There is too much said about unpleasant things that can happen with the electric mains to chew over it another time. It’s only worth reminding that there are practically no perfect power mains, in any case, those which can be called unproblematic by default. Any socket is hypothetically dangerous. The only difference is that in some areas failures can happen once a year, and in others they can be so frequent that sensitive hi-tech equipment can’t function at all. The easiest way to protect your devices in such situations is to use automatic voltage regulators. These appliances are relatively cheap, but they have undeniable benefits.

In this article, we offer you to get acquainted with a new SVEN product line. The AVRs in this line have power from 500 to 3000 VA, and the declared technical specifications arouse respect. The new samples look very confident even on the background of NEO R line we have already tested. First, they haven’t gone up in price. Second, to realize the design, a reliable metal case with convenient indicators is used. And finally, third, the declared input voltage range is striking 100-280 V, while the output voltage is to remain within 220 V ±8%. Without pathos, we state the fact that the devices are great, according to their description, that’s why we gladly settle down to more detailed studying.

To make today’s test more illustrative, let’s supply it with comparison elements. That is, except for SVEN AVR-1000 LCD, we’ll examine two more AVRs with similar price and power.

Package Contents

The new series voltage regulator is sold in an ordinary carton box. Inside, there is nothing except a paper operation manual, a warranty card and itself. However, no additional cables are necessary for its operation, as the output is a standard socket and the input cable is embedded into the case.

Appearance and Design

The whole case, except for the front plastic panel, is made of 0.7 mm thick metal. From the point of view of fire safety, it’s the optimal variant, as even non-flammable plastics are not as reliable as metal, especially in emergency situations. On the floor, the device is placed on four plastic legs – other placement variants are not provided.

On the front wall, there is a power switch, an output switch-on delay control button, three LEDs and two digital indicators. It’s worth admitting that the new AVR series is produced with two types of indicators: in our case digital voltmeters are used, and besides, there are virtually identical samples with analogue instruments. Digital indicators are more convenient, as they allow to trace the quality of the supplied power more accurately. By the way, the accuracy of measurements is very high. They differ from a reference device’s in several volts only. The LEDs serve for visualizing the operability of the device and delay mode switch-on.

The delay function is used for delivering power to consumers after its renewal with some pause. When the Delay button is pressed, the pause is 120 seconds long, when it’s not – 6 seconds. Such a function is used to protect some devices against frequent voltage falls. It’s exceedingly important for equipment whose launch time is connected with extra difficulties and peculiarities. For instance, for compressors and electric motors.

The output is made like a separate socket on the rear panel. It’s equipped with grounding contacts and protective shutters. It’s clear that such power capacity is suitable for several consumers, so, if necessary, you’ll have to use any power distribution device. Optimally, it should be equipped with extra protection.

Internal Design

Inside, the AVR is simple and quite interesting. The main regulating element is a transformer on a toroidal core. It’s an unconventional solution if compared to classical transformers with E-shaped cores; however, such a variant is more producible, as it leads to reduction of losses, noise, weight, and so on. The transformer is screwed up to the case through a rubber spacer which minimizes noise and vibration. You won’t hear any humming even in a silent room or at night. The transformer has a temperature detector. It allows to protect the device form overheating in case of overload.

The windings of the transformer are changed over with six Songle SRD-12VDC-SL-C relays. Their contacts are designed for current switching up to 10 A, i.e., maximum power can reach 2.2 kW against 700 W in our case. Such a reserve lets us assume that the contacts won’t burn and stick with time.

The electronic section is mounted on one chip. The quality of the mounting is very high, and the circuitry level is quite simple. To realize all the possibilities, an 8-bit Holtek Semiconductor HT46R064 controller is used, as well as LM324N microchip combining four op amps. The wiring is carefully distributed, so nothing prevents the device from self-ventilating.

Choosing Necessary Nominal Power

Before the practical test we’d like to give some advice on choosing the most suitable model according to the power of the consumer. The figure in the description of our samples – in this case 1000 – shows maximum power in VA (volt-amperes). It corresponds to about 700 W. For reliable operation, we recommend to leave some reserve of at least 10%. To put it simply, maximum long-term consumer power in this case shouldn’t exceed 650 W.

However, it’s not all, as in the case of strong voltage sags an additional decreasing coefficient is applied. Such a relation must be shown briefly in the operation manual. For example, for SVEN AVR-1000 LCD load power mustn’t be more than 85% of the nominal at the input voltage of 150 V, but if the input voltage is 100 V – it shouldn’t exceed 50%. Otherwise, the automatic transformer will overheat. Naturally, this rule is applicable to any other devices. The test will show how significant and dangerous it is.

Practical Test

So, it’s time to check how good the AVRs are in real conditions. To see how accurate the adjustment is, we connect them in turn to a 2 kW lab transformer and measure the relation of output voltage.

In theory, SVEN AVR-1000 LCD must produce 202 - 238 W even at considerable power sags, sometimes reaching 100 W. The result we got exceeded our bravest expectations. Formally, output voltage can reach lower than the fixed mark, but it occurs at critically low input range – 98 -102 W. Most consumers, though, will operate without fail. Altogether, there is very soft adjustment throughout the whole range, when the output voltage doesn’t reach lower than 206 W or higher than 235 W. We can just state that SVEN AVR-1000 LCD is one of the best AVRs our laboratory has ever examined – it provides accurate voltage regulation at the output and can operate at ultralow input characteristics.

Winding Changeover

SVEN AVR-1000 LCD changeover time doesn’t arouse any criticism. At the instant when the windings are switched there are insignificant 2–4 ms long sine shape distortions. In the most negative case we observed the process of normal shape settlement that lasted for 8 ms, but such moments are absolutely safe for any computer equipment, say nothing of more primitive loads.

Conclusion

To sum it up, we can say that two out of three AVRs we have discussed today have made a very good impression. We liked SVEN AVR-1000 LCD due to the complex of factors. It’s an inexpensive, simple and reliable device. The model is produced in a metal case, the transformer windings change over practically instantly, and the output voltage remains normal even if the input characteristics range from 100 to 280 W. One should understand that very few voltage regulators can operate at such low input voltage, and here SVEN AVR-1000 LCD is beyond competition. An important fact is that in normal operating conditions no considerable heating is observed, and this is another plus to reliability and long operation life.