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Old July 12th, 2019, 06:08 PM   #1
Ones_Zeros
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Question Motor start timer after losing power

Hello
I have two 480v motors that has remote start capability.
When the remote start button is pressed the 1st motor starts in 15 seconds.
When the remote start button is pressed on the 2nd motor it starts in 30 seconds. I do this so they are not both started at the same time.

The issue that I’m having is if we lose the 480v power or blow a fuse, but
keep 110v power in the PLC panel because of a ups keeps it up. Then what happens is since the start Command was enabled on both motors before the power was lost, then they will both start after the 480v power is restored.

Is there any Logix that I could program into the PLC
that would prevent both motors from starting after
480v Power is restored? If this is possible could you
post examples?

I have a Allen Bradley 1769-L32E controller
I monitor the motor amps and vibration currently
In the plc. Could I use any of these?

I appreciate the help

Last edited by Ones_Zeros; July 12th, 2019 at 06:11 PM.
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Old July 12th, 2019, 06:22 PM   #2
James Mcquade
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Since you said you are monitoring the amps (assuming you mean all 3 phases),
you could program a latch bit for motor 1 and 2 - motor1 on / motor2 on.
in your logic I would say if the output is on and motor1 latch bit is on and any one of the phase currents for motor 1 drops below 1 amp (you didn't sat what hp so you could make it 5 amps if it is a 30 hp motor), then set a motor 1 power loss bit to turn off the motor 1 logic. only when the power is restored and you hit the start button for motor 1 will the system start the timer.

it's been a long and trying to go home.
just an idea I had and I hope this helps.

james
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Old July 12th, 2019, 09:51 PM   #3
willxfmr
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If the UPS is fed by a transformer off the 480, then you could use a simple cube relay on the line side of the power feeding the UPS. Line power energizes the relay, and a set of NO contacts go to the PLC to signal power loss. From there, you can use the input any way you choose. There are a bunch of power indicators available, but cube relays are cheap to install, and easy to replace.

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Last edited by willxfmr; July 12th, 2019 at 09:51 PM. Reason: Proof read... then post. Not the other way around silly.
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Old July 12th, 2019, 11:04 PM   #4
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What Willxfmr said. Years of similar issues taught me to ALWAYS have a “Commercial Power Available” bit, and if the pump station was also generator-backed, there was a “Generator Power Avaialble” bit. With those, the rest is easy.
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Old July 12th, 2019, 11:42 PM   #5
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as willxfmr said


+1
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Old July 13th, 2019, 04:15 AM   #6
janner_10
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Quote:
Originally Posted by willxfmr View Post
If the UPS is fed by a transformer off the 480, then you could use a simple cube relay on the line side of the power feeding the UPS. Line power energizes the relay, and a set of NO contacts go to the PLC to signal power loss. From there, you can use the input any way you choose. There are a bunch of power indicators available, but cube relays are cheap to install, and easy to replace.

Bubba.
This. Keep it simple.
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Old July 13th, 2019, 04:49 AM   #7
sparkie
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UPS's usually have a set of dry contacts on them, too.
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Old July 13th, 2019, 08:17 AM   #8
Ones_Zeros
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Thanks a lot guys
I appreciate the help
You have been very helpful

Thanks!
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Old July 13th, 2019, 09:03 AM   #9
Ones_Zeros
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would you guys recommend any specific cube relay for this type application?

thanks again
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Old July 17th, 2019, 10:47 AM   #10
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http://time-mark.com/shop/3-phase-monitors/257b/
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Old July 17th, 2019, 11:49 AM   #11
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With the motor amps you can detect if the motors are running, when they stop for any reason then signal the fault and reset the timers, the operator will have to press the button again to start.
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Old July 22nd, 2019, 01:30 PM   #12
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indeed check if running signal if not just rest the timers for any motor.
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Old July 22nd, 2019, 08:40 PM   #13
Ones_Zeros
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Since Im currently monitoring amps. How would be the best
Method to program this?

What I was thinking was if the amps go to zero
then de-energized a memory bit and start a timer to unlatch a bit to
Prevent startup.

Then when the 480v is restored the operator
would have to Press button to restart motor which would also unlatch
The bit that was latched

If Im off here please help me simplify this

Thanks
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