Electromagnets

[Silas Pradetto]

Adrian and I were having a discussion yesterday about electromagnets. This stemmed from some ideas I had using electromagnetic actuators to open some valves, but I won't share my idea until I patent it

.



Anyhow, I was wondering about the strength of electromagnets, and how does the frequency of the voltage source affect the amount of flux generated.



Does anyone know? I know more current/more voltage yields more flux, but how about frequency. Also, how about DC vs AC.



Adrian will be doing some testing at his school but I won't have a chance to play around with anything anytime soon.

 

[Robert Burns]

Re: Electromagnets

This site might help:

http://www.liftonmagnets.com/Resources/Downloads.aspx

It has a download:

Norberto raggio's ELECTROMAGNET DESIGN COOKBOOK

That's fairly straightforward

Addition

http://www.reocities.com/CapeCanaveral/2404/design2.html

 

[Ryan Lantzy]

Re: Electromagnets

Adrian and I were having a discussion yesterday about electromagnets. This stemmed from some ideas I had using electromagnetic actuators to open some valves, but I won't share my idea until I patent it

.



Anyhow, I was wondering about the strength of electromagnets, and how does the frequency of the voltage source affect the amount of flux generated.



Does anyone know? I know more current/more voltage yields more flux, but how about frequency. Also, how about DC vs AC.



Adrian will be doing some testing at his school but I won't have a chance to play around with anything anytime soon.

AFAIK, if you want an electromagnet to work like a regular magnet you have to use direct current. AC would just make the the field switch back and forth in polarity (there may be some use for this in some applications).



If you pantent idea involves the valves on an internal combustion engine, BMW (and others) have been there done that.

 

[Mike Butler (media)]

Re: Electromagnets

AFAIK, if you want an electromagnet to work like a regular magnet you have to use direct current. AC would just make the the field switch back and forth in polarity (there may be some use for this in some applications).

Like motors, relays, solenoids... (oh, and loudspeakers)

 

[Bennett Prescott]

Re: Electromagnets

Fucking magnets! How do they work?

 

[John Roberts]

Re: Electromagnets

You can find solenoid operated valves in dishwashers and washing machines so they are off the shelf parts. Solenoid operated valves for you car or motorcycle are not off the shelf but you can probably find some up in Detroit R&D labs.



JR

 

[Silas Pradetto]

Re: Electromagnets

Adrian and I were having a discussion yesterday about electromagnets. This stemmed from some ideas I had using electromagnetic actuators to open some valves, but I won't share my idea until I patent it

.



Anyhow, I was wondering about the strength of electromagnets, and how does the frequency of the voltage source affect the amount of flux generated.



Does anyone know? I know more current/more voltage yields more flux, but how about frequency. Also, how about DC vs AC.



Adrian will be doing some testing at his school but I won't have a chance to play around with anything anytime soon.

AFAIK, if you want an electromagnet to work like a regular magnet you have to use direct current. AC would just make the the field switch back and forth in polarity (there may be some use for this in some applications).



If you pantent idea involves the valves on an internal combustion engine, BMW (and others) have been there done that.

I know the effect of AC and DC on the electromagnet, but what is the effect of varying the frequency of the AC? I'm sure you won't be able to notice the varying field picking up paperclips with a magnet made from a bolt and some wire.



I'm going to have to try it, using an old amplifier as a voltage/current source.

 

[Robert Burns]

Re: Electromagnets

Is the area of interest hysteresis loss @ frequency?

 

[Silas Pradetto]

Re: Electromagnets

Is the area of interest hysteresis loss @ frequency?

I'm going to have to look that up

The idea was that since higher frequency AC requires a smaller transformer for a certain current, then there must be an effect on the an electromagnet too.

 

[John Roberts]

Re: Electromagnets

Is the area of interest hysteresis loss @ frequency?

I'm going to have to look that up

The idea was that since higher frequency AC requires a smaller transformer for a certain current, then there must be an effect on the an electromagnet too.

I'm afraid you may be making a logical leap, in the wrong direction.



The relationship between size and frequency for magnetics is related to different things and in the application we are most familiar with a different end target.



In something like a switching supply we are trying to transfer power (current) from the primary to the secondary. This transfer only occurs at the very top and bottom of the waveform peaks (due to PS rectification), not during the entire waveform. The higher frequency carrier means we will have more peaks and bottoms to pass more ''small'' pushes of current per unit time, as compared to a conventional heavy iron transformer that only pushes larger pulses of current at 2x 50/60 Hz. The actual magnetic flux that exists inside the small HF transformer is smaller, than the large transformer as you should expect.



If you are trying to get more magnetic flux or a stronger magnetic field you are barking up the wrong tree.. If trying to make a smaller power supply you are OK.



JR

 

[Silas Pradetto]

Re: Electromagnets

Is the area of interest hysteresis loss @ frequency?

I'm going to have to look that up

The idea was that since higher frequency AC requires a smaller transformer for a certain current, then there must be an effect on the an electromagnet too.

I'm afraid you may be making a logical leap, in the wrong direction.



The relationship between size and frequency for magnetics is related to different things and in the application we are most familiar with a different end target.



In something like a switching supply we are trying to transfer power (current) from the primary to the secondary. This transfer only occurs at the very top and bottom of the waveform peaks (due to PS rectification), not during the entire waveform. The higher frequency carrier means we will have more peaks and bottoms to pass more ''small'' pushes of current per unit time, as compared to a conventional heavy iron transformer that only pushes larger pulses of current at 2x 50/60 Hz. The actual magnetic flux that exists inside the small HF transformer is smaller, than the large transformer as you should expect.



If you are trying to get more magnetic flux or a stronger magnetic field you are barking up the wrong tree.. If trying to make a smaller power supply you are OK.



JR

Good information, thanks JR!



I'm not really looking to do anything, just expand my knowledge of the workings of electromagnetics.



Thanks!

 

[Robert Burns]

Re: Electromagnets

Electro magnetic study gets arcane and specialized quickly:

Low/High Speed Linear/Non-Linear etc.

Very Generally speaking losses in AC applications are:

Hysteresis Losses, Coupling Current Losses and Eddy Current Losses.

 

[Ryan Lantzy]

Re: Electromagnets

AFAIK, if you want an electromagnet to work like a regular magnet you have to use direct current. AC would just make the the field switch back and forth in polarity (there may be some use for this in some applications).

Like motors, relays, solenoids... (oh, and loudspeakers)

None of which (excepting loudspeakers) are strictly AC Mike.

 

[Chris Gruber]

Re: Electromagnets

Fucking magnets! How do they work?

ROFL Awesome!