Criteria for choosing the right type of voltage regulator

Number of phases

The number of phases of a stabiliser depends on the type of load:

*single-phase load:single-phase stabiliser,

• combination of several single phase loads on the same line: three-phase stabiliser or a single-phase stabiliser on each load;
• three-phase load: three phase stabiliser.

Rated voltage

Due to the fact that the nominal voltage vanes internationally,establish the rated voltage required at the stabiliser input and output.In case of threephase systems, provide with the line-to-line voltage value. The standard voltage stabiliser can operate with nominal voltage 380V-400V-415V(50Hz) or 440V-460V-480V(60Hz).

Input variation range

It's key information for the choice and the design of the stabiliser.Establish the amplitude of the oscillation of the input voltage and always keep a safety margin on such percentage:for example, if the measured fluctuation is ±16%, then choose a stabiliser surtable for ±20% variation. Note:if the input vanation exceeds the nominal one, the difference is added to the output precision. For example.if a stabiliser designed for ±15% input variation receives a +20%voltage, the output precision shall not be ±0.5% but ±5.5%.

Type of regulation

The three-phase voltage stabilisers perform an independent regulation on each phase. The connection to the distributing line neutral wire is mandatory. Should the neutral wire not be available, a specific accessory component must be added.

Type of technology

In most applications,the electromechanical voltage stabiliser is a reliable and safe tool. In case of high regulation speed is required (milliseconds), it is better to choose the solution with regulation by means of IGBT static switches.

Rated power

All the stabiisers are designed for the maximum input current, but itis advisable to consider an extra safety margin for pcssble future expansions. In a voltage stabiliser,the power is expressed in kVA, whilst the load power is usually expressed in kW. Remember that the link between these two measuring units is provided by the power factor (cos p):kVA=kW/cos p.

Also,remember that if the power factor and/or the load power in kW cannot be easily established.measure the absorbed currents in order to allow for a correct design of the stabiliser and keeping in mind that:

-KVA (1-ph.) = load voltage x load curent.

kVA(3-ph.)= root of 3 x phase to phase load voltage x load current.

Installation

Choose the other charactenstics of the stabiliser considering the installation conditions.The following aspect must be known:

• IP protection degree required.

Indoor or outdoor installation.

Site altrtude and ciimatic characteristcs.

• Ambient temperature.
• Possible environmental hazards such as aggressive atmosphere,exposure to chemical components and so on.

Accessories

A standard voltage stabiliser can be ennched with a number of accessonies:

Interruption and protection devices.

• Load protection against over/undervoitage.

Bypass line.

• Input isolating transformer.
• Total protection kit.
• Surge arrestor (SPD).
• Integrated automatic power factor correction system
• EMI/RFI fiter
• Neutral pornt reactor.
• Up to IP54/55 protection degree for both indoor and outdoor installation.

Special construction

By means of some modifications,it is possible to obtain special stabisers able to:

• deal with asymmetrical input voltage vanation different trom the standand range lfor example.from-55%+20% of the nominal voltage).
• deliver an cutput voltage different from the input one for example.Vin+400V±15%,Vout*