# Are there any DC generators without brushes and a commutator?

• Quix270
In summary: Text= generator%3A%22dc%22&limitType=text&limitSize=10&limitCount=10In summary, all AC generators need some form of commutation to generate DC. Some use brushes, others use diodes. Some don't have brushes or a commutator at all, and are called " Squirrel-cage AC motors and brushless permanent magnet motors have no brushes. "
Quix270
Are any generator that produce dc current without brushes or commutator?

I don't know of any off the top of my head. Is this a theoretical musing or a more practical inquiry?

hutchphd said:
I don't know of any off the top of my head. Is this a theoretical musing or a more practical inquiry?
Practical Inquiry
So all needs commutator?

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There are no dc generator that produce dc current without commutator or brushes?

You can make AC current without brushes and then rectify it. If you describe why you need to know this we can be more helpful.

So all generator are ac but some have commutators or rectifiers to produce dc?

Quix270 said:
So all generator are ac but some have commutators or rectifiers to produce dc?
There are AC generators without brushes. Please: why do you want to know?

What is this fascination with brushes? It is commutation that is important for DC.

A voltage is generated when a wire moves relative to a magnetic field. The voltage is proportional to the rate-of-change of magnetic flux through the wire loop. Obviously the flux cannot increase forever, so at some point the flux must be reversed, to make AC.

To make DC the connections must be reversed each half cycle, that is called commutation. That reversal can be done with brushes on a commutator, or with asynchronous rectifier diodes as used in a car alternator, or with a synchronous rectifier which senses the position of the rotating magnetic field and electrically switches the appropriate windings to the DC output.

hutchphd and DaveE
You need to state your intended use. Do you want to produce DC current for welding? How many amperes and volts will you need?
Squirrel-cage AC motors and brushless permanent magnet motors have no brushes. Some electronics for safety and control will be needed. A DC generator with brushes and a commutator is a very old technology.
Rather than designing it yourself, it is much safer and less expensive to buy a DC power supply. You can buy a power inverter to generate DC electronically.

Some Homopolar generators manage it. The ionic liquid / liquid metal variety have electrodes, but they do not erode like traditional commutator brushes.

Also, I don't know the internal configuration of a superconducting homopolar generator, but an early type also managed without brushes. I Remembered this from a 'classic' Scientific American article on research-grade superconducting electromagnets, where the 'test coil' was 'close coupled' to the generator stator...

FWIW, a multi-pole stepper motor plus diode rectifier array for the resulting polyphase AC will give you fair DC without brushes or mechanical commutation. As not engineered for this task, efficiency is likely to be sub-optimal...

Um, what are you trying to achieve ??

Quix270 said:
Are any generator that produce dc current without brushes or commutator?
The very first generator, or dynamo, was made by Michael Faraday and gave a DC output. It did not have a reversing device (commutator) but it did have one rubbing contact. It can be seen in his laboratory at the Royal Institution, London.

## 1. What is a DC generator without brushes and a commutator?

A DC generator without brushes and a commutator is a type of electrical generator that converts mechanical energy into direct current (DC) without the use of brushes and a commutator. It uses a different type of technology, such as permanent magnets or electronic switches, to produce DC power.

## 2. How does a DC generator without brushes and a commutator work?

A DC generator without brushes and a commutator works by using a stationary set of permanent magnets and a rotating set of electromagnets to create a magnetic field. As the electromagnets rotate, the magnetic field changes, inducing an electric current in the stationary coils. This current is then collected and converted into DC power.

## 3. What are the advantages of using a DC generator without brushes and a commutator?

There are several advantages to using a DC generator without brushes and a commutator. These include improved efficiency, reduced maintenance, and longer lifespan due to the absence of mechanical parts that can wear out. Additionally, these generators can be made smaller and lighter than traditional generators, making them ideal for portable applications.

## 4. Are there any limitations to using a DC generator without brushes and a commutator?

While there are many benefits to using a DC generator without brushes and a commutator, there are also some limitations. These generators are typically more expensive to manufacture and may require more sophisticated control systems. They may also have lower power output compared to traditional generators, making them better suited for smaller-scale applications.

## 5. What are some common applications of DC generators without brushes and a commutator?

DC generators without brushes and a commutator are commonly used in portable electronics, such as laptops, cell phones, and handheld power tools. They are also used in renewable energy systems, such as wind turbines and solar panels, as well as in electric vehicles. Additionally, they can be found in industrial applications, such as conveyor systems and manufacturing equipment.

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