For instance highly protected cabinets and IP65 kind of protections are enough to meet most of the environmental requirements. By and large today in Indian conditions the drives are being used as a normal device based on application requirements rather than a protected delicate device. Few years ago the situation was quite different. AC drives had a cosy life inside an air-conditioned place whereas today, in many places, it will be installed in open-air condition, which itself shows the reliability factor.
Some of the applications like air compressors use the conventional drive motor which has no rotation speed adjustment function, generally adopting the cylinders upper and lower limit pressure inspection to start and stop motor or assemble the clutch to obtain the relative constant pressure control. The weakness is that the motor has six times start current, which generates the inrush to the grid and mechanical load. This energy is wasted when the motor is idle. The small pressure range of upper or lower limit will cause the incessant start-stop, which may burn the motor and start the MCC; too broad pressure setting range will cause the pipeline high pressure, high convey consuming, air leakage and pipeline leakage etc. The large air pressure fluctuations cannot meet the requirement of the modern processing technology.
The following effects will be obtained by adopting AC variable speed drives:
- Electricity fee saved up to 20 per cent, the investment returns may be within a year
- Soft start function; no start shock current in the drive motor
- Constant pressure control without the problem of pressure fluctuations
- Pressure sensor input and built in PID functions can realise the constant control (PID facilities are available on selected drives)
- Pipeline fault (block or breakage) detection
- Permit application in constant pressure air supply system driven by multi-motors
- Prolong the running span of the electric switch components and mechanic drive systems
- Reduce the capacity requirement of the power and improve the power factor of the electricity supply and setting equipment
- Constant pressure control, reduce the convey consuming of the airs pipeline
- Provide the air pressure of the stepless adjustments according to the producing process
AC variable speed drives are ideal solutions for most of the industrial applications and especially automation. However, drive manufacturers should continuously bring out the best and latest technology like drives integrated with geared motors, drives with in built programmable logic controllers and so on.
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