Comparison Konner&Sohnen KS 4500i vs Konner&Sohnen KS 7000

The nominal power of a generator is the highest power that the unit can supply without problems for an unlimited period of time. In the “weakest” models, this figure is < 1 kW, in the most powerful ones – 50–100 kW and even more ; and generators with welding capabilities (see below) usually have a nominal power from 1–2 kW to 8–10 kW.

The main rule of choice in this case is as follows: the nominal power must not be lower than the total power consumption of the entire connected load. Otherwise, the generator will simply not be able to produce enough energy, or will work with overloads. However, to determine the minimum required generator power, it is not enough to simply add up the number of watts indicated in the characteristics of each connected device - the calculation method is somewhat more complicated. Firstly, it should be taken into account that only the active power of various equipment is usually indicated in watts; in addition, many AC electrical appliances consume reactive power ("useless" power consumed by coils and capacitors when working with such power). And the actual load on the generator depends on the total power (active plus reactive), indicated in volt-amperes. There are special coefficients and formulas for its calculation.

The second nuance is related to the power su...pply of devices in which the starting power (and, accordingly, the power consumption at the moment of switching on) is significantly higher than the nominal one - these are mainly devices with electric motors such as vacuum cleaners, refrigerators, air conditioners, power tools, etc. You can determine the starting power by multiplying the standard power by the so-called starting coefficient. For equipment of the same type, it is more or less the same - for example, 1.2 - 1.3 for most power tools, 2 for a microwave oven, 3.5 for an air conditioner, etc.; more detailed data can be found in special sources. Starting load characteristics are necessary primarily to assess the required maximum generator power (see below) - however, this power is not always given in the characteristics, often the manufacturer indicates only the nominal power of the unit. In such cases, when calculating for equipment with a starting coefficient of more than 1, it is worth using the starting power, not the nominal power.

Also note that if there are several sockets, the specific division of the total power between them may be different. This point should be clarified separately - in particular, for specific types of sockets (for more details, see "230 V sockets", "400 V sockets").

The maximum power output that the generator can provide.

This power is slightly higher than the nominal (see above), but the maximum performance mode can only be maintained for a very short time - otherwise an overload occurs. Therefore, the practical meaning of this characteristic is mainly to describe the efficiency of the generator when working with increased starting currents.

Let us recall that some types of electrical appliances consume several times more power (and, accordingly, power) at the moment of starting than in the normal mode; this is typical mainly for devices with electric motors, such as power tools, refrigerators, etc. However, increased power for such equipment is needed only for a short time, normal operation is restored in literally a few seconds. And you can estimate the starting characteristics by multiplying the nominal power by the so-called starting coefficient. For equipment of the same type, it is more or less the same (1.2 - 1.3 for most power tools, 2 for a microwave oven, 3.5 for an air conditioner, etc.); more detailed data is available in special sources.

Ideally, the maximum power of the generator should be no less than the total peak power of the connected load - that is, the starting power of equipment with a starting factor greater than 1 plus the rated power of all other equipment. This will minimize the likelihood of overloads.

The type of alternator provided in the unit.

The alternator is the part of the generator that is directly responsible for generating electricity. Such a system works on the principle of the movement of wires (coils) in a magnetic field, due to which an electric current arises. However, the features of the work of the alternator can be different, on the basis of which they are divided into types: asynchronous , synchronous, inverter and duplexes. Here are the main features of each option:

— Asynchronous. The simplest version of the alternator. The rotor (rotating part) in such models during rotation is somewhat ahead of the movement of the magnetic field created by the stator (fixed part) — hence the name. The practical advantages of asynchronous alternators are simplicity, low cost, good protection from external influences and insensitivity to short circuits and prolonged overloads. The latter makes them the best choice for powering welding machines. In general, asynchronous generators are designed mainly for active loads: lighting devices, computers, electric heaters, etc. For reactive loads (with coils and capacitors), it is better to use synchronous units (see below). It is also worth noting that in an asynchronous alternator, the voltage and frequency of the output current directly depend on the rotation speed; t...herefore, such devices are particularly demanding on the stability of the drive motor.

— Synchronous. In this type of alternators, the rotation of the rotor and the magnetic field of the stator coincide (unlike asynchronous models). Synchronous generators are somewhat more complex in design and more expensive, they are more sensitive to short circuits and prolonged overloads. On the other hand, such a unit does an excellent job with both resistive and reactive loads: for a short time, it is able to deliver a current many times higher than the rated current, thus providing the necessary starting current for the reactive load. In addition, the design of synchronous generators includes an automatic control unit that outputs a stable voltage and is able to compensate to a certain extent for fluctuations in the speed of the drive motor. However, in terms of voltage stability, synchronous models are still inferior to inverter ones (see below).

— Inverter. Synchronous generator (see above), equipped with an additional electronic unit — an inverter. This block provides double current conversion: from AC to DC and then back to AC. Such devices are not cheap, but they have a number of advantages. Firstly, the output is a very stable current, practically without any jumps and fluctuations. Secondly, the generator is able to regulate the operation of the engine depending on the load: for example, if the load is half of the output power, then the current engine power is halved; this results in significant fuel savings. Thirdly, inverter models are lighter and more compact than traditional generators, and they are less noisy. It is such a generator that is considered the best choice for a load that is sensitive to the quality of the current, such as audio equipment or a TV. At the same time, units of this type have a relatively low power and are not designed for long-term operation or high starting loads, and therefore they are used only as backup power sources for relatively low-power power supply systems. In addition, when choosing an inverter generator, it is worth clarifying the shape of the output signal: not all models give an perfect sine wave — there are also units with a trapezoidal pulse that are not suitable for delicate equipment.

— duplex. Type of alternators developed by Endress and used mainly in generators of this brand (although devices from other manufacturers are also found). According to the creators, such an alternator combines the advantages of synchronous and asynchronous models. So, on the one hand, it is able to withstand high inrush currents without compromising the supply of other consumers, and the design usually has an auto-voltage regulator at the output; on the other hand, most of these generators can also be used to power welding machines, and the number of high-frequency harmonics at the output is very low. The disadvantages of "duplexes", in addition to the high cost, include the need to configure for a specific set of connected devices.

— Copper. Copper winding is typical for advanced class generators. The copper alternator is characterized by high conductivity and low resistance. The conductivity of copper is 1.7 times higher than the conductivity of aluminium, such a winding heats up less, and compounds made of this metal endure temperature drops and vibration loads. Among the disadvantages of the copper winding, one can only note the high cost of the alternator. Otherwise, generators with copper winding have high reliability and durability.

— Aluminium. The aluminium winding of the alternator is typical for low-cost-class generators. The main advantages of aluminium are light weight and low price; otherwise, such a winding is usually inferior to copper counterparts. An oxide film is created on the surface of aluminium, it appears everywhere, even in the places of contact soldering. The oxide film undermines the contacts and does not allow the outer protective braid to securely hold the aluminium conductors.

Model name of the engine installed in the generator. Knowing this name, you can, if necessary, find detailed data on the engine and clarify how it meets your requirements. In addition, model data may be needed for some specific tasks, including maintenance and repair.

Note that modern generators are often equipped with branded engines from famous manufacturers: Honda, John Deere, Mitsubishi, Volvo, etc. Such engines are more expensive than similar units from little-known brands, but this is offset by higher quality and/or solid warranty conditions , and in many cases, the ease of finding spare parts and additional documentation (such as manuals for special maintenance and minor repairs).

The working volume of the engine in a gasoline or diesel generator (see "Fuel"). Theoretically, more volume usually means more power, but in fact, everything is not so clear. Firstly, the specific power strongly depends on the type of fuel, and in gasoline units, also on the type of internal combustion engine (see above). Secondly, similar engines of the same power can have different volumes, and there is a practical point here: with the same power, a larger engine consumes more fuel, but by itself it can cost less.

The operating power of the engine installed in the generator. Traditionally stated in horsepower; 1 HP approximately equal to 735 watts.

First of all, the rated power of the generator directly depends on this indicator (see above): in principle, it cannot be higher than the engine power, moreover, part of the engine power is spent on heat, friction and other losses. And the smaller the difference between these capacities, the higher the efficiency of the generator and the more economical it is. However high efficiency affects the cost, but this difference can pay off with regular use due to fuel savings.

Fuel consumption of a petrol or diesel generator when operating at half power, and for combined models when using petrol (see “Fuel”).

Fuel consumption usually increases with load. However, generator efficiency is not always linear - fuel consumption may vary disproportionately with different loads. In this case, the approximate amount of fuel consumed by the generator when operating at half power (50% of the rated power) is given. Knowing the fuel consumption and tank capacity, you can at least estimate how long one fill-up will last.

The volume of the fuel tank installed in the generator.

Knowing the fuel consumption (see above) and the capacity of the tank, you can calculate the operating time on one gas station (if it is not indicated in the specifications). However, a more capacious tank is also more bulky. Therefore, manufacturers choose tanks based on the general level and "voracity" of the generator — in order to provide an acceptable operating time without a significant increase in size and weight. So in general, this parameter is more of a reference than practically significant.

As for the numbers, in low-power models, tanks are installed for 5 – 10 liters, or even less ; in heavy professional equipment, this figure can exceed 50 liters.