Use of Proper Motor Controllers

[wireman]

This may need to be posted under the Saftey section, but I'll start with it here instead. It may get read more in this section.

Anyway, lets say you have a conveyor controlled by a motor starter with an E-Stop PB. Does anyone put one 3P contactor in series with a 3P motor starter to meet safety requirements to minimze risk in the event of failure (ex: see NFPA-79 Annex H.2). This statement in the NFPA says to include circuit design to reduce the possibllity of failures causing undesirable operations. It also say you could use devices w/positive-opening operation (force-guided contacts)

Offhand does anyone know if standard Allen-Bradley or GE motor starters use force guided contacts. It will be hard to compete if everyone else is bidding with only one motor starter and I'm using a contactor AND a motor starter.

=======
thanks.

 

[jim dungar]

Offhand does anyone know if standard Allen-Bradley or GE motor starters use force guided contacts. It will be hard to compete if everyone else is bidding with only one motor starter and I'm using a contactor AND a motor starter.

I know of no "standard" motor starter that has force guided power contacts. Most safety power circuits I have seen employ standard contactors in series.