Wednesday, 6 July 2016

Industrial Automation in India | PLC SCADA DCS Training in Chennai

Adjustable-speed drive : 

Basic electric motor drive alternatives : 

n={120\times {f} \over {p}}

where n is synchronous speed in RPM, f is frequency in Hertz and p is number of poles.  The number of such fixed-speed-operation speeds is constrained by cost as number of pole pairs increases. If many different speeds or continuously variable speeds are required, other methods are required.  Direct-current motors allow for changes of speed by adjusting the shunt field current. Another way of changing speed of a direct current motor is to change the voltage applied to the armature.  An adjustable speed drive might consist of an electric motor and controller that is used to adjust the motor's operating speed. The combination of a constant-speed motor and a continuously adjustable mechanical speed-changing device might also be called an adjustable speed drive. Power electronics based variable frequency drives are rapidly making older technology redundant.