8/16/2023 0 Comments Spike collar generator![]() Some alternators are wired in a similar fashion, with the protective earth centre-tapped to the winding – in much the same way as the Reduced Low Voltage (RLV) system is designed, but with twice the operating voltage. Most multifunction test instruments will see this as a fault and refuse to function if you join earth and ‘neutral’ together to create a traditional set-up, then the output devices will fail catastrophically. This gives 115 V between line and earth and 230 V between lines. The topology in Figure 1 can confuse many, as the earth is ‘centre-tapped’ about the supply rails. This explains the growing popularity of the inverter topology (Figure 1) this design will operate with a wide range of leading or lagging PF loads. However, the PFs of the supplies tend to be slightly capacitive (leading) rather than inductive (lagging) and this causes instability in alternators, usually resulting in the generator shutting down or hunting.Ī generator can work with quite inductive loads (they just burn more fuel, hence power factor correction (PFC) is popular), but if the PF swings the other way and becomes even mildly capacitive, generators struggle considerably, as the leading current causes (in broad terms) the alternator to accelerate. This is because the ubiquitous switched-mode power supply (SMPS), found in everything from PCs to LED lights, typically have power factors (PFs) near to unity. Much has changed over the years alternators and their wiring configurations now come in a variety of configurations, including switchable single- or three-phase, star or delta, 110 V and 230 V dual outputs, self-exciting regulation and automatic regulation – and we are also now seeing inverter-based generators, designed to handle modern loads without issue. It is unclear what the original engineering rationale was for the different power levels it is probably a legacy of early generating set topologies when alternator configurations were quite simple and uniform. Putting it into perspective, it is just as possible to get an injurious electric shock from a 2 kVA generator as it is from a 12 kVA one. Most guidance published to date has been based on these two options. ![]() However, the sections covering generators were for a long time based on two rather historic principles – namely, that generators under 10 kVA typically didn’t need earthing, and that those over 10 kVA did. This document has been updated many times in recent years and provides useful advice on designing earth electrode networks, the earthing of low and high voltage installations, and more. Most guidance in the area of generator earthing stems from BS 7430 Code of Practice for protective earthing of electrical installations. But Earth can be, and is, used for fault protection with low-voltage generator based installations. This again is a myth – in typical low voltage generators the mass of Earth plays no part in the electrical performance of the alternator (or inverter), and a generating set will still output 230 V, whether the frame or winding(s) is connected to Earth or not. It is often said that a generator must be ‘referenced’ to Earth. It is not unusual to see in generator operator manuals a requirement that the generator frame must be connected to an earth electrode, when in practice (given the way the alternator is configured), doing so will provide absolutely no benefit or electrical protection whatsoever. The issue is not just with the way in which generator sets are used however, it is not uncommon for manufacturers’ instructions to be confused on the subject too. The earthing of generator sets has long been a source of confusion, particularly with smaller units like those used to power mobile units, such as catering vans or offices on construction sites. ![]() ![]() True or false? All generators need to be earthed unless floatingīeing a mythbuster column, this statement is, of course, untrue – not least because the term ‘floating’ is technically undefined, so is a meaningless expression. ![]()
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