Does anybody know if i can wire a 2 wire normally closed emergency stop to a 3 phase 415v bench drill for operator safety.The contactor make is telemanique with no drawings,there are contacts 95&96 normally closed terminals with internal wires and normally open contacts 97&98 with no internal wiring.I have seen drawings for 2&3 wire remote start/stops but none for emergency stops.Can i wire the stop direct to the contactor or will i have to wire in a remote start/stop and come off this with an emergency stop to stop the bench drill?

justajiffy,
If there is already a stop button mechanism on the motor starter, it's just a matter of wiring the external E-stop button mechanism in series with the stop button on the starter.
Hope this helps.

I have a Danfoss instruction sheet that shows it in diagrams,
http://www.gideon.e7even.com/danfoss.png

It shows the stop button in series with the supply to the start/auxiliary switch, but it makes no real difference.

Gideon

Yeah,
That's correct.
All it does is opens the control circuit, which causes the hold-in contact to drop out and de-energise the contactor coil.

justajiffy, I assume that this might be in an industrial / commercial setup. If so do be sure that someone has done a risk assessment on the use of the equipment and that any mods you choose to do meet with PUWER 1992 (Provision and Use of Equipment Regs 1992. If you modify it and someone gets hurt in an incident you could be out on a limb. Reasd the HSE guidance notes and check with your Liability insurance its a wicked world out their now with industrial injury claims. Mike and Gideon are correct you can put as many stops in series as you feel are necessary. Regulation 16 deals specifically with Emergency Stop Controls Guidance note 167 states that E/Stops are intended to effect a rapid response to potentially dangerous situations and they should not be used as functional stops during normal operation.
168 states E/stop controls should be easily reached and actuated. Common types are mushroom-headed buttons, bars,levers,kick-plates,or preasure-sensative cables. Guidance on specific features of emergency stopsd is given in national and international standards (BS EN 292, BS5304, prEN418, and BS EN 60204-1). Good Luck and do take the time to have a look at the regs before you committ yourself.

Alan,
Very good call on the safety aspect of the Stop switch.
To have an E-stop fail when it is required to do it's job, is just un-thinkable.
At least if the wire feeding or coming from the E-stop break, the machine will stop.
Thing that worries me about the contact blocks that make up E-stop switches, is if they tend to be used as a means of turning the machine off as part of the operation of the machine, the actuator spring can weaken or in some cases break, therefore preventing the contacts from opening.
In a real emergency, I'd hate to be using that machine.

Do any manufacturers make E-stop units where the button physically operates two independent N/C switch sets which could then be wired in series as a double safeguard?

Do any manufacturers make E-stop units where the button physically operates two independent N/C switch sets which could then be wired in series as a double safeguard?
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Paul, Yes, all manufacturers do and you should be using them on systems in conjunction with a safety relay. This monitors the stop circuit for short circuits try looking at Telemecanique components catalogue under components for safety applications. Most modern equipment comes with a monitored E/Stop system fitted. It limits the possibility of being able to use the equipment with faulty guard switches and e/stops There is a host of preventa relays and applications listed in the telemec catalogue well worth having on the shelf. Sorry I dont have a web link to hand

Paul,
Most of the Schneider push-button actuators will take 2 contact blocks, as standard.
Personally, that's a rather good logical solution and one that I'd never thought of.
I've never trusted E-stops.