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How many batteries

14skipper

By 14skipper
in Boat Equipment

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Robin2 Rising Star

Robin2

Posted
Posted

I never suggested they did. You were querying why AC motors were less efficient than DC and a quick Google threw that up.

 

Tony

The web page you referred to is about the efficiency of control systems !

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smileypete Veteran II

smileypete

Posted
Posted (edited)

The web page you referred to is about the efficiency of control systems !

OK...

 

What do DC motors have that AC motors don't?

What does this do?

How is this provided in AC motors?

What does providing the same in AC motors entail?

 

cheers,

Pete.

Edited by smileypete
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Robin2 Rising Star

Robin2

Posted
Posted

OK...

 

What do DC motors have that AC motors don't?

What does this do?

How is this provided in AC motors?

What does providing the same in AC motors entail?

 

cheers,

Pete.

 

You are not being very helpful!

 

Are you auditioning for the job of quizzmaster?

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Gibbo Veteran II

Gibbo

Posted
Posted

What have magnets got to do with it?

 

You're not making much progress here are you!

 

Most low to medium power DC motors have permanent magnets. Most AC motors have electromagnets. So before you even do anything flash like making the rotor spin round, the AC motor instantly has an efficiency disadvantage because it has to use power to make some magnets.

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Robin2 Rising Star

Robin2

Posted
Posted

You're not making much progress here are you!

 

Most low to medium power DC motors have permanent magnets. Most AC motors have electromagnets. So before you even do anything flash like making the rotor spin round, the AC motor instantly has an efficiency disadvantage because it has to use power to make some magnets.

 

I hope you are not suggesting that magnets supply energy !

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Gibbo Veteran II

Gibbo

Posted
Posted

If they don't supply energy (and they don't) how could magnets improve efficiency?

 

Jeez...

 

A motor needs magnets to operate. The electromagnet then has something push against. That's how motors work.

 

In most small DC motors, those magnets are permanent magnets. In terms of energy they are free, they don't use any energy.

 

In AC motors they are electromagnets. In terms of energy they are not free, they use energy.

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Robin2 Rising Star

Robin2

Posted
Posted

Jeez...

 

A motor needs magnets to operate. The electromagnet then has something push against. That's how motors work.

 

In most small DC motors, those magnets are permanent magnets. In terms of energy they are free, they don't use any energy.

 

Sounds like it would be a good idea to replace the coils on the armature with permanent magnets also !

 

In AC motors they are electromagnets. In terms of energy they are not free, they use energy.

 

They only consume energy due to heating losses in the coil. If you had superconductors they wouldn't use energy.

 

If we start discussing the practical inefficiencies in different types of motor the list for DC motors will be as long as for any other type.

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Gibbo Veteran II

Gibbo

Posted
Posted (edited)

They only consume energy due to heating losses in the coil.

 

Do they really?

 

Oh, and here was silly me thinking they used energy to overcome hysteresis losses and eddy current losses in the core. Both of which I thought should be equally balanced with the resistive losses in a correctly designed motor. I also thought there were hysteresis and eddy current losses in the surrounding metalwork.

 

But what do I know? Thank you for educating me.

 

If you had superconductors they wouldn't use energy.

 

Again, really?

 

Silly old me thought you could only build a lossless superconducting electromagnet with DC.

 

I'm learning so much from you tonight.

Edited by Gibbo
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Robin2 Rising Star

Robin2

Posted
Posted

Do they really?

 

Oh, and here was silly me thinking they used energy to overcome hysteresis losses and eddy current losses in the core. Both of which I thought should be equally balanced with the resistive losses in a correctly designed motor. I also thought there were hysteresis and eddy current losses in the surrounding metalwork.

 

But what do I know? Thank you for educating me.

 

 

 

Again, really?

 

Silly old me thought you could only build a lossless superconducting electromagnet with DC.

 

I'm learning so much from you tonight.

 

I'm delighted. Let me know if I can help some more.

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Alan Saunders Rising Star

Alan Saunders

Posted
Posted
Hi l expect this has been asked before but how many batteries should you need to have on a liveaboard ? :wacko:

You need none! Hand-start the engine, use heat from the engine for hot water. Use paraffin, diesel, wood, coal, gas, candles etc for cooking, heating, light, maybe an acetylene 'tunnel' lamp.

 

If you must have electrical devices, do an audit (is there an echo here?).

 

How long will you run the engine each day? If you go to work every day and stick to the 8am to 8pm rule you will need sufficient capacity to last between weekends. If you are retired you could run your engine for 12 hours every day.

 

If you have a land-line connection you may be able to run everything from that.

 

Play the game, answer the questions!

 

Alan

(~1968 - did some calculations for the first 'practical' UK superconductive motor, pump motor in a submarine. Still not practical.)

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blodger Rising Star

blodger

Posted
Posted (edited)

You need none! Hand-start the engine, use heat from the engine for hot water. Use paraffin, diesel, wood, coal, gas, candles etc for cooking, heating, light, maybe an acetylene 'tunnel' lamp.

 

If you must have electrical devices, do an audit (is there an echo here?).

 

How long will you run the engine each day? If you go to work every day and stick to the 8am to 8pm rule you will need sufficient capacity to last between weekends. If you are retired you could run your engine for 12 hours every day.

 

If you have a land-line connection you may be able to run everything from that.

 

Play the game, answer the questions!

 

Alan

(~1968 - did some calculations for the first 'practical' UK superconductive motor, pump motor in a submarine. Still not practical.)

I agree with the above; The OP had all the answers it was feasible to give before

the thread wandered into other territory :blink:

Edited by blodger
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WotEver Veteran II

WotEverDonate to Canal World

Posted
Posted

Sounds like it would be a good idea to replace the coils on the armature with permanent magnets also !

Silly designers, why ever didn't they think of that?

 

Auto-flipping power-free permanent magnets - now there's a concept ;)

 

Tony

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sebrof Rising Star

sebrof

Posted
Posted (edited)

Nope, can't be that. A joke has to have humour in it.

 

Try again - it's good to see you exercising your brain in this way. Does it give you a headache?

 

Tony

[/quote

 

 

You're right. It's a sort of mental limbo dancing, trying to get down to your level. So far I'm about twenty thousand leagues under the sea, but still have quite a long way to go.

Edited by sebrof
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