adccommunitymod (AutomationDirect) asked a question.
Created Date: October 06,2016
Created By: sauger
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Using a Marathon 3 phase motor and it has two Protection leads. They are basically a continuous wire with some thermal switches inline. In the event of a thermal overload, the continuity of the wire is broken. I can figure out how to wire it into my Minarek controller to stop the motor, but what I'm having a hard time finding is a way to latch the circuit shut until another switch is pressed. I don't want the motor to just turn back on when it cools down. Effectively, it would be a circuit breaker, but instead of tripping when you draw too much current, it would trip when you lose signal and need to be manually reset. Appreciate any help or leads on this.
Created Date: October 06,2016
Created by: sauger
Using a Marathon 3 phase motor and it has two Protection leads. They are basically a continuous wire with some thermal switches inline. In the event of a thermal overload, the continuity of the wire is broken.
I can figure out how to wire it into my Minarek controller to stop the motor, but what I'm having a hard time finding is a way to latch the circuit shut until another switch is pressed. I don't want the motor to just turn back on when it cools down. Effectively, it would be a circuit breaker, but instead of tripping when you draw too much current, it would trip when you lose signal and need to be manually reset.
Appreciate any help or leads on this.
Created Date: October 07,2016
Created by: Cow
You didn't state how this motor is controlled? Start/stop buttons, on/off switch or ...?
With start/stop buttons I always use the starter aux contact to send a run signal to the plc to keep the starter coil engaged. I would put this thermal overload switch in series with the aux contact run signal.
With an on/off switch, I'll use a timer with a short time delay(500 ms) to allow the starter to pull in before relying on the run signal I'm getting from the aux contacts to keep it engaged. Again, I'd put the thermal overload switch in series with the run signal.
Created Date: October 10,2016
Created by: sauger
It's a 3 way toggle, Fwd, Off, Rev. The problem I have with putting the thermal control line in series with the run signal is that, if my operator doesn't put the machine in the off position on a thermal fault, the belt will just fire back up as soon as it cools down. I wanted to make sure that I have something that they have to do to turn it back on (like the breaker reset switch on most motors).
My current plan is to set up a self-latching relay with the temp controller as an unlatching switch. This will run a 2nd relay that will disconnect/reconnect the enable wire for my controller. If one of the switches in the thermal protection switch opens, the relay will unlatch and open the enable circuit on the controller.
Created Date: October 15,2016
Created by: andremholmes
if you use a toggle switch it will restart unless you are using a vfd and set it up so you have to switch it off then on to run again. You have to use start/stop buttons with a latching relay and thermostat in series.
Created Date: October 15,2016
Created by: ControlsGuy
Yes, you could change from the selector to a three-wire magnetically held start circuit (plus direction selector switch), which would have the advantage of also preventing the motor from unexpectedly restarting after a power failure.
If you want to keep the selector for motor control, then instead latch the overtemp condition. Make and latch a relay and display the condition with a pilot light. Interrupt the latch leg (NOT the main leg with the temp switch) with a normally-closed pushbutton contact marked "Reset " or something. Then put an NC contact of the fault latch relay in series with the run signal.