Today, electricity is one of the main raw materials used by industry and by the retail world.
The energy produced in power stations is distributed to consumers through the transmission and distribution networks. The quality of the electricity, universally defined as power quality, is one of the factors that determine the economic efficiency both of the consumer systems and electrical networks.
Electrical equipment is designed to function in power supply systems characterised by rated voltage values (e.g. 400V) and frequency values (e.g. 50Hz).
In reality, the distribution of electricity can be such that it does not ensure the stability of these parameters. In particular, the supply voltage may undergo variations, even significant ones, compared to the rated value that may cause undesired situations that are potentially very damaging for users.
These voltage variations may be “fast” and end in just a few milliseconds (for example, as a result of lightning hitting the lines) or “slow”, lasting several seconds, minutes, or even hours, depending on the cause. The “slow” variations may be caused both by rises (poor MV regulation by the power distributor, detachment of large loads from the mains, output overvoltage from generators, etc.) and, more frequently, by drops (connection of large loads, starting up of motors, undersized power lines, ground faults, poor regulation of MT voltage).
The stabilizer is the solution that ensures the best cost/benefit ratio for voltage variations. The continuous availability of stably supplied voltage, independent of input fluctuations, is the key for ensuring efficiency and reliability for the final user.
Reduced productivity, data loss, security loss, equipment failures, inaccurate information and domestic disturbances are just some examples of potential issues caused by unstable supply. All this translates into an increase in management costs for the user.
The voltage stabiliser is an effective solution for preventing potentially damaging situations caused by input voltage instability.
Typical plant situations where the voltage can undergo fluctuations beyond the allowed values include:
Compared with other types of equipment, the voltage stabiliser has a series of advantages that often make it the optimal solution. The cost is generally lower and provides the following benefits:
The voltage stabilizer operates without the aid of batteries and, therefore, does not have storage, transport, maintenance, and disposal issues. The gradual and reliable regulation of the supply voltage to loads ensures, at output, a precision of ±0.5% of the rated voltage, including when faced with significant variations in the input voltage.
The voltage stabilizers are simple to use, have a very high yield, are small in size, and have a reduced sensitivity to inrush currents.
Number of phases
The number of phases of a stabiliser depends on the nature of the loads:
Rated voltage
Since, internationally, rated voltages vary, it is important to measure the input and output rated voltages of the stabilizer. In three-phase systems, provide the concatenated value of the voltages. The standard three-phase models can operate with a rated voltage of 380V-400V-415V (50Hz) or 440V-460V-480V (60Hz).
Input variation amplitude
This is a key piece of data for choosing and sizing the stabilizer. The amount of input voltage oscillation needs to be identified, keeping a safety margin on this percentage. If, for example, voltage variations of ±16% on the rated voltage are measured, a stabilizer sized for ±20% variations should be chosen. Attention to the following rule: if the input variation exceeds the pre-established one, the difference in excess is added to the output precision. For example, if a stabilizer sized for ±15% receives a variation of +20%, the precision of the output voltage will no longer be ±0.5% but ±5.5%.
Type of adjustment
The standard three-phase voltage stabilisers are produced with independent phase control. The stabilizer must be connected to the neutral of the power line. In the absence of a line neutral, it is possible, upon request, to equip the machine with a special accessory.
Technology
In the majority of applications, the electro-mechanical voltage stabiliser is a reliable and safe tool. If high intervention speed is requested (in the order of milliseconds), it is better to choose the solution with adjustment via IGBT static circuit breakers.
Rated power
All the stabilisers are sized for the maximum input current. We advise, in any case, to keep a safety margin for any future increases. The power of the stabiliser is expressed in kVA, while the power of the load is normally expressed in kW.
Please take into account that the link between these two measurement units is provided by the power factor (cosφ): kVA = kW / cos φ.
If the power factor and/or the kW power are not easy to determine, measure the absorbed currents and, taking into account the following formulas, correctly size the stabiliser.
The additional features of the stabiliser can be defined based on the type of installation.
In particular, the following factors need to be taken into account:
It is possible to enhance the stabiliser with different types of accessories:
Thanks to solution customisation, through suitable variants, it is possible to obtain “special” stabilisers capable of:
