RE: T/S Inertia

Page 8 of 9  

This is better with some resistance to absorb the energy. Without it the switch contacts usually burn off, quickly.
news:02510f27-22e4-4de7-afca-Electric brake -- short out the supply wires after cutting the power, and the motor forces itself to stop.
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"Father Haskell" wrote:

-------------------------------------- Two totally different things.
One is a disc brake that immediately clamps when power is removed and when stopped, holds the shaft in place.
The other is what is called dynamic braking.
Involves an electro/mechanical interlocked reversing motor starter with the reversing contactor contacts shorted together with a heavy duty bus bar.
The spinning rotor generates the back EMF and stops the motor, but does not lock the shaft in place.
You need a well made motor because of the very high mechanical stresses imposed on the stator.
Both are expensive, even for heavy duty machine tool applications.
Lew
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Electric brake -- short out the supply wires after cutting the power, and the motor forces itself to stop.
For an almost instant stop, I gather that something called DC injection is required and this requires a special and expensive motor.
Jeff
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Jeff Gorman, West Yorkshire, UK
email : Username is amgron
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Not true.
I worked with many different dynamic and mechanical braking systems, including DC Injection braking and none were any special motors. OTOH these were industrial applications using larger HP units.
Geeeeez. My cheap $189 slide saw has dynamic braking on it and I doubt it is any special motor. The blade had to worth half the price. It also has a delay circuit that doesn't react immediately.
wrote Electric brake -- short out the supply wires after cutting the power, and the motor forces itself to stop.
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That's why I'm surprised higher end table saws don't use dynamic braking. The controller is a lot more complicated (expensive) than a slider's. It doesn't seem like much of a stretch to add a couple of contacts to it.
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As a side benefit, you can put the generated energy back in the grid and recoup some of the electric cost of running the saw. *grin*
Puckdropper
--
Never teach your apprentice everything you know.

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The cost of the dual register meter would break even in how many decades? LOL
"Puckdropper" <puckdropper(at)yahoo(dot)com> wrote in message

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The meter is free. Unless there is something intentionally installed in the meter, all will run backwards if the energy goes the other way. The hardware needed to sync to the line, OTOH,...
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Now that would depend on the area you are metered by.
LOL @ sync

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Which drugs are you on today?
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How many different nicknames do you go by in these groups?

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None. I always use my real name. I do have two accounts, one Google (used when no NNTP access is possible), one not.

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Maybe stick to valid topics?

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Wow, Captian PKB speaks. BTW, Is this supposed to make sense in this thread?

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I don't know. Why did you bring up drugs and attempt to roll the topic?

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You don't know if you're trying to make sense? Well, I guess that says it all. You are nothing but a troll.

Maybe because I'm truing to figure out if you're on drugs or just stupid. I've come to the realization that the choices aren't exclusive.
Maybe you can find someone else who will talk to you now. You're sure limiting your possibilities quickly.
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If you would have used Doug's killfilter list you would have killfiltered me before I posted at all. Obviously you don't follow orders well.
Now run along and play with the other OCD boys. Maybe they can tolerate your nonsense.
You don't know if you're trying to make sense? Well, I guess that says it all. You are nothing but a troll.
Maybe because I'm truing to figure out if you're on drugs or just stupid. I've come to the realization that the choices aren't exclusive.
Maybe you can find someone else who will talk to you now. You're sure limiting your possibilities quickly.
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"Jeff Gorman" wrote:

My previous post INCORRECTLY described "Regenerative braking" as "Dynamic braking".
Dynamic braking still requires a set of interlocked contactors which very much look like a reversing motor starter which is used to apply a DC voltage to the motor windings.
You need a DC power supply and a time delay relay to accomplish dynamic braking.
Take your choice, a motor mounted disc brake, a regenerative braking or a dynamic braking approach.
All are expensive, have lots of control hardware and are used on 3 phase motors.
It is totally cost prohibitive for a single phase motor.
Lew
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Do you have any references for that statement?
We were always informed that regenerative braking was just another type not using an external stimulus.
No interlocking contactors are needed for regenerative braking. My first chop saw used a SPDT switch in the handle. When you let go the motor got shorted out. It's that circuitry simple. The switch doesn't last long, as no ballast load is supplied to limit the arcing current when this happens. The blades stopped very quickly, though.
My previous post INCORRECTLY described "Regenerative braking" as "Dynamic braking".
Dynamic braking still requires a set of interlocked contactors which very much look like a reversing motor starter which is used to apply a DC voltage to the motor windings.
You need a DC power supply and a time delay relay to accomplish dynamic braking.
Take your choice, a motor mounted disc brake, a regenerative braking or a dynamic braking approach.
All are expensive, have lots of control hardware and are used on 3 phase motors.
It is totally cost prohibitive for a single phase motor.
Lew
"Jeff Gorman" wrote:

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wrote:

"Regenerative" is simply "dynamic" with the energy recovered ("re-generated").

You don't need to apply a DC current. A short will do. The back-EMF provides the braking energy. DC will stop it even faster, though.

No, a simple switch will work.

Nah, there's nothing special about a three-phase motor that allows dynamic braking.
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