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BE Stabilisers

BE Stablilisers

Solid State AC Voltage Stabilisers & Power Conditioners

The BE range offers the advantage of true solid state, low distortion, inductive power control.

Based on the original patented Watford twin tranductor design, providing the reliability of solid state control without the use of power semiconductors in the supply lines which can be easily damaged by voltage spikes or current surges, as is the case with solid state tap changers.

A twin transductor inductor forms a potential divider across two taps of an input autotransformer, one side of which is connected to the load and the other to the incoming mains supply. A solid-state amplifier continuously monitors the output voltage across the load and this is compared against a highly stable reference voltage. Any error is amplified and directly coupled to the isolated control windings on the transductors, thus altering the voltage across the load and reducing the error to zero. The transductors are not susceptible to damage from short circuits or voltage surges and the amplifier operates at a low voltage and current levels.

Over two hundred models span ratings from 0.36kVA to 720kVA output ratings, single or three phase, incorporating full transient spike and noise suppression fitted as standard.

Output voltage accuracy: ± 0.5% accuracy maintained over the full range of input voltage variations from zero to full load irrespective of frequency variations and ambient temperature changes from –5 Deg C to +45 Deg C. Three phase stabilisers will also maintain the accuracy of each phase, line to neutral, even if the input voltage and load are unbalanced. Line to line voltages are fully stabilised when the load is balanced. With an unbalanced load up to 10% the output voltage (line to line) will be within 2%.

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Key Features

  • Fast response


  • Efficiency better than 94% with up to 96% on higher models


  • Waveform distortion less than 2.5%


  • Frequency 47 to 65Hz


  • Full Transverse spike / interference suppression fitted as standard.


  • Common Mode spike / interference suppression optional.


  • Stabilised Output Voltage Can be preset to any value within these ranges

    • H Models L models
    200 to 254 V single phase 100 to 127 V single phase
    346 to 440 V three phase 173 to 220 V three phase

  • Power Factor, any PF lagging to 0.95 leading. Above 65% of full load there is a slight shift in the input voltage range as the power factor deviates from unity. This shift does not exceed 3% for R20 models and 5% for R30 models. The output voltage accuracy remains unaffected.


  • Surge rating ten times the rated current up to 2 seconds. Five times up to 30 seconds. Twice up to 300 seconds.


  • Environment the quoted current ratings apply to ambient temperatures from -5 Deg C to +45 Deg C. Derate by 2% per each additional degree C up to 70 Deg C. Temperature stability better than 0.03% per degree C. Maximum altitude 1000m. Derate by 2.5% for each additional 500m, EM stabilisers are suitable for indoor tropical use.


  • Audible noise level less than 40dB at 1m distance.


  • Spike Suppression. Metal oxide transient voltage suppression is fitted as standard, plus additional protection is provided to attenuate spikes and noise down to harmless levels.


  • Lightning Arrestors. Can be provided to protect the stabiliser and the load form the harmful effects of induced lightning strikes to the incoming supply distribution network.


  • Construction, the larger stabilisers are enclosed in robust floor standing cubicles, with door access for easy installation and servicing. The smaller single phase models are suitable for floor or bench mounting, Enclosures to IP20 BS5490/IEC529


  • CE Conformity Conforms to the requirements of council directive 89/336/EEC EMC (Valid to Oct 2009) & 2004/108 EEC emissions / immunity and directive 2006/95/EC , (Formally 73.23.EEC) Low voltage directive.


  • Correction Time varies according to the model size, typically 3 cycles (0.06 secs) for smaller models and 15 cycles (0.3 secs) for the larger ones.


  • Three Phase models are normally supplied for "star" connection and require an incoming neutral. If no neutral available a static balancer can be fitted to provide an artificial neutral.


  • Quality Management System. Assessed and approved to ISO 9001:2000


  • Environmental Management Policy. Assessed and approved to ISO 14001:2004



© Copyright 2009. Watford Control Instruments Ltd.