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Freewheel Stop


chaterpilar

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Some soft starters, in this case your ATS48, can be connected "inside the delta" of a Y-Delta wound motor. The motor is started and run as a Delta motor, but by taking advantage of the Y-Delta 6 wire connections, the soft starter can be wired within the Delta windings. This means that the soft starter need only be rated for 58% of the motor full load current since some of the power will be supplied directly to the ends of the connections (you really need to see it on a diagram to understand). Reduction of the current rating of the soft starter is the ONLY advantage to doing it this way, there are a lot of disadvantages.

 

One of the disadvantages is that you CANNOT use any DC Injection braking feature of a soft starter because you cannot apply DC to only 2 of the windings in this configuration, which would be one reason why they would make that comment.

 

However I don't see why you couldn't use the Decel Ramp feature, that would not have any limitation that I can see by being connected inside the Delta. No other soft starter manufacturer that I know of who offers an 'inside the Delta" configuration has that kind of restriction.

 

So it is either something peculiar to the ATS48, or possibly a translation error from the original French, where they meant to say BRAKING is not permissible. Only Schneider could answer that question for sure.

 

If you are no using the soft starter connected inside the Delta, none of this applies to you.

"He's not dead, he's just pinin' for the fjords!"
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It all depends on the algorithms and software that they have written.

It is possible to have DC braking within a delta connection, but it is a totally different algorithm to the standard three wire connection. Similarly, it is possible to have soft stop within the delta connection, but it requires a different algorithm. The soft start is easiest and can use similar routines to the standard soft start with a few parameters changed.

I suspect the issue is that they have not perfected "inside delta" algorithms and software at this stage.

 

Best regards,

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Thanks for that tidbit Mark. So really, you can do DCIB inside the Delta?

 

Some day you and I need to design the "perfect soft starter". Probably won't sell because it would be too expensive, but we would have the satisfaction of knowing it could be done!

"He's not dead, he's just pinin' for the fjords!"
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JRaef,

 

Consider that a VFD, with DC injection braking, doesn't ask .... and doesn't care

 

whether the motor is Delta or Star connected.

 

 

Here's a question for you,

 

For a given value of dc current, which configuration —Star ? or Delta ? —develops more braking torque per dc ampere? or, are they equal ? ....... and WHY ?

 

Lest your thinking go off on the wrong tangent, consider that each motor is
internally
connected into its respective configuration, with only three leads brought out.....

 

 

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Hi Jraef

Some day you and I need to design the "perfect soft starter"

I started a thread along those lines some time ago to see if there were any ideas out there, and there have been no replies to date. - everyone must be happy with what they have!!

 

http://www.lmpforum.com/inforum/index.php?showtopic=463

it would be too expensive

Not so sure about that, except that the one start per hour at 300% current,start an open shaft motor only type units are always cheaper to build, but false economy in the long run.

 

Have a god day,

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JRaef,

 

Consider that a VFD, with DC injection braking, doesn't ask .... and doesn't care

 

whether the motor is Delta or Star connected.

Here's a question for you,

 

For a given value of dc current, which configuration —Star ? or Delta ? —develops more braking torque per dc ampere? or, are they equal ? ....... and WHY ?

 

Lest your thinking go off on the wrong tangent, consider that each motor is
internally
connected into its respective configuration, with only three leads brought out.....

JOmega,

I wasn't actually referring to the motor being Star or Delta connected, but to the Soft Starter being connected INSIDE the Delta.

 

If the DCIB were connected outside as they normally are, off the top of my head I don't see why the braking torque per amp DC would be any different. The braking torque is dependant on the square of the current. At a given braking VOLTAGE I can see them being different because you would get a lower amp flow in Star, but amp for amp, why would the torque be different? I generally don't concern myself with the internal motor connections since we don't really use the 2 voltage levels they would represent here. Something tells me I'm about to get some new info however! :P

"He's not dead, he's just pinin' for the fjords!"
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JOmega,

X---------------------------------- snip ---------------------------------------X

 

Something tells me I'm about to get some new info however! :P

 

Hi Jeff,

Sorry for dely; I'm working on graphics for explication. Should post reply by end of week.

 

 

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