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Topic Title: 5 5.5kw table saw with star delta manual c/o switch braking options.
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Created On: 09 February 2019 03:07 PM
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 09 February 2019 03:07 PM
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hertzal123

Posts: 503
Joined: 26 August 2007

I have been asked to fit an automatic brake to the above 400v saw to stop it in less than 10s.An all in one s/d starter and brake has been suggested by a supplier,but wondering if a dc brake module could be wired into the existing setup at a considerable saving,since the s/d changover is already operated by a rotary switch.Thanks for any advice.Hz
 09 February 2019 03:43 PM
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Dave69

Posts: 789
Joined: 16 July 2011

A 55.5kW motor seems a bit much for a saw, what the heck is it cutting?
Why the 10 seconds? By that time it will have done its damage. Injecting dc could stop the motor almost dead but it may well break its mountings
 09 February 2019 04:50 PM
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alancapon

Posts: 7492
Joined: 27 December 2005

Do you really mean a 55.5kW motor for the table saw? The quickest method of stopping it would be dc injection, but as Dave69 says you need to make sure you don't stop it too fast, or it is liable to turn over where it stands.

Regards,

Alan.
 09 February 2019 04:56 PM
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mapj1

Posts: 12039
Joined: 22 July 2004

ten seconds comes from advice of the machinery directives, but relates to situations where blades are guarded, and the assumption is that it takes up to ten seconds to get the guard up. normally big things where it cannot safely be stopped dead. Not a 'normal' table saw. There are also systems that drop blades out of the way using the momentum to do that.

-------------------------
regards Mike
 09 February 2019 05:26 PM
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paulskyrme

Posts: 1364
Joined: 12 February 2003

The 10s does mapj1, but, it is carried through to PUWER requirements in HSE guidance.
In the same vein that it would be expected to update a fixed installation in compliance with the latest version of BS7671, the same requirement applies to machinery.
So EN 60204-1 & ISO 13849-1 & -2 would be the starting point as the DC brake is a safety function, and it is also a safety device placed on the market independently so it must be CE marked in full in its own right and come with full integration instructions.
 09 February 2019 05:47 PM
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hertzal123

Posts: 503
Joined: 26 August 2007

Sorry for the typo,should be 5.5Kw,Clamped at 12A while in use.
Regards,Hz
 09 February 2019 06:06 PM
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hertzal123

Posts: 503
Joined: 26 August 2007

So basically,it may be safer to fit a custom made auto sd starter with brake rather than trying to modify the existing setup with just a brake module?
Regards Hz
 09 February 2019 07:22 PM
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paulskyrme

Posts: 1364
Joined: 12 February 2003

You'll have a job updating the current to meet PLc for an e-stop function I would expect, so yes.
Mind, like compliance with BS7671 it's not compulsory, you can do whatever you like, same as you can with building wiring, but, if you don't follow the standards you would be expected to be able to demonstrate that what you have done is as safe or safer than if you had utilised the standards.
Can you do that with modifying the old kit, it would be difficult to do the ISO 13849-2 analysis on used equipment, especially if the relevant data is not available, and without that how are you going to prove that the safety function is safe enough for example.
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