however, so short circuit pipe work on the pump output was introduced to allow continuous running. The power consumption when running short circuited was approximately 30 Kw. When an inverter was introduced and the short circuit running speed was controlled to a speed where pump prime was just maintained, power consumption decreased to under 3 Kw.
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