Regulator's role
July 1st 2009

Faced with increasing energy costs and pressure to demonstrate green credentials, organisations are looking at ways to reduce power consumption. Claude Lyons believes its ESS Energy Saving Regulator range offers a solution

ESS insulates users from excessive mains supply dips, and its tightly phase balanced output can prevent equipment overheating and reduce maintenance costs.

Regulators reduce the electrical energy consumed on a site by reducing and stabilising its input supply voltage. The National Grid's standard UK voltage is typically 240V or higher, while equipment made for the EU market is specified for 230V or even 220V. Although the National Grid voltage is within equipment voltage tolerance limits it is unnecessarily high. This creates unnecessary energy losses, extra heating and stress in electrical equipment. So voltage regulation has a role to play in reducing the mains input voltage from 240 to 220V or, depending on the load, 210V.

A report by economic consultancy NERA for E-On stated that the UK could soon face power shortages. Closure of uneconomic plants and low investment could lead to electricity shortages in a severe winter.

Energy generators may reduce voltage levels during peak demand periods to reduce consumption. This should be allowed for within any energy management strategy.

With Claude Lyons' energy saving regulators, the regulator output is user-set to a site's optimum voltage level. A servo amplifier uses the difference between actual and desired output voltage to drive a motorised variable transformer. This applies a variable voltage to the primary winding of a buck transformer which in turn controls the voltage in the secondary winding. The secondary is in series with the mains supply and the load, which enjoys a stable supply regulated to within typically ±1% of its setpoint level. This provides a fast, smooth, stepless and harmonic free response, which is typically 99% efficient.

Real example Figs 1 and 2 shows an energy saving regulator performing better than a fixed ratio step down transformer. In both cases, the objective was to ensure that the supply to the site did not dip much below 220V, making adequate allowance for voltage drops across the site. To achieve this, the transformer output must average over 228V; while the voltage regulator's tightly controlled regulation allows an average of 220V without risk of unacceptably low voltage excursions at the user equipment inputs.Whereas the transformer yields an energy saving of 8.7%, the voltage regulator achieves 14.9%. On some sites, depending on wiring and load conditions, larger voltage reductions and energy savings of up to 25% may be possible.

With all three phases maintained to within ±1% of their target level, ESS output is always phase balanced. This is important for some loads where unbalanced phases cause equipment overheating and reduced service life. Should the mains voltage unexpectedly drop for any reason, the regulator will maintain its controlled output, shielding the onsite load from external events. By contrast, a fixed ratio transformer output drops proportionally to the input voltage, even if this takes the load voltage below acceptable operating levels.

However, not all loads benefit from voltage optimisation. Examples include computers, communications systems and other IT hardware using switched mode power supplies, variable speed inverter drives, lighting with high frequency ballasts and thermostatically controlled items such as an oven. A site survey that includes an estimate of savings (before investing in voltage optimisation equipment) is essential.

Energy savings can typically be expected to reach 5 to 15%, with values up to 25% sometimes achievable. Add to this the savings arising from longer equipment lifetime and reduced maintenance. Payback is usually 12 - 36 months. Reduction in carbon footprint can also be significant, as each kWh saved equates to on average 0.43kg of CO2. The Carbon Trust offers interest free loans to buy ESS products. As these are repayable over up to four years, they are often covered by the energy savings; the regulators have essentially cost nothing to install.

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