e4+ — amorphous distribution transformers with Ecotap VPD vacuum OLTC up to 3 MVA

Description

e4+ is a version of the e4 amorphous transformer with a built-in vacuum on-load tap changer (OLTC). Regulation is needed where voltage fluctuates, and many sites in the UK are supplied at an elevated voltage, while non-dispatchable renewable generation and large motors make sags and surges worse. Excessive voltage increases consumption and load losses, so keeping it at the required level gives additional savings on top of the low intrinsic losses of the transformer.

The base e4 has an off-circuit tap changer (DETC) with an extended +7.5 % tap and a reduced secondary voltage of 415 V. This is enough if the voltage changes rarely, but switching requires the transformer to be de-energised. The e4+ is equipped with the Ecotap VPD vacuum OLTC, which automatically holds a constant LV voltage without disconnecting the load during random peaks and sags of the supply network.

According to the manufacturer, this is the most compact fast-acting OLTC in the world, with 9 or 17 adjustable positions, an interval of 3 seconds between tap changes and a life of up to 500 000 tap changes without maintenance. This life exceeds the service life of the transformer. According to the OLTC data, the degree of protection is IP30 (with an optional IP54 enclosure) and the operating temperature is from −25 to +70 °C. A separate voltage stabiliser is not needed, so space is saved and its maintenance is eliminated.

The transformer keeps the properties of the e4: an amorphous core, minimum total losses (27 % lower than Tier 2), rating up to 3 MVA, 11 kV / 415 V, oil or ester cooling ONAN or KNAN, standard IEC 60076. Attached panel radiators are used from 1500 kVA, and smaller ratings are made without radiators. Examples of earlier generations with an OLTC are the e3+ at 3 MVA at the Dovecote Park food plant and the e2+ at an ASDA supermarket, where consumption fell by 7 % and savings exceeded 285 000 kWh per year.

Applications are retail chains, the food industry, logistics, and sites with their own renewable generation and unstable voltage. Production is in Leeds (UK) and Chennai (India); the site of over 5500 m² has three production bays by transformer type and size, two test stands and two paint booths, and the engineering team in the UK adapts designs to project requirements.

Technical specifications

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