Efficiency of solenoid 2

[engineered8]

What is the typical efficiency of a solenoid, neglecting friction? This would be a for a solenoid cycling very fast (with a spring or something to return it to the starting position). Or more importantly, what prevents a solenoid from being 100% efficient (neglecting friction)?. I've found lots on the internet about efficiencies of electric motors, but not solenoids. Any help is appreciated.

 

[electricpete]

Yes, friction would be a source of losses. Even if you neglect friction losses, there are resistive losses.

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[electricpete]

Also for ac solenoids (and to lesser extent dc solenoids during transients), there will be iron losses (hysteresis and eddy current.

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[itsmoked]

You also have wire resistance losses.
And at high speeds windage losses.
The spring would have losses.
Any noise made is a loss.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[dbaird]

Most solenoid manufactures list the "response time" of their solenoids. That time comprises of:

Pull in Time (Actuation Time)
The full time it takes from switch-on to the moment a linear solenoid completes its stroke, or a rotary solenoid has moved through its rotation angle. This includes the coil excitation time.
It is sometimes possible to reduce over all pull in time by over-exciting (over volting) the coil for a very short period (milliseconds).

Drop out Time
The total amount of time taken for the solenoid to return to its rest position after current is switched off. The drop out time will depend on the mass being moved and the influence of any springs.

Check page 512:

http://www.ascovalve.com/Common/PDFFiles/Product/Engineering.pdf

David Baird

Sr Controls Designer
EET degree.
Journeyman Electrician.

 

[Skogsgurra]

The reason you do not find any data on efficiency of solenoids is that it cannot be defined in any meaningful way.

What definition are you thinking of?

Way times force divided by electric energy would be one possible definition. But hardly practical, since energy is also needed to keep the armature after it has moved.


Gunnar Englund

http://www.gke.org

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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

 

[waross]

As Gunnar says, the losses inherent in a solenoid when it is holding are generally much greater than the energy to move the load. Even if the losses are not excessive, when the time to operate versus the indeterminate time sitting energized is factored in, efficiency becomes meaningless.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[OperaHouse]

Regardless of how you define efficiency, most are driven poorly. Current should be reduced once they pull in.

 

[engineered8]

Thanks for all of the info. I am actually thinking about using the solenoid in reverse--meaning i push the magnet through the coil and electricity is generated. I'm wondering if this would be more efficient than turning a generator (a motor in reverse) assuming both have the same power input.

 

[dpc]

I really doubt it because the solenoid is constantly accelerating and decelerating, not to mention stopping twice in each cycle.

You have a very small linear motor/generator. People working on wave energy are looking at these.

 

[waross]

Very few solenoids have a magnet. Most have an iron slug.
However you may still be able to convert some existing device.
Look for a small radial engine to use as a platform.
Remove the pistons and replace them with permanent magnets.
Remove the cylinders and replace them with coils of wire.
Finally remove the valves and replace them with diodes.
You will now have a direct current generator working on the principle of inserting magnets into coils.
There may be a few small mechanical details for you to work out during construction, but I am sure that the gurus here will vouch for the validity of the basic principles involved.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[itsmoked]

Millions of generators point to rotary motion being superior over reciprocating motion for generating power.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[Compositepro]

As Gunnar said, efficiency of a solenoid is really meaningless unless you define it in a very specific way. Solenoids are usually used as force generating devices and not to do work. When a solenoid is not moving it can generate force but is doing zero work so its energy efficiency is zero. In accelerating its core there is work being done on the core but that is not work tranfered to the load. So reciprocating solenoids are pretty inefficient at doing work unless it is a spring/mass system which behaves like a rotating load.

 

[hawkinsj]

I've not heard of solenoid efficiency before. It would seem to be required to relate to work efficiency in order to be meaningful at all.

Motor efficiency relates to power out/power in. This is tied to the actual work performed by the motor...in it's steady state of operation.

A statement of efficiency regarding a solenoid would seem to be related to it's work performed in moving whatever it moves from initial to final state. Thereafter (after it reaches its final state and begins to hold in), there is only a concern for consumption because no work is being done beyond that point.

 

[israelkk]

An alternative measure of a solenoid properties is "Pressure equivalent" where:
Pressure equivalent = Solenoid force / Armature section area

This way you can compare the solenoid as an actuator to a pneumatic or hydraulic actuator. The "pressure" that a solenoid can develop is ~6 atmospheres for very short stroke and is limited by the magnetic saturation of the iron.

Hydraulic or pneumatic actuators can use hundreds of atmospheres and more.

Therefore, for large force actuators even for very short strokes a solenoid will me much larger than pneumatic or hydraulic actuator.