Page 165 - Industrial Power Engineering and Applications Handbook

Static controls and braking of motors 6/145

accuracy through a feedback network, this technology devices. Therefore they have a very wide application
finds many applications in such process industries as the in mines and other hazardous areas using flameproof
following: a.c. motors where d.c. machines cannot be used.
Textiles
6.17 Speed variation through
Material handling variable-speed fluid couplings
0 Steel rolling
On- and off-shore drilling platforms The speed of the motor can also be varied by a variable-
0 Machine tools speed fluid drive as discussed in Section 8.4.
Process industries such as sugar, printing machinery,
cement mills, chemicals, paper
Thermal power plant auxiliaries such as flow control 6.18 Static drive versus fluid
of primary air fan, ID fan and forced-draught fans, coupling
boiler feed pumps circulating water pumps and
condensate pumps, coal handling plant (e.g. ball mill,
wagon tippler, and stacker reclaimer) Variable-speed drives are essential for many industrial
Mining. A solid-state semiconductor device has no applications requiring variable operating parameters during
physical contacts to make or break the current. There the course of operation. Such variations can be in the
is thus no arc formation during switching of these flow of fluid and pressure of air or gas etc. The con-