Motor start timer after losing power

Ones_Zeros

Member
Join Date
Feb 2014
Location
at work
Posts
367
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:
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
 
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.
 
Last edited:
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.
 
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.
 
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.
 
Since I’m 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 I’m off here please help me simplify this

Thanks
 
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....


Necro-thread alert


What happens if, while both motors are off, the remote start is pressed on the 2nd motor, then 15s later the remote start is pressed on the 1st motor?
 
Another way is to set a "Motor Starting" coil when the first motor comes on but its starting timer hasn't timed out. A contact from this coil can inhibit the second motor starting.
 

Similar Topics

Does anyone know the best way to add a horn to a start button that stays on for 10 sec then shuts off and the motor starts.
Replies
15
Views
7,076
Does anyone know the bet way to add a horn to a start button that stays on for 10 sec then shuts off and the motor starts.
Replies
1
Views
3,193
Hi All, I have been asked to commission two new Powerflex 525 vfds on site which I've never done before and I've ran into a problem which I'm...
Replies
3
Views
1,337
Good Morning , We have a 100 HP , 480 V (Full Load Amps 124 ) Hammer Mill motor that has a Wye/Delta starting procedure. I would like to put...
Replies
16
Views
4,172
I have P036 configured as 2 wire SRC Control with an exteranl supply. I choose the direction with a 3 point rotary switch. The problem is when it...
Replies
1
Views
1,130
Back
Top Bottom