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Emergency Stop Controls For Vsd


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#1 munkey

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Posted 01 May 2009 - 07:13 PM

Hi there,

Some panels i have recently worked on have drawn a question.

Switch gear in these panels provide a start/stop and reference signal for inverters. The power supply for these inverters is through fuses directly from the main isolator.

When the estop is pressed, the control voltage is dropped out. But only the start/stop signal is lost not the power!

Can anyone offer any advice as to whether this is legal, and whether i should run power through a contactor that will break the supply.

Other problems are that these inverters drive shakers and pump which have to be brought to a controlled stop (ramp). Breaking the power will allow them to coast to a stop (uncontrolled)

Thanks

#2 jsl

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Posted 25 May 2010 - 12:37 PM

QUOTE (munkey @ May 2 2009, 03:13 AM) <{POST_SNAPBACK}>
Hi there,

Some panels i have recently worked on have drawn a question.

Switch gear in these panels provide a start/stop and reference signal for inverters. The power supply for these inverters is through fuses directly from the main isolator.

When the estop is pressed, the control voltage is dropped out. But only the start/stop signal is lost not the power!

Can anyone offer any advice as to whether this is legal, and whether i should run power through a contactor that will break the supply.

Other problems are that these inverters drive shakers and pump which have to be brought to a controlled stop (ramp). Breaking the power will allow them to coast to a stop (uncontrolled)

Thanks



it depends on the make type etc
the Schnieder altivar71 (and possibley other models) is tested and certified as a emergengy stop when wired and configured as per the schnieder drawing without having to use an disconnection device (contactor). this has been available for a few years now so i would assume other manufacterers have similar certification.

#3 elmger

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Posted 18 July 2010 - 07:28 PM

Whether an E-stop circuit is legal or not depends on how it is done, what jurisdiction the equipment is sold into and what regulation covers the completed assembly or machine. This is because the functional safety of the system is a different matter than the electrical or mechanical safety of the system.

As an example a coast to stop can be a good way to stop for a centrifuge if means are provided to prevent any person being hurt during the coast stop. However the same machine may be unsafe, and hence illegal, if a person can actually get hurt by the machine as it coasts down. The Machinery Safety Directive has direct application to machines and is a very good place to start to find standards on E-Stops.

All the best

Hamish

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