Startup and Shutdown

I am monitoring the amperage on a motor1. If motor1 exceeds current limit2, i kill the entire operation and it must be manually restarted. If it goes above current limit1, i kill motor2 and motor3. Motor 2&3 feed motor1 so by killing them, motor one has time to finish its task and in turn, drop its amperage back down to an acceptable level.

My only problem is that they want motor 2&3 to come back online if the amperage drops back down to an acceptable level. I have it set so that motor1 must be running and the amperage is below a set value for more than XX seconds, i can use the dn bit to re-enable the motors. I don't know why they would run motor1 without the other 2 on but i don't want those to start automatically unless it is after a failure. How would one do that? Does that make any sense? I'm not the greatest as explaining stuff. Please let me know if there is something faulty about what i wrote. I am still learning this.

One thing that helps in any analysis is to break down the final action into its constituent parts and handle them separately.

Your description kind of tossed everything together but in all cases there are really (at least) two things required for the motors to run:
1) Do you (the operator) want the motor to run
2) Is the motor allowed to run

Think of it kind of like an enable and a permissive. Code each function separately and combine the effects at the output driver. Ultimately this approach will allow you greater freedom in how the system acts and make it easier to modify if you need to.

Keith

that got me thinking.


i bet a could latch B3.X when the limit1 is exceeded and then make that condition for the motors to turn on. The dn bit from the restart would unlatch it.

does that make sense

My first thought is safety naturally, can anyone be harmed becaused the motors have stopped but may start on their own?

My second thought was why not have a slightly larger and possibly faster motor for #1. I do not know the application but it is a thought.

Looking at your snippet of code I wonder why you need the MOV's at all, they are unconditioned so why not just have the timers preset with that value?

The re-enable timer may need more conditioning i.e. motor 2&3 were ON but now off because of overcurrent. Search for WAS bit to help with this.

If they push to have it re-enable itself then I would at least add an alarm light to flash when motor 2&3 are temporarily off from overcurrent condition. HAVE TO TEACH THE OPERATORS ABOUT THE LIGHT THOUGH and make it very visible.

Do not overcomplicate it, think if, then, else. If I work then I must get out of bed else I will lose my job.

there is no danger to personel due to motors intermittently starting and stopping. The amperage overload is a fault of the operators when they force too much raw product into the process and then when it gets to the mixer (motor1) it bogs it down. We already have a 75horse motor on a mill rated for a 60 horse. Motors 2 and 3 consists of the rotary gate and freeze tunnel which feed the mixer.

Can you set an HMI to write directly to the .pre? I haven't done that before and have always had the hmi write to an integer and then move that to the .pre. They will be playing with the times and amperages so pretty much everything needs to have the ability to be changed via the hmi.

this is with the latch change

If using an HMI then using integer files and the MOV is appropriate, had to ask.

ok cool. does it look like the restart will work? Only come back on in auto if the stop was caused by an overload.....

Given that structure, how do you get motors 2 & 3 to turn on in the first place?


Keith

the entire opertation is started manually via the hmi. They start the motors one at a time. Thats why i have motor 1 running as a condition for the monitoring to be enabled. They always start motor1 last so i know the other motors will already be on

Then I would just use the .DN bits from the monitor timers directly as conditions to run the motors. Use the operator selected run condition from the HMI in series with the appropriate .DN bit and drive the output.

Also, some people don't like them, but don't be afriad of off-delay timers. When you are trying to put time delays on both sides of an action they can make the logic conceptually alot cleaner.

Keith