Figure 1 Chromalox DirectConnect: low voltage vs medium voltage
Chromalox developed and patented the first true medium voltage element rated to a voltage of 7200VAC. Referred to as DirectConnect (see Figure 1 ), these medium voltage electric heating elements provide a significant advantage over conventional electric designs and bridge the gap from electric technology to fuel fired technology for steam generation and process heating. Benefits of electric heating technology To appreciate the value of electric resistance steam generation over fuel fired steam generation, it is important to understand the benefits of medium voltage electric technology compared to conventional low voltage solutions. Firstly, no intermediate transformer is required to drop down a site’s voltage into the lower voltage realm traditionally required by electric heaters. Even if low voltage were available, these systems would generally draw significant power, such that upgrades to the power infrastructure may still be needed. Beyond this aspect, the value of a medium voltage system is largely derived from the substantial decrease in the system’s amperage due to the higher voltage level. Using the reference of a 4160V system compared to
a 480V system, the associated amp draw is reduced almost nine times. This significantly reduces the amount of wiring, conduit, fusing and contactors required to support the system. Fewer components also mean less time to install, fewer parts to maintain and support, and less risk of failure. Beyond reducing the physical components required with medium voltage systems, a further advantage is gained through improved operational efficiencies. Electric systems, regardless of voltage level, are 100% efficient at converting applied energy into heat. In other words, all energy that reaches the heater is converted into heat and driven into the process. Electric systems do, however, have some losses upstream from the heater by means of I 2 R losses through the power wiring and heat dissipation through the power control components. Even in low voltage systems, these attributed losses are relatively small and only account for approximately a 4% reduction in efficiencies. With medium voltage systems, the reduction in amp draw means less wiring and fewer power-control components, which in turn means fewer losses, resulting in nearly 99% operational efficiency.
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