May 2023 Volume 5

ENERGY

Conclusions Electricity costs are a significant portion of operating expenses. An electrical energy survey will determine the energy consumption and cost of an individual piece of equipment. A survey does this by measuring machine power independently of the rest of the plant. The piece cost is calculated by applying the energy cost to production data. This provides production pricing information where the aggregate nature of the utility bill would have otherwise obscured it. The electrical utility pricing structures are weighted towards demand-based charges. Above-average electrical demand will disproportionately increase operating expenses, dramatically influencing the final cost per unit. Energy use is a hot topic as utilities raise their prices. Induction heating has widely variable efficiency and in some instances may be improved through analysis and planning. In the second part of this two-part article, we will look at the varied ways that a forging producer may affect efficiency through changes to production processes and workflow.

Chart 2: Demand charges significantly affect electricity costs So then, it is practically observed that high-demand loads such as motor starting, or high IH power settings significantly increase utility costs. By mitigating high intermittent loads, the energy cost can decrease considerably. SystemEfficiency What affects efficiency? Can any parameter be adjusted to improve it? A partial list of the factors affecting induction heating efficiency includes: • Material resistivity • Stock diameter • Final temperature • Coil fill ratio • Coil design • IH power supply topology/design The most significant loss of electrical efficiency is from: • Ohmic (joule) heating in the induction coils • Billet heat loss through radiation and convection • Poor electromagnetic coupling between the coil and billet, which results in further coil/capacitor ohmic heating The pounds-per-kilowatt efficiency of 6.01 lbs./kW is a friendly outcome considering this is the approximate efficiency number communicated by several induction OEMs. The fact that it equates to an energy loss of 36% is still somewhat cringeworthy, to borrow a modern expression, but that is just how the entropy goes. One incidental result of the efficiency survey is finding the efficiency of the induction heating power supply. In this case, the power supply (coils not included) had a measured efficiency of 92.3%. The power supply losses are from heat generated in the inductors, semiconductors, and capacitors. In the case of a 2,000 kW unit, the 7.7% loss equals 154 kW. Lastly is the loss of efficiency through the manufacturing process itself. Total production efficiency depends partly on the machine's electrical efficiency and partly on production methods. Part two of this study will look at these in greater detail.

Josh Carney is president of Integral Power Technologies LLC, a company that services induction heating equipment for the forging and the other metals industries. IPT also provides consultation services for electrical power quality problems, load measurement, demand monitoring, and efficiency improvements. Josh Carney Integral Power Technologies LLC Phone: 440-701-6022 www.ipt-tech.com

Bibliography [1] C. P. Power, "Billing Rate Schedule," Cleveland Public Power, [Online]. Available: https://www.cpp.org/info/Pricing/Rate-Schedule. [Accessed 15 March 2023].

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