IEE Power Engineer, vol.19, no.3, pp.36-39, 2005 (SCI-Expanded)
The use of programmable logic controllers (PLC) to improve power control within induction steel heating furnaces (ISHF) is discussed. Modern PLCs are modular, affordable, have large memory capacities and special functions such as pulse wave modulation (PWM) and data communication. Using a PLC eases position, temperature, and pressure control within the ISHF, and also provides over-voltage and over-current protection. A new PLC control system design also allows heating to take place at constant power while maintaining a steady resonance frequency.