Is it feasible for E-stop to be wired directly to a variable speed drive? Or should an E-stop be wired to a contactor that sits between power supply and VSD?

 

It is only feasible to wire an e-stop to the VSD if the drive complies to the relevant regulations, otherwise no. Mainstream drive manufacturers are now adding safe off functions that can be used for safety applications. We have used the Rockwell system on both Powerflex 700 and 70 drives. The 70 uses a simple module which is easily fitted.

On others we have used contactors before or after the drive, depends on the drive and the manufacturers recommendations.

 

You'll have to be a little more specific about your circumstance to answer that. If all you need to do is "remove power" then you can certainly simply let the e-stop interrupt the contactor's coil and let the contactor drop out. Lots of conveyor chains - among other things - are wired this way.

But if the motor coasting down is likely to let a load fall that crushes someone's hand, or some other bad things, then you may need for the e-stop to initiate some kind of active braking or reverse to retract, in which case the VFD will need it's power to do those.

Alternately, you might be able to let the e-stop control both the VFD power and some kind of brake unit.

There's a lot of "possible" situations to assess, and you need to look at them and do what's safe for your situation. Without a good understanding of your application that question is too open ended.

MB

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Hi,
What is the risk category of the machine?
Do you need to CE mark the equipment?
Is the machine part of a larger installation?
How does the VSD manufacturer recommend E-Stopping the drive?
Are there other drives or motors on the machine needing E-stops?

Marc

 

The drive is used to control a motor on a pump so there is no special breaking required I just want to remove the power from the field in the event of an E-stop being activated. The drive is an ABB ACS800 series drive.

 

Depending on the regulations you need to comply with will depend on how you handle this, along with the recommendations from the manufacturer. By determining risks and exposure will determine a the level of protection, using guides and regulations.

If you use a contactor before or after the drive look at using a safety relay with an off-delay timed contact to control the drive contactor, and used an instantaneous contact for the drive enable. With supply side contactors, add a timer to ensure there is adequate power down on the drive before power is re-applied.