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generator and alternator

Alternators | Alternator Parts

By Mary

Alternator Definition: the electrical generator in a vehicle

The power grid in a vehicle with an internal combustion engine, for example a car or truck, is usually fed by a generator, which is often driven by the engine via a belt. Since the operation of the headlights (i.e. the generation of light for lighting purposes) was originally the most important task of generating electricity on board, the term alternator has become commonplace for the generator. In the meantime, almost every car contains a large number of other electrical consumers, which together require considerably more electrical energy than the headlights.

alternator

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Other names for the alternator are generator and power generator.

Since on the one hand the engine speed and on the other hand the electrical load is variable, a rechargeable battery is generally used as an energy storage device. The same battery serves as a starter battery, i.e. for starting the combustion engine, and for supplying consumers when the combustion engine is switched off. The alternator contains a charge regulator, which enables the battery to be charged properly (with adequate current and avoiding overcharging). It also limits the electrical voltage at high engine speeds to prevent damage to loads.

The regular operating voltage of the vehicle electrical system is quite low in a car: usually about 12 to 14 V, in trucks about twice that. Since the power output in a car can already be several kilowatts, quite high currents are required – sometimes over 200 A. Therefore, the alternator must be connected by quite strong cables, and the contact points must be clean.

If an alternator is defective, this is usually indicated in the car by the charging indicator light continuing to shine even when the engine is running.

Direct current and three-phase alternators

Old alternators, as used until the 1970s, were mostly electrically excited direct current generators. At low engine speeds, at least when idling, the electrical voltage generated was often too low to supply consumers or charge the battery. Nowadays, three-phase generators are almost exclusively used in conjunction with a rectifier, which can deliver considerable power even at low engine speeds. (The transmission ratio for driving a generator is often selected so that the full power can already be delivered at idle speed and two thirds of the full power – which unfortunately means reduced energy efficiency at high engine speeds).

Increasing power demand in vehicles

The alternators of today’s cars are designed for a maximum output of sometimes more than 5 kW, sometimes even for about twice that. In the future, the electrical power requirement is likely to rise even further, since not only are more and more comfort functions being demanded, but also various functions important for the engine itself are increasingly electrified. For example, radiator fans, cooling water pumps, power steering and in some cases even compressors of air conditioning systems are increasingly being operated electrically.

Despite the energy losses in the alternator and electric motors, this can be energetically advantageous, because it enables operation that is better suited to the respective requirements. For example, it is very annoying in car air-conditioning systems that a compressor driven directly by the engine withdraws a certain amount of power from the engine even when the air-conditioning system is not running at all.

Modern starter alternators can replace the alternator and the starter (starter motor); they allow higher power to be produced with greater efficiency than traditional alternators.

As the power output increases, a low on-board voltage of 12 V becomes a limiting factor, because very high electrical currents (e.g. 200 A for a power output of 2.4 kW) occur, and this requires thick and heavy cables. For this reason, significantly higher on-board voltages are likely to be used in the future, and naturally also alternators with a correspondingly higher nominal voltage.

alternator

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Energy efficiency of alternators

The alternator is driven by the combustion engine and brakes it in the process; it therefore absorbs mechanical energy in order to be able to deliver electrical energy. The mechanical power absorbed can be significantly higher than the power output, since considerable energy losses also occur, especially at high engine speeds – for example, due to friction, for driving the fan (fan wheel) that cools the alternator, and due to ohmic losses in the coil windings and in the rectifier. Even without electrical load, the drive of the alternator requires a certain driving power, which then increases accordingly with electrical load (as a result of magnetic forces).

In old cars, the energy efficiency of the alternator was usually quite low; however, only relatively low power was converted anyway. The efficiency could easily be well below 50 %. More efficient devices would have been possible, but were probably not realized due to cost pressure. In modern vehicles, much higher electrical power is needed to supply a large number of consumers; several kilowatts may be required (see above).

Here, the efficiency of the generator becomes more important in order to keep fuel consumption low and also to prevent the cooling effort for the generator from becoming too high: The power lost there becomes heat, which must be safely dissipated to avoid destruction. Unfortunately, the problem with today’s alternators is that high efficiency for a wide range of speeds and loads is difficult to achieve.

Especially the operation at high speed but low load is quite inefficient. Therefore, even a peak efficiency of e.g. 80%, which some modern alternators can achieve, will probably result in an average practical efficiency of only between 50 and 70%. Modern starter generators in combination with suitable power electronics could be even better.

alternator

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Recuperation with alternators

To a very limited extent, alternators can also be used for recuperation, i.e. for the recovery of braking energy in micro-hybrid vehicles. For this, it must be possible to increase the power generated during braking in a targeted manner, and the additional power is fed into the vehicle battery. (At other times, less power can then be generated, so that the engine is less loaded and fuel is saved). The recoverable power can be limited by the alternator or by the battery, usually to a few kilowatts.

In vehicles with a true hybrid drive, both units are much stronger, so that higher braking power can be used; in this case, we no longer speak of an alternator, but of a generator, or possibly a powerful electric machine that can be used as an engine or generator. For the transport of corresponding power, considerably higher electrical voltages are then required (several hundred volts), which is why the normal on-board power supply cannot be used for this purpose.

It is also possible to reduce the power output of an alternator for a short time if there is a high demand for drive power (e.g. when accelerating). In this way, acceleration in particular can be slightly improved without increasing the engine power, and with minimal technical effort.

Starting Current : Guide, Background Information and 5 Valuable Tips

By Mary

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?

starting current

READ NEXT: Best Power Efficiency Guide For Generator

Do start-up currents occur with all consumers?

Basically, three groups of consumers can be distinguished.

Ohmic loads

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.

Inductive consumers

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.

Capacitive consumers

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.

READ NEXT: Generator Transfer Switch

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.

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Alternator and generator: 7 Interesting facts

By Adekunle

difference between generator and alternator

Are you regularly confused between a generator and an alternator?

They surely sound confusing but it is really simple when you come to know the major differences in both these devices.

Both a Generator and an Alternator can be broadly termed as Generators. Meaning both devices are in fact generators with the major differences being in their working, construction and output.

But before you know these differences you must understand certain basics which will be really helpful in understanding the differences.

Alternator and Generator

The working of the generator is based on Michael Faraday’s (1867) laws of electromagnetism. Both a generator and an alternator are used to convert mechanical energy into electrical energy. Hence both of them are used for the same purpose that is to generate electricity. They do this by a process called as “magnetic polarisation”. Both these devices can also be used as electric motors, when it is supplied with electrical energy instead of mechanical energy.

Sale
DuroMax XP13000EH Dual Fuel Portable Generator 13000 Watt Gas or Propane Powered Electric Start-Home Back Up, Blue/Gray
DuroMax XP13000EH Dual Fuel Portable Generator 13000 Watt Gas or Propane Powered Electric Start-Home Back Up, Blue/Gray
  • POWERFUL DUROMAX ENGINE: The XP13000EH is powered by a 500cc OHV Duromax Engine.
  • DUAL FUEL TECHNOLOGY: The ability to run on Propane or Gasoline allows the Freedom and Flexibility of Fuel Choice.
  • PLENTY OF POWER: With 13,000 starting watts and 10,500 watts, this unit can handle heavy loads from lights, refrigerators, home conditioners and high amperage power tools.
  • MAXIMUM POWER: The power panel includes a wide selection of outlets for maximum compatibility in your applications including: 1 120/240V 50A heavy duty outlet, 1 120/240V 30A twist lock outlet, 1 120V 30A twist lock outlet, and 2 120V 20A household outlets.
  • POWERING EVERYONE ANYWHERE: Like all DuroMax generators, the XP13000EH is EPA and CARB approved for use in all 50 states.
$1,399.00
Buy on Amazon

The electricity generated by the generator is supplied to us as two different currents, namely: Alternate Current (AC) and Direct Current (DC)

AC – Alternate Current and DC – Direct Current

In a Direct Current the charged electrons flow directly from one point to another, like a battery where the current flows from the positive point to the negative point.

But in an Alternate Current the flow is reversed for a specific time period. This results in an electron pulse different from that of a Direct Current. The number of times this pulse happens in a second is known as the frequency. The conventional frequency in the U.S is at 60 Hz i.e. the electron pulse happens 60 times in one second.

With these basics in mind, you can now easily differentiate between an alternator and a generator based on the following points.

Working Generator

It is also known as Dynamo or DC Generator.

Generators typically have wire coils that form a rotor. These windings are also called as the armature. This rotor is placed inside a magnetic field made by magnets. Now in a generator these wires are moved mechanically. The magnets do not move. This mechanical movement creates a current in the wires which is the alternate current.

Now the generator has a mechanism known as a commutator which converts that alternate current into direct current and gives the output in DC. The commutator is basically a set of separate rings attaching the generator to an external circuit.

Alternator

Alternator was a term introduced for the better, reliable and more efficient generators released in the late 1950’s. Immediately it became a winner and replaced the generators in the cars for charging the batteries. AC generator is also termed as an alternator.

It is also known as synchronous generator. This is because it works in sync with the power grid it is connected to. They follow the grid’s frequency, EMF and phase. But these are only large alternators.

In alternators the magnetic field moves inside of a winding of wires called as the stator.

Output Generator

The generator is used commonly during a power cut and for generating large-scale electricity.

The output power produced by generator is less than compared to that produced by an alternator.

One of the benefits of a generator is that it can be used as a DC motor also, by applying power to the shaft and vice versa a DC motor can also be used as a DC generator, by turning the shaft on. The power produced in a DC generator is purely from mechanical motion.

As the generator uses all the energy it generates, it can be termed as less efficient than an alternator.

One of the many reasons for the generators being replaced by the alternators is that it drained the batteries of the cars and vehicles when the demand was high, like in wet weather, when you need the windshield wipers and the lights. Using both together would result in low performance. The generator couldn’t provide enough power for both when the engine revs were low.

Now a day’s generator is not in much use as it is not as efficient as an alternator.

Use of Alternator

The most common use of the alternator is in the automobile industry to charge vehicles batteries. The alternators are also more favoured for commercial use beyond cars as it works great with transformers.

An Alternator is more efficient than a generator. One of the reasons for it being efficient is that it generates electricity only when it is needed and it conserves energy by using only the amount of energy required. This prevents over usage and wastage of energy. Even the windings of the wires make the alternator more efficient, because they are the biggest and heaviest parts in both the generator and the alternator. And the alternator keeps it stationary while the generator is moving its heaviest part. This way the alternator can work faster and produce more power at less speed in comparison to a generator.

Alternators are not good for charging dead batteries but generators are good at it.

Both the devices generate electricity as AC. But a generator can give the output in AC as well as DC and the alternator gives the output just as AC

Construction Generator

The design of the generator is simpler when compared to an alternator.

In terms of size a generator usually is large and needs more space than an alternator.

Generators have brushes which collects the power generated from the armature. Like every equipment, the brushes are also subjected to wear off through time, making the generator not so efficient and cost effective.

Alternator

Alternators have a complex and sophisticated design due to the requirements needed to regulate the flow of an Alternate Current.

The alternator does not have brushes which makes it more robust and durable. The Alternate current produced is collected from the stator side and hence there is no need for brushes.

The alternator also does not have a commutator as it does not convert the power to DC.

A safety measure that comes with an alternator is the voltage regulator which ensures that the alternator is not giving extra energy to a battery causing damage to the battery or the surroundings.

Some other differences between the two are:

Polarisation

Alternators do not need to be polarised after they are installed, whereas generators have to be polarised after they have been installed.

Magnetic field

The mechanical energy needed by these devices to generate electricity comes from the rotor and the stator. The alternator receives from the stator while the generator receives from the rotor.

To sum it up the difference between a generator and an alternator is all about what spins and what remains stationary.

Due to its cost effectiveness, less maintenance and increased efficiency an alternator is favoured over the generator these days and now you too know exactly why.

Here are some of the bestselling alternators and generators from the finest companies that produce machineries.

BOSCH AL0807N NEW ALTERNATOR

It promises great quality and premium make for its equipments.

GENERAC 5743 GP15000E 15000 RUNNING WATTS/ 22500 STARTING WATTS ELECTRIC START GAS POWERED PORTABLE GENERATOR.

It is a gas powered generator offering an electric as well as plug start. It Boasts a fuel tank of 16 gallons and provides up to 10 hours of power.

The make is more durable and flexible.

Generac 5734 GP15000E 15000 Running Watts/22500 Starting Watts Electric Start Gas Powered Portable Generator
Generac 5734 GP15000E 15000 Running Watts/22500 Starting Watts Electric Start Gas Powered Portable Generator
  • Generac 992cc OHVI engine incorporates full pressure lubrication with automotive style spin on oil filter for a longer life engine
  • Electric start with battery (included) and plug-in battery charger jack
  • Hour Meter / Low-oil level shutdown / Idle control reduces noise and conserves fuel
  • 16 gallons fuel tank provides up to 10 hours of run time at 50% load
  • Hardened 1 1/4" steel tube cradle for added durability and strength with an integrated lifting eye for easy transport and security on the jobsite
$3,599.00
Buy on Amazon
Sale
DuroMax XP13000EH Dual Fuel Portable Generator 13000 Watt Gas or Propane Powered Electric Start-Home Back Up, Blue/Gray
DuroMax XP13000EH Dual Fuel Portable Generator 13000 Watt Gas or Propane Powered Electric Start-Home Back Up, Blue/Gray
  • POWERFUL DUROMAX ENGINE: The XP13000EH is powered by a 500cc OHV Duromax Engine.
  • DUAL FUEL TECHNOLOGY: The ability to run on Propane or Gasoline allows the Freedom and Flexibility of Fuel Choice.
  • PLENTY OF POWER: With 13,000 starting watts and 10,500 watts, this unit can handle heavy loads from lights, refrigerators, home conditioners and high amperage power tools.
  • MAXIMUM POWER: The power panel includes a wide selection of outlets for maximum compatibility in your applications including: 1 120/240V 50A heavy duty outlet, 1 120/240V 30A twist lock outlet, 1 120V 30A twist lock outlet, and 2 120V 20A household outlets.
  • POWERING EVERYONE ANYWHERE: Like all DuroMax generators, the XP13000EH is EPA and CARB approved for use in all 50 states.
$1,399.00
Buy on Amazon

ACDELCO 335-1086 PROFESSIONAL ALTERNATOR

Sale
ACDelco Gold 335-1086 Alternator
ACDelco Gold 335-1086 Alternator
  • All components are 100% New to provide improved performance
  • Key components are greased to ensure long term reliability in harsh conditions
  • New units are manufactured under the guidelines of ISO Quality Standards to ensure consistent quality
  • ACDelco Professional New Alternators are computer tested for voltage stability, terminal function, and electronic circuit board integrity
  • Engineering enhancements to internal components provide the latest, most efficient unit for your vehicle
$99.99
Buy on Amazon

It comes with lubricated components and computer tested regulators for better voltage stability, terminal function and electronic circuit board integrity.

Related:

Generator transfer switches: must have for safety

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