DC Power Generation

Add a full wave rectifier. Diodes

My aim in asking the subject question was to know whether there is any possibility to generate DC power in the stator winding of an Elec M/c, even with out the use of conventional commutators or rectifier systems.

However, thank 'U' for taking interest in repplying to my question.

Regards.

The answer might have to be, no, I don't think so. DC generators turn a coil of wire in a magnetic field. An AC generator turns a magnetic field into a coil. You kind of get one or the other. DC generators do produce half a sin wave, but on the positive/negative side. This happens because of the rise and fall of the of the voltage as the lines of the magnetic field are cutting across the rotor coils of wire.

DC into a AC generator is required to create a magnetic field in the rotor. The lines of the magnetic field slice into the coils situated around the stator. The reason you are asking the question, maybe, is because of the slip rings at the end of the rotor. They are there to supply power to the rotor. This is called the excitation field. Tapping into it would cause your AC generator to operate in an unknown fashion as this field regulates the output.

Cheers

You can generate A.C power which by using bridge rectifier and filter circuit can be converted to D.C power.

My aim in asking the subject question was to know whether there is any possibility to generate DC power in the stator winding of an Elec M/c, even with out the use of conventional commutators or rectifier systems.

Thank 'U' very much for taking interest in repplying to my question.

Regards.

Without commutation or rectifiers DC voltage generation is clearly impossible to make with a circular motion generator. Now a linear generator with an infinitely long stator could produce DC voltage without rectification. This scenario is one of the classic classroom problems for electrical engineering. But for obvious reasons this cannot be fabricated.

As Curly would say "Why soitenly" (hmm the spell checker is going to freak on that one.) Earlier cars had DC generators instead of alternators. When silicon diodes made rectification more compact the higher efficiency of alternators replaced the DC generators used at the time. If you wish to try for yourself, find a DC brush motor that you can wire separately the stator and rotor fields. Wire only the rotor to a voltage source to create the magnetic field. Turn the motor shaft with a prime mover and viola, DC power on the stator. You will see a slight tick as rotor poles have to reverse polarity as the brush contact opens the circuit.

With this method can dc power be generated in bulk quanties ? If so why can't this method ( which aviods usage of commutator which is a trouble giving part of the conventional dc generator ) be used to generate dc power and use where ever dc is required in large quanties such as railway traction( avoiding big junk of rectification mechanism which is costly and troubleshooting one), bulk chemical, electroplating,galvenising process units, high voltage dc transmission etc.

I think that DC is a better option than AC, provided that it could be produced directly in a machine without commutator and without rectifiers , and at the required high voltage for each application.

The advantage of the AC, is that its tension or voltage can be converted easily up and down with static transformers and that in three or one phase systems is able to create rotatory fields very easily.

On the contrary, AC is disadvantageous for transmission and utilities distribution networks, because of the skin effect loses and phase imbalance, electromagnetic interferences and other reasons. In fact AC is converted to DC in many applications.

AC replaced DC because DC can not be produced in bulk quantities without commutators and rectifiers, and because AC can be transformed to DC very easily.

Nevertheless I think that it is worth to investigate how to produce DC without rectifiers or without commutator or collecting rings.

Indeed, the fuel cells, produce DC

I am working in this direction, but no with fuel cells.

Best regards,

Arturo.

The problem as I see is that the variable magnetic field can only induce an emf in the secondary coil

This variable field is optimum if it is sinusoidal (Remember fourier) since you cal optimise all your reactances to this value of frequency.

This sinusoid has to be now rectified to become DC.

In DC/ Motor/ Generator, this activity is carried out by the commutators with the known disadvantages.

In modern systems, we have the both advantages-

Generate power in AC without the hassles, (Optimum with AC)

Step Up to transmission voltage (optimum with AC)

use SCR controlled rectifier and convert to DC (non rotating rectification)

Transmit in DC (optimum usage of condutors and insulators)

Convert to AC (SCR controlled inverters)

Step down and transmit

If you want to generate the DC as it is - you always have solars, fuel cells, chemical cells and other mechanism.

But as on date, as far as I know, generation by rotating machine is optimum in AC.