Technical Terms

Accuracy

By this we mean the maximum deviation you will get above or below the set output voltage of your stabiliser. Our specification will always quote the accuracy achieved even if all four parameters are affected simultaneously, i.e. a variation over the full input voltage range, change from off load to full load. Plus variations in power factor and mains frequency. In addition three phase stabilisers will maintain the output voltage accuracy even when the input voltages and the output loads are unbalanced.

Surge Rating

The multiple of the maximum current rating the equipment will withstand for a given time, without damage to the stabiliser.

Waveform Distortion

AC Voltage and Current are, unless stated to the contrary, measured in terms of RMS. In a pure sine wave supply, the peak is 1.41 times the RMS value, and the mean value is 0.9 times RMS. The energy dissipated in a resistance will depend on the RMS value. The DC voltage of an AC to DC converter will depend largely on the "Peak Value", and the torque of a motor or the force of a solenoid will be determined by the "Mean" value.

An equipment designer assumes that the electrical supply will be sinusoidal, and rates all parts accordingly. A good mains supply is seldom distorted by more than 1%, and distortion up to 3% is acceptable, It makes little difference whether you measure the voltage of such a supply with a true RMS or "Mean" voltmeter, but the load (especially if it is a switch mode power supply) may draw a very distorted current waveform, and in rating the supply an RMS reading ammeter should always be used. Our sales department will be able to advise you.

Speed of Response

For the Watford Control EM/EMS AC Voltage Stabilisers, we always define response speed in terms of the time taken to reduce a 10% voltage error to within 2%. Other manufactures usually quote the speed of response as "Volts per Second", these show the maximum rate of correction the servo drive can reach, ignoring the time taken to reach full speed and slow down again, and therefore are meaningless.

The faster response of our BE Solid State range is always defined in times of time constant i.e. number of mains cycles and in milliseconds.

Input Voltage Range

This is the total permissible supply voltage variation range within which the stabiliser will maintain its stated output accuracy.
It is expressed in percentage of the preset output voltage, plus and minus, and if this output voltage is reset to a different value, the input voltage range will alter in proportion.

Soft-Start

This option provides extra protection when stabilisers are having to handle wide supply voltage variations. If the stabiliser is switched off when the mains supply is low and switched on when it is high, a momentary over voltage of 50% or more can damage the equipment before the stabiliser has time to correct it. When the soft-start option is fitted the stabiliser will provide a lower output voltage at the moment of switch on which will then smoothly rise to the required output voltage.

AC Power Conditioners

Certain mains powered equipment not only requires as stable supply, maintained within specific limits, but a clean supply that is free from transient spikes and noise. In these cases a Power Conditioner offers the ideal solution by isolating the output voltage and filtering out any noise and interference on the incoming supply.

Transverse Mode (Symmetrical) Interference Suppression

This will suppress any spikes, transients and noise between line and neutral, or line to line. While all our stabilisers are fitted with 'spike clippers' as standard, this extra attenuation will reduce a 7kV 200-microsecond pulse to a harmless ripple. The attenuation is of equal magnitude from off load to full load.

Common Mode (Asymmetrical) Interference Suppression

This will eliminate any potential difference, i.e. spikes, transients or noise developing between earth and neutral, or earth and line. A screened, double wound isolating transformer is connected to the output of the stabiliser, enabling the secondary neutral to be earthed and at that point, the common mode interference is ZERO. A floating secondary is neither desirable nor safe.

EM/EMS and BE series AC Voltage stabilisers can be supplied in 'Power Conditioner ' versions. For more details please contact our technical team.