#ac generator

Magnetic Effects Of Electric Current 1 Do magnets attract all metallic objects? MYTH: Magnets attract metallic objects FACT: Magnets attract ferrous metals only. Magnets attract objects made of magnetic materials like, Iron, Nickel, Cobalt etc. which are also ferrous metals. Several metals like Copper, Silver , gold etc. are not attracted by magnets at all. 2 If there is a magnetic field around a…

AC generator

Most commercial machines and equipment is AC generator. However, commercial DC generator are commonly founded in electromagnetic applications. Some are used in Traction applications like subways and trains. Some DC motor-generator sets provide the field currents for large commercial power Alternators/ AC generators as in hydro-electric dams.

Generator working principle: Generator works by moving electrical conductors through a magnetic field. If your generator doesn’t have magnets, it won’t produce electricity. The magnetic field is created by taking some of the generator output voltage and converting it to DC and feeding it to a coil to make an electro magnet. In other words, the process of converting energy is performed by electromagnetic induction. There are also two types of generators and these produce currents that differ in terms of the manner in which they move.  

All electrical generators whether AC or DC, depend upon principle of magnetic induction regardless of their size. In a DC generator, the armature is always the rotor. In alternators, the armature may be either the rotor or stator.

Although both generators produce current using the same process, they have different design, mechanisms, uses, output connection and types.

First - design differences

As mentioned before, both AC and DC generators produce currents via electromagnetic induction. In AC generators, the coil through which the current flows is fixed, and the magnet is moving. The magnet’s north and south poles cause the current to flow in opposite directions, producing an alternating current. With DC generators, the coil through which the current flows rotates in a fixed field. The two ends of the coil attach to a commutator: different halves of a single, rotating split ring. Metal brushes connect these split rings to an external circuit. The commutator balances the charges leaving and returning to the generator, resulting in a current that does not change direction.

Second - Mechanism

Please know that both AC and DC generators follow electromagnetic principles, yet these two machines have difference means of collecting and transferring induced electromotive forces in the external circuit. Since the connection of external circuit and armature varies with these two types of generators, this explains the difference in how electromotive forces are collected and transferred.

AC generators have two commutators while DC generators have only one. The slip ring contains two semi-circular metal rings. These rings are insulated from one another.  AC generators produce an output voltage called alternators. On the other hand, DC generators produce a steady output voltage.

Third - Primary Uses of AC and DC Generators

AC and DC generators serve different uses. AC generators are used to power small motors and common electrical appliances at home. These appliances that can be operated using AC generators  include vacuum cleaners, food mixers, juicers and electrical fixtures. However, DC generators are functional in supplying power to large electric motors — such as those needed for subway systems. Moreover, DC generators provide a reliable and efficient energy supply that can charge banks of batteries used for mobile and off-grid uses.

Fourth - Output connections

In the alternator used in AC generator, the generated AC is brought to the load unchanged by means of slip rings.

In the DC generator, the emf generated in the armature windings is converted from AC to DC by means of the commutator.

Fifth - Types

An AVR is at the heart of devices often called power conditioners or power stabilizers. The typical power conditioner is an automatic voltage regulator combined with one or more other power-quality capabilities, such as:

1) Surge suppression

2) Short circuit protection (circuit breaker)

3) Line noise reduction

4) Phase-to-phase voltage balancing

5) Harmonic filtering, etc.

Power conditioners are typically used in low voltage (<600V) applications and sizes below 2,000KVA.

In general, the AC automatic voltage regulator (AVR) is a device designed to regulate voltage automatically – that is, to take a fluctuating voltage level and turn it into a constant voltage level.

Working principle of AVR

The voltage regulator is an adjustment device that controls the generator output voltage within a specified range. Its function is to automatically control the generator voltage and keep it constant when the rotating speed of the generator changes, so as to prevent the generator voltage from being too high to burn out the electrical equipment and cause the battery to overcharge. At the same time, it also prevents the generator voltage from being too low, resulting in malfunctioning of electrical equipment and insufficient battery charge.

Since the transmission ratio of generator to engine is fixed, the speed of generator will change with the change of engine speed. The power supply of generator to electric equipment and charging to battery both require its voltage to be stable, so it is necessary to adjust the output voltage of generator if the voltage is kept at a certain value basically.

A synchronous generator regulator that maintains the synchronous generator voltage at a predetermined value or changes the terminal voltage as planned.

When the terminal voltage and reactive power of the synchronous motor change, the output current of the exciter is automatically controlled according to the corresponding feedback signal to achieve the purpose of automatically regulating the terminal voltage or reactive power of the synchronous motor.

According to the working principle, the voltage regulator of alternator is divided  into:

1. Contact type voltage regulator

Contact type voltage regulator was applied earlier, the regulator contact vibration frequency is slow, there is mechanical inertia and electromagnetic inertia, voltage regulation accuracy is low, contact is easy to generate sparks, large radio interference, poor reliability, short life, now has been eliminated.

2. Transistor regulator

With the development of semiconductor technology, transistor regulator is adopted. The advantages is high switching frequency of triode, no sparks, high adjusting precision, light weight, small volume, long life, high reliability, small radio interference and so on. Now it is widely used in medium and low grade car model.

3. Ic regulator (Integrated circuit regulator)

In addition to the advantages of the transistor regulator, the integrated circuit regulator has an ultra-small size and is installed inside the generator (also known as a built-in regulator), which reduces the external wiring and improves the cooling effect. It is now widely used in Santana, Audi and other car models.

4. Computer controlled regulator

After the total load of the system is measured by the electric load detector, a signal is sent to the generator computer, and then the generator voltage regulator is controlled by the engine computer, and the magnetic field circuit is turned on and off in a timely manner, thereby reliably ensuring the normal operation of the electrical system, the battery is fully charged,  and can reduce engine load and improve fuel economy. Such regulators are used on car generators such as Shanghai Buick and Guangzhou Honda.

Introduction of Shanghai KEPU AC Generator

KEPU Series Production

KEPU alternator is mainly divided into STC Series, TFW Series generators and GTF Series high voltage generators. Frame size is from 225mm ~ 630mm. Structural style includes single bearing and double bearing points. The generator protection level is IP21, IP22, IP23, IP24, etc. Rated power is from 8KW to 3200KW, rated voltage is from 110V to 13800V, rated freuency is from…

1. Maintenance of Starlight Generators a. Generator should be installed in the dry, clean, ventilating place, and to prevent the direct contact of wind driven dirt, rain, snow and sunlight. b. Take note of the ventilation and heating of generator at times, and the current and voltage don’t exceed the rating data. c. The generator should not be operated at the place that full of water vapor,dust…

How to Inspect and Operate Starlight TFW Series Generator

Usually, AC generator is used in a diesel generator set. In this article, we will introduce Starlight TFW Series alternator related information. Inspection and operation Inspection Though the generator, AVR and auxiliary devices are solid and well insulated, if the generator was stored for longtime it might be moistened, and should be inspected carefully before operation. Measure the insulating…