I thought they fired me.

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Last I saw that mill it was an ATL with current sensors, PLC control and interlocks to prevent plugging. I would guess it was about 3-4 seconds. I declined their offer to let me bid the new control. Obviously no body else wants that privelage.

Anyone here want to take on the prpject?
 
It's common to have Shunt Trip on breakers feeding Soft Starters, because if the SCRs short, that it the only way to kill power; without it you can lose the motor by allowing single phase power to flow to it without restriction (like welding the contacts). So most soft starters have Shorted SCR detection and a relay that you wire to the ST on the breaker. In some soft starts, that is a separate relay, in others it is a general Fault Relay, so any OTHER fault besides a Shorted SCR will have the same effect. Schneider has different version of their soft starters, the cheaper ones (ATS22) do not have the differentiation. So if the motor was plugged up and not turning, that would cause a Trip and that would engage the Shunt Trip immediately.
 
Jraef said:
It's common to have Shunt Trip on breakers feeding Soft Starters, because if the SCRs short, that it the only way to kill power; without it you can lose the motor by allowing single phase power to flow to it without restriction (like welding the contacts). So most soft starters have Shorted SCR detection and a relay that you wire to the ST on the breaker. In some soft starts, that is a separate relay, in others it is a general Fault Relay, so any OTHER fault besides a Shorted SCR will have the same effect. Schneider has different version of their soft starters, the cheaper ones (ATS22) do not have the differentiation. So if the motor was plugged up and not turning, that would cause a Trip and that would engage the Shunt Trip immediately.
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ptonsparky said:
Help told me this afternoon that when the SS display hit 500 amps it showed a Fault message and the breaker tripped.
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Question, does soft start clear the fault message on power off? If so seems it could make more difficulty for troubleshooting as you wouldn't know the reason for trip as easily, unless it also has fault logging ability.
 
kwired said:
Question, does soft start clear the fault message on power off? If so seems it could make more difficulty for troubleshooting as you wouldn't know the reason for trip as easily, unless it also has fault logging ability.
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Again, it depends on the unit. Cheaper ones do clear the fault on power down, more expensive ones allow you to program whether or not you want that to happen. Ironically, it’s often also the more expensive versions that come with a fault history. When people opt for the cheapest soft starter available, it’s these little details they are sacrificing and you don’t know their value until you need them.
 
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