The term “starting current” is used regularly in connection with power generators. In addition, we know from our daily business that especially newcomers to the world of mobile power generation often find this topic difficult to deal with or there is a general lack of knowledge. The non-compliance with a few important rules can however quickly become a major problem for any power generator, since in the worst case capital damage is imminent.
Why is the starting current important?
Certain consumers (which ones, we will discuss in more detail in the next paragraph) require a multiple of the actual rated power when starting. These power peaks are only called up for a short time, BUT they have to be controlled by the power generator.
Conventional generators, e.g. simple converters, can still handle these peaks relatively well. These devices do not have such sophisticated electronics as the more advanced inverter power generators. The simpler design of the converters is more resistant to overload, but these devices cannot deliver a clean and harmonic sine wave voltage in mains quality as the inverter generators can. In general, the following can, therefore, be stated: Too high starting currents can bring generators to their knees. Even severe damage cannot be excluded.
Therefore it is essential to deal with the starting-up currents of the consumers in depth. With the information on this page, the search for a sufficiently powerful generator will be much easier. But what types of consumers are there and do all of them have the dreaded starting currents?
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Do start-up currents occur with all consumers?
Basically, three groups of consumers can be distinguished.
Radiators, construction radiators or hotplates can be added to this class. They are defined by the fact that the power consumed (watts) is converted into brightness or heat. Therefore they are also called active power consumers. For the electric generator, this class is the least problematic, since with Ohm’s consumers the output power corresponds exactly to the input power from the electricity generator. Or to put it in a nutshell: Ohmic consumers have no starting current.
The next big class are the so-called inductive power consumers. These include electric hand tools (chain saw, drill, compressor, circular saw, etc.). Here the matter becomes a little more complicated. These devices have their own built-in motor and this has to “get going” first – and this is where the infamous start-up current comes in.
Let us imagine a bicycle that has to be accelerated quickly from a standing position. This requires a little extra power in the calves. But once the bike has started to move, it is noticeably more comfortable. The starting behaviour of an inductive consumer is similar.
Before buying a generator, you should therefore be aware of the following points:
What is the rated output of the consumers I plan to connect?
Do these consumers need a starting current when starting?
This information can be found in the respective manual. It may be necessary to contact the manufacturer, who will be able to provide the exact characteristics. Tip: Considering the performance of the generator, allow for some “air up”. 20 to 30 % is optimal. On the one hand, this protects the engine (= extension of the product life), on the other hand, the operating volume of the generator is significantly reduced.
This is probably the most critical group of consumers, but fortunately very few will come into contact with these consumers. Examples are discharge lamps or flashlights that have a charging function. In order to satisfy their hunger for electricity, special extra equipment is needed: a Barber-Colman regulator. “Normal” power generators, which are mainly available on the market, will not be able to provide the required starting current of a capacitive consumer.
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Can the starting current be calculated and how long does it last?
That would be nice, of course, but unfortunately, it does not quite work that way. The individual consumers and their motors are too different. As a rough value, however, the 2 to 6 times the value of the actual rated power has become common.
In the following, we would like to give a few concrete examples from our everyday business to give a better picture of the dimensions:
Metabo crosscut and miter saw KGS 216 M, rated power 1500 W, 3 times the starting current, thus 4500 W for a short time
Gardena 4000/4 electronic domestic water dispenser, rated output 800 W, approx. 3.5 times the starting current, therefore 2800 W for a short time
Makita chain saw UC4020A, rated power 1800W, 3 – 3.5 times starting current, thus briefly up to 6300 W
But how long must an electricity generator be able to handle these power peaks? The duration of the starting current differs greatly from consumer to consumer, so that unfortunately no exact specification is possible at this point. Usually, it is “only” a fraction of a second, we are talking about milliseconds. Even in extreme cases, the motor reaches its target speed after a few seconds.
What is the best way to deal with the dangers of starting current?
The best advice here is: Inform sufficiently in advance is everything! This is the only way to make the right choice of an adequately dimensioned generator. The most important key data are the rated power of the loads to be connected and whether a starting current occurs (inductive loads). If this is the case, studying the product instructions or asking the manufacturer will help. With this information you are on the safe side and a correspondingly powerful generator should be found quickly.
Modern devices, such as inverter generators, usually come with an overload protection. In case of too large power demands (e.g. starting current) this trips and switches off the power generator before major damage to the sensitive electronics occurs. However, the overload protection should never be intentionally overloaded in the long run to avoid damage to the device.
Also the possibility of starting current limiters (also called soft starters) should be mentioned here. These devices limit the current peaks and thus protect the electronics of the power generator from fatal overloads. Specialist dealers and a relevant online sales platform will help you find what you are looking for.