AC and DC Alternator. working principle, maintenance and troubleshooting.

You can utilize different types of alternators in different engines. They depend on the alternator's intended application, the machine's specifications, and the battery. Everything you need to know about alternators, the distinctions between AC and DC, and potential advantages are on this page.

AC Alternator 

You use AC alternators for standby power generation, which provides clean power for the things you care about most. 

 It uses a high rotation speed to induce a magnetic field to produce a varying current. Tracking down the cause of your alternator problems can be difficult. Because it is not a standard system and contains numerous unique components, issues can arise in multiple ways. Here, we'll look at the details of an alternator and what they do.

Significant components of AC Alternator 

An AC (alternating current) alternator is a device that converts mechanical energy into electrical energy. It consists of several key components, including:

  1. Stator: The stator is the alternator's stationary component. It comprises several copper wire–wound electromagnets made from laminated iron cores.

  1. Rotor: The alternator's revolving component is known as the rotor. A shaft, magnets, and several windings make up the rotor.

  1. Exciter: The exciter is a tiny DC (direct current) generator that starts the alternator's magnetic field.

  1. Regulator: The regulator controls the output voltage of the alternator. It consists of a series of diodes and other electronic components that control the flow of electricity from the alternator to the load.

  1. Bearings: The alternator uses approaches to support the rotor and allow it to rotate smoothly.

  1. Cooling system: The alternator generates a lot of heat during operation, so it typically includes a cooling system to keep the components from overheating. It may be a fan or some other cooling mechanism.

  1. Housing: The housing encloses and protects the other components of the alternator.

The three main components of an AC alternator in a diesel engine electric generator are the stator, rotor, and exciter. Each of these components has a specific function that is essential to the operation of the generator.

AC Alternator maintenance.

AC Alternator is an essential component in a diesel engine electric generator that you can't afford to take lightly. You should check all diesel engine alternators routinely. You should know when to maintain your diesel generator and how you should do it. 

The maintenance of the alternator is essential for your diesel generator operation. It is part of the diesel generator that generates electricity. So, you need to know how to maintain it. You need to know how and how often you should check it. You also need to understand how to keep it. It is imperative to see this information.

When your diesel engine electric generator AC alternator is not maintained properly, you may face many problems. You must regularly maintain your diesel engine electric generator AC alternator to keep it in good working condition.

You can seek assistance from a reputable diesel generator AC alternator servicing firm to maintain your diesel engine electric generator AC alternator.

Preventative care.

It would be best to avoid breakdowns and efficiency loss before they happen; you perform preventive maintenance on a system, equipment, or other apparatus. It is meant you put off costly maintenance, replacement, or the loss of functionality for the machine, design, or another device. Preventive care is typically carried out on a schedule to reduce the danger of equipment or system malfunctioning and to necessitate an expensive repair or replacement.

The type of equipment maintained and the usage circumstances can significantly impact how frequently inspections and maintenance you perform. A generator engine, for instance, would need standard care every 200 to 250 hours while needing an overhaul every 10,000 hours.

The Manual for Alternator advises that you test the insulating property of the coil at the first usage. 

Give special attention to the storage location's humidity if the generator is no longer for standby use. Generally speaking, test the insulation degree every 3-6 months. When the machine is not in use in a high-humidity area, you install a heater to drive the humidity out, which will help the coil stay dry.

If you install an air filter with the alternator, then the routine inspection must be done by the local climate.

If cleaning is required, remove the filter's components and submerge or wash them; add stain remover as needed until the cloth is clean. Before reinstallation, let the materials air dry completely.

Regular cleanings of the alternator's interior and exterior are required. However, the machine's surroundings will determine how frequently it needs to clean. When cleaning the alternator is required, please follow the instructions below.

To prevent these objects from entering the coil and causing damage to the insulation, turn off all power sources, clean the ventilation net, and wipe off any liquids, dust, dirt, oil deposits, water, and other contaminants.

Using a dust collector to absorb the dust and grime is preferable to cleaning it with an air blow or high-pressure water spray.

How to troubleshoot an AC Alternator?

1. The voltage between the neutral line of the alternator and the ground is irregular.

(I) . Under normal circumstances, the magnetic potential and air gap under each magnetic pole are unequal due to high-order harmonics' impact or the manufacturing process. There will be no danger and no need to deal with the voltage if it is between one and several volts.

(ii) . The alternator winding has poor insulation to the ground or a short circuit, which affects the alternator's performance and makes it more likely to overheat.

Therefore, quick maintenance is required to stop the situation from getting worse.

(iii) When there is no load, there is no voltage between the neutral line and the ground; however, when there is a load, voltage is present due to a three-phase imbalance. If your want to balance the three-phase load, it needs to be changed.

2. An overheated alternator.

(I). The alternator does not function under the required technical circumstances. Too low a frequency, too much stator winding copper loss, too much load current, and too high stator voltage all slow down the cooling fan's rotational speed, which impacts the alternator's ability to dissipate heat. Additionally, too little power causes the rotor excitation current to grow, heating the rotor.

(ii). The alternator's three-phase load current is out of balance, which causes the overload one-phase winding to overheat. If the three-phase current difference is greater than 10% of the rated current, there is a severe imbalance in the phase current. The pole winding and ferrule will heat up due to the unbalanced three-phase current producing a negative sequence magnetic field, increasing loss. The three-phase load needs to be changed to keep the current balance as stable as possible.

(iii) Because of the poor ventilation and the dust-clogged air duct, heat radiation is problematic. To make the air duct clear, we should remove dust and grease dirt.

(iv). The cooler is blocked, and the air or water intake temperature is too high. We must lower the temperatures at the water and air intakes and clear the clog in the cooler. Limiting the load on the alternator will help to reduce the temperature before troubleshooting.

(v).  A bearing with too much or too little grease According to rules, oil should be supplied, typically filling half to three-quarters of the bearing chamber (the upper limit for the lower speed and the lower limit for the higher rate), with a maximum fill level of seventy percent.

(vi). Bearing wear If there is no severe wear, the bearing will get locally overheated. Serious wear could result in friction between the stator and rotor, which would heat the stator and rotor. We should examine the bearing to see if there is any noise. If you find friction between the stator and rotor, replace the approach or immediately halt the unit for repair.

(vii). The stator core's insulation damage will result in a short circuit between the pieces, which will increase the iron core's eddy current loss and produce heat. In extreme circumstances, the stator winding will sustain damage. As soon as possible, halt the machine for maintenance.

(viii). The stator windings parallel conductor is broken, which causes the current in other wires to flow more freely and produce heat. As soon as possible, halt the machine for maintenance.

3. Alternator: too much current.

(I). Overload. It would help if you reduced the load.

(ii). You should overhaul the transmission line in case of a phase-to-phase short circuit or grounding problem, and it can resume regular operation after troubleshooting.

4. Too much voltage at the generator's terminals.

(i). You should lower the voltage of the parallel generators if the grid voltage of the generators connected to the power grid is too high.

(ii). You should repair the excitation device promptly if a fault results in overexcitation.

5. Insufficient power.

The generator terminal voltage is lower than the grid voltage as a result of the excitation device's voltage source's inadequate compound excitation compensation, which prevents it from supplying the excitation current needed to excite the armature reaction and prevents the delivery of the rated reactive power. It would help if you took the following actions:

(i). A three-phase voltage regulator is connected between the generator and the excitation reactor to increase the generator's terminal voltage and gradually increase the magnetic potential of the excitation device.

6.  Inadequate power.

The excitation current required by the armature reaction cannot be provided due to insufficient compound excitation compensation of the voltage source of the excitation device, resulting in the generator terminal voltage being lower than the grid voltage and the inability to deliver the rated reactive power. It would help if you took the following actions:

(I). A three-phase voltage regulator is connected between the generator and the excitation reactor to increase the generator's terminal voltage and progressively boost the magnetic potential of the excitation device.

(ii). By adjusting the phase between the voltage and magnetic flux potential of the excitation device and the voltage at the generator terminal, it is possible to increase the total magnetic flux potential and parallelize a resistance of several thousand and 10W at both ends of each phase winding of the reactor.

(iii). Lowering the resistance of the rheostat increases the generator's excitation current.

7. Alternator loses its remaining magnetism and cannot produce power when turned on.

(i). The residual magnetism is frequently lost after shutdown because the material used for the exciter's magnetic pole is close to soft steel and has a lower residual magnetism. The magnetic field will vanish after shutdown when no current flows through the excitation coil. Batteries should be provided and magnetized before power generation.

(ii). When the generator's magnetic pole loses its magnetism, a DC (for a brief period) more significant than the rated current should be fed into the winding to magnetize it, restoring enough remanence in the process.

8. The temperature of the excitation reactor of the automatic excitation device is too high.

(i). You should repair the Reactors if the reactor coil is locally short-circuited. 

(ii). The magnetic course's air gap needs to be modified because the air gap of the reactor's magnetic circuit is too large.

9. After you start the generator, the voltage cannot rise.

(i). The voltage cannot increase because the excitation circuit is faulty. Verify the contact's quality and the excitation circuit's integrity.

Batteries should be provided and magnetized before power generation.

(ii). To restore sufficient remanence when the generator's magnetic pole loses its magnetism, a DC into the winding that is (temporarily) greater than the rated current should be applied.

10. The automatic excitation device excitation reactor's temperature is too high.

(i). The reactor needs to be repaired if you suspect the reactor coil is locally short out.

(ii). The magnetic circuit's air gap needs to be adjusted because the reactor's air gap is too large.

11. The voltage cannot increase once the generator is running.

(i). The voltage cannot increase because the excitation circuit is disconnected. Verify the contact's quality and the excitation circuit's integrity.

(ii). The exciter should be magnetized if there is no instruction on the exciter voltmeter that the residual magnetism disappears.

(iii). The exciter's magnetic field coil's polarity is switched, and the positive and negative connecting lines need to be changed.

(iv). The magnetic field coil is incorrectly connected to reverse direct current while performing some tests during generator maintenance, which results in the disappearance or reversal of the residual magnetism. Therefore, it is necessary to repeat the magnetization.

DC Alternator.

DC alternator is a dynamo mainly used in automobiles, diesel engines, machine tools, etc. It is also called the direct current generator or the direct current dynamo. 

The working principle of a DC alternator is that it can produce a direct current according to the relative movement between the armature and the magnetic field.

Components for a DC alternator.

A DC alternator is an electrical generator that converts mechanical energy into direct current (DC) electrical energy. The main components of a DC alternator are:

  1. Rotor: The rotor is a magnet that rotates inside the stator. Iron or steel, both magnetic, are the typical materials used to make it.

  1. Stator: The stator is a stationary part of the alternator that surrounds the rotor. It consists of a series of copper wire windings that generate an alternating current (AC) voltage.

  1. Rectifier: The rectifier is a device that converts the AC voltage produced by the stator into a DC voltage. Diodes, which only permit current to flow in one way, are frequently used in a chain to accomplish this.

  1. Regulator: The regulator is a device that controls the output of the alternator by regulating the amount of current flowing through the rotor. Usually, you use a feedback loop to compare the alternator's work to a reference voltage.

  1. Bearings: The bearings support the rotor and allow it to rotate smoothly inside the stator.

  1. Housing: The housing is a protective enclosure that surrounds the alternator and keeps it from being damaged.

  1. Fan: You use the fan to cool the alternator by circulating air over its surface.

  1. Pulley: The pulley drives the alternator using a belt or chain.

  1. Terminal: The terminal is a point of connection that provides access to the alternator's output.

DC Alternator Maintenance 

Here are some tips for maintaining your DC alternator:

  1. Follow the manufacturer's recommendations: Consult the owner's manual or website for specific maintenance recommendations for your alternator.

  1. Please keep it clean: Keep the alternator clean and free of dirt and debris. It will help to improve its efficiency and extend its lifespan.

  1. Check the belts: Ensure the belts that drive the alternator are in good condition and properly tensioned.

  1. Check the brushes: The brushes in the alternator are responsible for transferring electricity from the stator to the rotor. Please make sure they are in good condition and properly seated.

  1. Check the bearings: The alternator's bearings help support the rotor and allow it to rotate smoothly. Make sure they are lubricated and in good condition.

  1. Check the output: Regularly test the work of the alternator to ensure it is functioning properly 

  1. Check the wiring: Ensure all the wiring connected to the alternator is in good condition and properly secured.

  1. Replace worn or damaged parts: If any parts of the alternator are worn or damaged, you should replace them as soon as possible.

By following these tips and having regular maintenance performed, you can help to ensure that your DC alternator is operating at its best and prolonging its lifespan.

A direct current (DC) alternator is an electrical machine that converts mechanical energy to electrical energy. The induced voltage is generated in the rotor circuit as the armature rotates within the stator's magnetic field.

This voltage is a function of the rotational speed, number of poles, and magnetic field strength. The DC system is usually a 24-volt system, but you can vary from as low as 6 volts to as high as 72 volts.

Depending on the type of alternator, it’s easy to maintain, and it may be able to last up to 5 years. You can follow the steps outlined in the maintenance manual for quick, easy, and affordable maintenance.

How to check a DC alternator?

You don't need to know much about the diesel generator DC alternator to check if it's not working. The following method is simple and effective.

A diesel engine alternator is a rotating electric machine that converts the kinetic energy of the diesel engine into electrical energy. As a vital component of the diesel engine's electrical power system, the alternator is indispensable. 

If the alternator of the diesel engine is not working, it will affect the regular operation of the diesel engine's electric generator. Then it can not supply stable and robust electric power for driving and lighting, which makes the diesel generator set out of control.

Check an alternator and make it function correctly. 

1: Inspect the battery and cables, paying close attention to the wires and connections. If there is any damage, replace both the battery and the lines. (If you'd like, complete this step first.)

2. Verify the voltage of the batteries:

To prevent sparks, first, unplug the positive and negative connections from the battery. The voltmeter should then be used and set to the voltage scale.

Connect the positive cable to the battery's positive and negative terminals, respectively. If the voltage rises below 12 volts, the battery is discharged and needs to charge.

The alternator correctly charges the battery if the voltage exceeds 12 volts.

3. Verify the armature to see if it is rotating. If so, the alternator is operating correctly. Check the battery next. If the storm "is sealed," the liquid should be inside, and you should charge it. 

The readings from the control module will help you know if the alternator is charging. 


In conclusion, we need to know the importance of AC and DC Alternator because without knowing what AC and DC Alternator are, we won’t understand why we need them.


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