Can you slow down a axial generator by cutting the flow of the power been generatored and then putting a current back into the generator to stop it

Thread Starter

Berserkhealr

Joined Jul 28, 2021
7
I am sure axial are used in wind turbines so i will use it as my example.

Say you are using the wind turbine to generate power but its getting to windy and you want to slow down the turbine to bring it to a stop.

What i want to know is ...

If you can cut off the power thats been generated, to then have power inputted into the generator from another sauce would this then act as a type of electromagnetic and use this to help slow down the turbine to bring it to a stop and hold it in place?
 

Thread Starter

Berserkhealr

Joined Jul 28, 2021
7
Hey, thanks for the link. If anything what im looking at is the other way round... i would be using power to break... i want it so when i put power back into the motor / generator it would then slow down the moving part... acting like an electromagnet to which would be the break. Can this be done?
 

Externet

Joined Nov 29, 2005
1,654
It would be preferred to apply power to a solenoid actuated brake. Perhaps it would make more sense by braking when power is removed, and releasing when energized. Implementing feathering the blades is more complex. Turning the whole turbine 90 degrees is another way. Pulling a rope on the mast to actuate or release friction brakes is yet another.

----> https://www.easternmarine.com/trailer-brakes-electric
 

Audioguru again

Joined Oct 21, 2019
3,513
You want to brake the generator, you do not want to break the generator. A HUGE difference.

Adding power to a generator obviously makes it spin faster. To slow the generator then you must add a load or an overload to slow it.
Maybe the vanes on a windmill can be turned for less pitch so that they are pushed less by the wind like some airplanes propellers (feathered).

My model airplanes short the motor (a heavy load) to prevent its propeller from acting like a windmill when the throttle is zero.
 

Thread Starter

Berserkhealr

Joined Jul 28, 2021
7
Thank you for the reply. I am just using the turbine as an example. I dont want to add or use anything, or other ways of slowing it down. I just want to be able to slow down and stop the ' turbine ' from moving but only with the generator. Is this possible?
 

Thread Starter

Berserkhealr

Joined Jul 28, 2021
7
You want to brake the generator, you do not want to break the generator. A HUGE difference.

Adding power to a generator obviously makes it spin faster. To slow the generator then you must add a load or an overload to slow it.
Maybe the vanes on a windmill can be turned for less pitch so that they are pushed less by the wind like some airplanes propellers (feathered).

My model airplanes short the motor (a heavy load) to prevent its propeller from acting like a windmill when the throttle is zero.

So if that is the case, say if its spinning clock wise can you then send a voltage from the opposite side to then slow it acting as a break. Then to hold it in place have the same current coming from the other side to hold it in place?
 

Externet

Joined Nov 29, 2005
1,654
Short circuiting a generator output should do the trick; if its wiring/windings do not explode from extreme currents resuming speed again. Experiment with a toy and think about a large scale one. :oops:
 

Thread Starter

Berserkhealr

Joined Jul 28, 2021
7
Short circuiting a generator output should do the trick; if its wiring/windings do not explode from extreme currents resuming speed again. Experiment with a toy and think about a large scale one. :oops:
Yeah i did think of something along these lines and having some sort of a resister switch to control how strong the short circuit would be.
 

MrChips

Joined Oct 2, 2009
24,180
What you have in mind is partially correct.

If you short the windings of the generator it presents an infinite load which will retard the motion. To decelerate more quickly you would have to apply a negative resistance, i.e. increase the current flow, not decrease it.
 

MisterBill2

Joined Jan 23, 2018
9,267
Short circuiting a generator output should do the trick; if its wiring/windings do not explode from extreme currents resuming speed again. Experiment with a toy and think about a large scale one. :oops:
I have had several mains operated electric rotary mowers and theytend to short circuit the drive motor to stop it quickly when it is switched off. That short term overload destroyed the first one and so I disconnect that feature now every time I get another mower. The do wear out after a while, but the mains powered ones perform better than the battery powered ones.
 

Ian0

Joined Aug 7, 2020
3,232
Just installed a 1kW wind turbine, and the controller uses two triacs across the three phases to stop it if things are getting too windy. I didn't investigate if they were phase-fired to slow it down gently. The old version used a contactor.
If you wanted to stop it using its own power and keep it stopped use a magnetically latched contactor. Then send a pulse of the opposite polarity to the contactor to restart it.
 

Audioguru again

Joined Oct 21, 2019
3,513
On the internet they say that shorting a motor slows it down but does not stop it. At a low speed it generates a low current that is too weak to hold it stopped if an external force (the wind) turns it. Try it to see if it slows enough.
 

MisterBill2

Joined Jan 23, 2018
9,267
Shorting a decent generator will make it a lot harder to turn, but not keep it fully stopped like a mechanical brake will. The reason that I would avoid doing it is because of the power that a strong wind will deliver. That would keep running the generator into a shorted circuit, probably leading to over heating and burning out. A mechanical broke and a system to turn the direction to the least effective angle is safer for the generator. OR disengage the generator drive and let the prop freewheel, if it can stand the speed. Or use a prop-pitch control to flatten the blades.
 

Ian0

Joined Aug 7, 2020
3,232
OR disengage the generator drive and let the prop freewheel, if it can stand the speed
Most small turbines have the blades attached to the generator shaft. It generally can't stand the overspeed - which is the main reason for braking it during strong winds. Overspeed usually leads to the destruction of the motor (the magnets part company with the stator)
 

MisterBill2

Joined Jan 23, 2018
9,267
That is why Iadded the qualfier "if it can stand it". There are arrangements that turn the blades so that the wind does not catch them very well.. And on the really big wind turbines they can adjust the pitch of the blades.
 

Thread Starter

Berserkhealr

Joined Jul 28, 2021
7
Sorry for late reply, thanks all that answered me.

Say if you have due coils, so a line of coils each side of the magnets... will this help with the breaking and over load? And is there any way to help the over load?
 
Top