E-Stop wiring help

[jwalter]

I have a machine that uses 220 volt to drive a motor which runs off a powerflex drive. There is an estop switch that runs through a 120 volt contactor. My 220 circuit includes 3 hots & ground. There is no neutral. I was told by the electrician that it is not safe to use one leg of the 220 without a neutral. I have not found many options in a flex drop cord that includes 5 wires, plus since my original 220 run also did not have the extra conductor, I am thinking that this is not a common way to set this up. It may be easier to change out the contactor. What is the correct way to pull 110 from a 220 circuit? What is the correct way to set up this estop? thanks

[RussB]

1. Through a transformer. 2. Through a "Safety Relay".

[jwalter]

Thank you for replying. So with a safety relay, would the coil be energized from the 24volts of the VFD? Thanks

[jwalter]

I wanted to update this post with a schematic that I drew of the system. I am looking for help in changing this to work on a wiring system that does not include the neutral on the 220 feed input. I highlighted the line in red. I realize the relay uses a 110v coil, but I could replace that with another type, possibly a 24volt. I was thinking that I could pull the 24v output from the powerflex but wasnt sure if that would work right. If not anyother ideas? Thanks

[panic mode]

your circuit is not clear, what exactly is in the circles? there are 4 wires going to "momentary power", what exactly is this - two contacts, contact and lamp or something else? where is schematic? about power: in the past this would be solved by using 2-pole CB or fuses and add small isolation transformer (110VAC or 24VAC). one side of secondary would be grounded and you don't need neutral. today I would do exactly the same thing but use a small 24V switching mode power supply (one with universal AC input such as 90-250V) which could be then powered from two phases directly. in this case you would not need a transformer of neutral and your control circuit is DC. about the e-stop circuit: to be an emergency stop circuit, it should provide means of isolating power (which it does not, you only manipulate control signals, there is nothing between circuit breaker and power flex). but killing power to the drive would also kill the 24V and that means your estop circuit would not be able to operate. I would use something like: http://www.bannerengineering.com/training/subtopic.php?topicID=P8_02_020 or http://sccatalog.honeywell.com/imc/printfriendly.asp?FAM=safetymodules&PN=FF-SRT011R2