1) What is the difference between a step-down transformer with fixed ratio and PQL-ESL?

There are at least two fundamental differences.

  • The step-down transformer reduces the fixed-ratio line voltage, but it is not able to maintain a constant and user-adjustable voltage level to utilities. It simply reproduces the line voltage, reducing it to a fixed ratio.
  • When the line voltage is too low, this solution cannot reach the desired power quality level, but it also may cause any additional problems to the system because of the low-voltage level.

The ESL-PQL require a constant voltage level to the utilities regardless of the voltage level. They are fully reversible and the adjustable voltage control unit injects a positive dV, in order to ensure the correct power quality level to utilities, when the line voltage is too low. The ability to correct the network failures operates in the 330-460V range in ESL, by fixing the utility voltage level at 380V.

This range has been extended to 300-500V in PQL.

Trend chart of voltages applied to a real system with the solution offered by Enersolve.


Trend chart of voltages using the fixed-ratio transformer.

2) What is the difference between a step-down transformer with variable ratio by means of multiple sockets and PQL/ESL?

Even in this case there are at least two differences.

  • The step-down transformer reduces the variable-ratio line voltage, but it is linked only to 3 or 4 unchangeable steps. This serviceability cannot maintain a constant and user-adjustable voltage level to utilities and is not able to bring three-phase output voltages back to the desired value. Therefore any line-voltage unbalances are reproduced in the output voltage, with consequent imbalances in resulting currents.
  • When the line voltage is too low, this solution cannot reach the desired power quality level, but, in the best case scenario, ceases to operate and becomes transparent, returning the same line voltage to loads.

The advantages of Enersolve solutions are those already described at point 1.



This chart represents the trend of voltages measured at the output on a device, as described in the title. With reference to the serviceability of Enersolve solution at least three differences are forthwith noticeable:

  • The voltage has been changed step by step (in this instance, a 15V step and two 7.5V steps), but without continuity.
  • The line voltage unbalance has been reproduced exactly in the voltage supplied to utilities.
  • It is impossible to impose a desired voltage value in the output because of coarse modulation. The modulation capability of Enersolve machines is equal to 1V.

3) There is a transformer cabin supplying medium voltage power (typically 15kV) in many production situations. Is it enough in this case to change the transformer output voltage, using the sockets available on the secondary side?

Even in this case it applies to what described at point 1.

A simple transformer, because of its fixed turns ratio, is not able to maintain the output voltage at a constant, settable and stabilized level. It simply reproduces the output voltage, reducing the line voltage.

However, the fluctuation in line voltage is prescriptively very wide (+/- 10%) and no claim against the supplier is possible under this change.

Reducing to a minimum the voltage of transformer for energy saving can be counterproductive and detrimental to the operation of utilities; when the input voltage (Vp) is at a minimum (Vnom -10%), there is a risk for getting too low voltage (about 340V) on the secondary side (Va) for the proper functioning of the machinery, in particular in situations where the internal distribution lines are very extensive and complex.

In this case it’s always useful to perform a voltage measurement at the furthest point of the system from the transformer cabin.

In this case the advantage offered by Enersolve solutions is that the voltage can be easily adapted to the bare minimum for the operation of utilities, finding the best compromise between the achievement of savings and a better energy consumption.

4) Enersolve solutions can be used as an Uninterruptible Power Supply (UPS)?

The UPS is a static machine, such as ESL/PQL, which is mounted in series on the utility line.

They are AC/DC-DC/AC double conversion machines ensuring the continuity of the utility power line, even in the case of short-lived blackouts, using fully charged batteries.

This is the only advantage compared to Enersolve solutions. But there are at least three important advantages in favour of Enersolve solutions:

  • A significantly lower price, typically with a ratio of 1:5.
  • An expensive and difficult management of battery packs has been avoided.
  • The yield is much higher, allowing to maximize the capacity to generate energy saving.

In this regard, you can appreciate the typical features of an UPS in the picture taken at random from the catalogue of one of the players in the market. The yield ranges between 90 and 93%, making this solution unusable in almost all cases, if you want to achieve energy savings. The typical yield of Enersolve solutions is always higher than 99%.


5) Enersolve solutions are compatible with the systems where self-generation occurs ? Are they nevertheless useful?

The solutions are certainly useful even in these cases for at least three reasons:

  • Although the energy is self-produced, a lower consumption of utilities is in any case an added value which implies, for example, a lower fuel consumption by the generator.
  • All production units are interconnected with the distribution network for law enforcement. The connection is established through interface relays, so that the possibility of generating electrical energy is eliminated, if the network conditions are incompatible with the characteristics of the generator. ESL-PQL are able to mitigate this type of problem, because they are reversible and impose a specific power quality level to the generator.
  •  Any portion of electrical energy which is not intended for utilities can be transferred to the network and invoiced to the network operator.

6) What is the accuracy and calibration class of the on-board metering device?

The class of on-board metering device is 0.2.

Currently Enersolve equipment shall be provided with a Lovato dmg600 multimeter (the product technical specification is available at the Lovato website).

7) Customers would like to receive clarifications on measures …

All data measured by dmg600 is stored and available on Enercloud platform. It is possible to display temporal instants at which the samples occur from the web portal, the values ​​discarded by an algorithm for the calculation of energy saving can be, however, displayed.

Apart from ENERSOLVE web portal, it is possible to download the data also independently by direct connection with on-board Wi-Fi.

Both the ESL and PQL solutions of Enersolve measure and process energy saving data according to an algorithm based on the principles of the ENEA Protocol ESPRO and the IPMVP Protocol (International Protocol of Measurement and Performance Verification).

According to ENEA’s ESPRO protocol, each day is divided into 96 intervals lasting 15 minutes. In each interval a sampling cycle of 30 seconds is performed, during which the operating status of the equipment and the related electrical values are detected.

8) SCHEDULED MAINTENANCE: is a scheduled machine maintenance foreseen in the first two years?

In the absence of a scheduled maintenance contract, interventions by Enersolve staff is neither planned, nor considered necessary. The customer must take care of its own according to best maintenance practices for electrical equipment.

On the contrary, the maintenance program of Enersolve includes control and monitoring interventions of the equipment status since the first year, within 12 months from date of commissioning.