Maximizing Power Utilization
The ideal induction melting system pours the most metal at the lowest level of kilowatt demand. MICHAEL NUTT, INDUCTOTHERM CORP., RANCOCAS, N.J.
consideration when it comes to cut- ting costs. Still, in the large majority of facilities, energy offers the greatest potential for savings when compared to labor, melt loss and maintenance. Te melting department consumes more energy than any other operation, so it is a natural starting point when looking to reduce consumption and minimize demand costs. Te key factors when examining
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production versus demand include efficiency, performance, power supply technology and power utilization, which includes equipment configura- tion and type, operational practices, melt preparation and charging and pouring processes.
nergy consumption in a metalcasting facility’s melt department isn’t the only
Efficiency: In recent years, signifi-
cant improvements have been made in induction power supply efficiency. Today’s solid state power supplies are achieving efficiencies around 98%, which is substantially higher than earlier solid state or hard state technology. Metalcasters should review the efficiency of an exist- ing melt system to see if substantial gains can be achieved via newer technologies. Batch melting, where the furnace is emptied after the metal has reached the proper temperature, is typically 7% more efficient than “heel” melting, where a certain amount of metal is kept in the furnace after melting. Tis difference results from improved coil efficiency during the early stages of the batch melt cycle.
Melt System Performance: To maxi-
mize production for paid demand, the melt system must be able to pull full power throughout the entire melt cycle. True batch melting systems should be designed to pull full power from the initial charge until the target temperature is reached. Some melt systems may not be able to reach full power in the early stage of the melt, meaning consumption lags below the demand level. Power Supply Utilization: Power
supply utilization is the ratio of melt time to the overall total melt cycle time, which includes the melt time and the time required for tasks such as temperature measurements, slag removal, pouring and initial recharging of the furnace. (Tis is also referred to as the off time or hold time portion of
Figs. 1a-1b. The melt system at left (1a) had 22 minutes of downtime and power utilization of 65%, compared to 14 minutes and 81% at right (1b). February 2015 MODERN CASTING | 47
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