# Emergency amp load setpoint to 110v control valve



## micromind (Aug 11, 2007)

What feeds the crusher? 

Typically, the feed belt in on a VFD and if the VFD has built-in PID, it can be programmed to sort of maintain a certain motor amp range using a 4-20 CT on the crusher motor. 

This is not exact by any means, it'll vary quite a bit depending on what size of rocks is being fed. 

If the VFD doesn't have PID capability, the crusher amps will be all over the place. 

Usually, the operator will keep an eye on the crusher amps and adjust the feed belt accordingly. 

Further, what will happen if large rocks come out the bottom of the crusher? If there's a screen and whatever dances across the top of it goes back to the crusher, you'll have a pretty good-sized surge whenever the valve opens. The amps will go up, the valve will open again.........

I'm not sure but you might have better luck varying the feed rate.


----------



## Go_snow (Jan 15, 2014)

The cone is fed from a screen deck. Unfortunately we have no hopper to feed the cone (the right way to do it and then control cone feed by conveyor speed as you spoke of). If cone drops, oversized recirculates to another screen and then circulates back through the system. So it doesn’t cause any pile contamination etc.


----------



## gpop (May 14, 2018)

Look. At a shock relay with remote ct. It needs to be self reseting or have the remote reset function.
Instead of wiring it to the instructions just use the dry contacts to activate a timer relay for the dump.

May even be able to build your own with a 5:500 ct and a cheap ice digital adjustable overload block ( self resetting )


----------



## oliquir (Jan 13, 2011)

For a project like that use a small plc (or a smart relay with 0-10v input) that will let you do exactly what you want easily
just need the plc , one current transducer and one relay


----------



## Go_snow (Jan 15, 2014)

Thanks for all the replies! Would anyone be able to point me in the direction of some of the products suggested? I did some more research early this morning, but with a knowledge level of about 0 on all of this, I don't know exactly what I'm looking for. I would love to learn how to program PLC etc, but with running the concrete and aggregate companies, and two little children, I don't know if I have the time :vs_mad:


----------



## splatz (May 23, 2015)

Go_snow said:


> Thanks for all the replies! Would anyone be able to point me in the direction of some of the products suggested? I did some more research early this morning, but with a knowledge level of about 0 on all of this, I don't know exactly what I'm looking for. I would love to learn how to program PLC etc, but with running the concrete and aggregate companies, and two little children, I don't know if I have the time :vs_mad:


Can't you get someone in just to put it together for / with you? 

Be careful with the CT, you can't leave those in place and open!


----------



## splatz (May 23, 2015)

gpop said:


> Look. At a shock relay with remote ct. It needs to be self reseting or have the remote reset function.
> Instead of wiring it to the instructions just use the dry contacts to activate a timer relay for the dump.
> 
> May even be able to build your own with a 5:500 ct and a cheap ice digital adjustable overload block ( self resetting )


This seems like the simplest solution to me. I had not seen these before but I googled. This is the first one I found 

https://www.ustsubaki.com/pdf/L14020-Tsubaki-shorter-ShockRelay_small.pdf 

These have a settable "Shock Time" which I believe would make the timing relay unnecessary. 

If this device does it in a single off the shelf component, that's usually hard to beat.


----------



## Go_snow (Jan 15, 2014)

I'd have someone else do it, but we live in a very small town and I doubt there is someone here with that skill set. I just was looking at the Tsubaki Pdf prior to you posting that. Looks like you would wire in the shock relay in to the motor and then a 120v would go to the valve rather than the motor control unit?


----------



## gpop (May 14, 2018)

No reason you couldnt sub a bench built solution from one of the programmers on here then do the install.
E.G. programmed relay with remote ct and pot adjustable timing on a set of dry contacts. 

I dont buy parts so i have no idea what things cost.


----------



## gpop (May 14, 2018)

splatz said:


> This seems like the simplest solution to me. I had not seen these before but I googled. This is the first one I found
> 
> https://www.ustsubaki.com/pdf/L14020-Tsubaki-shorter-ShockRelay_small.pdf
> 
> ...


Shock time is the time it takes to react to a violent shock. Overload time is the time it takes to react to a slow rise in the amps.

On a phone so no idea what the parameters are for self resetting.


----------



## Go_snow (Jan 15, 2014)

Here is another question or route I could potentially take. The cone is controlled hydraulically by a 2 hp 3 phase motor that runs a hydraulic pump. Would it be better to run the pump motor with a vfd with an input 4-20 input from a current sensor monitoring the cone current?

https://www.automationdirect.com/ad...ltage_Sensors_(AC_-a-_DC)/Current_Transducers

Then you could use the parameters of the vfd to control amp on motor. Say you tell vfd to keep amp between 100-200 amps?


----------



## splatz (May 23, 2015)

Go_snow said:


> Here is another question or route I could potentially take. The cone is controlled hydraulically by a 2 hp 3 phase motor that runs a hydraulic pump. Would it be better to run the pump motor with a vfd with an input 4-20 input from a current sensor monitoring the cone current?


I wouldn't know whether that would be doable, or whether it would be better? 

If I follow you, that's along the lines of what @micromind suggested using a PID loop to control the feed. You'd be monitoring the current on the crusher motor to fine tune the action of the cone's hydraulic pump motor with a VFD, rather than just turning the pump off.

For me, tuning the VFD would be more challenging than the shock relay, depends how adventurous I am feeling.


----------



## gpop (May 14, 2018)

The time between cause and affect has a huge factor on a pid loop. Im not sure a vfd on a hydraulic pump would work as intended.


----------



## Go_snow (Jan 15, 2014)

Thanks for the response Splatz. I guess I was leaning towards something I have done before (abb 550 vfd to control level of tank). That being said, I will spend some more time researching this shock relay. Would you then use a ice cube relay to control the valve? Ice cube relay would get an input from the shock relay, open for specified time, then reset? I could also use a timer as well (which I have used in the past on on concrete plants).


----------



## splatz (May 23, 2015)

Go_snow said:


> Thanks for the response Splatz. I guess I was leaning towards something I have done before (abb 550 vfd to control level of tank). That being said, I will spend some more time researching this shock relay. Would you then use a ice cube relay to control the valve? Ice cube relay would get an input from the shock relay, open for specified time, then reset? I could also use a timer as well (which I have used in the past on on concrete plants).


I just skimmed the shock relay in the link I posted, the Japanese sounding name. That one looks to me like you set the shock current, which is the amp threshhold, start time, which is to accomodate startup inrush, and shock time, which is how long you must be over threshhold before it trips. The trip would be controlling the hydraulic pump motor. The operator has to reset it after it trips. Pretty simple but nothing fancy. Like it says in the PDF, it's like an electronic shear pin, but rather than stopping the motor that's over normal current, you're stopping the pump motor.


----------



## Go_snow (Jan 15, 2014)

So essentially when it hits the peak amp setting it sends a signal of some sort. What happens if that signal was sent to an electronic timer which then went to an electronic ball valve that opened to release hydraulic pressure and drop cone. The pump only runs when you are changing the height of the crusher. So a valve that dumped back to the tank would lower crusher. Then the operator would notice an increase in size of rock and need to reset the height, but the plant would continue to run.


----------



## splatz (May 23, 2015)

Go_snow said:


> So essentially when it hits the peak amp setting it sends a signal of some sort. What happens if that signal was sent to an electronic timer which then went to an electronic ball valve that opened to release hydraulic pressure and drop cone. The pump only runs when you are changing the height of the crusher. So a valve that dumped back to the tank would lower crusher. Then the operator would notice an increase in size of rock and need to reset the height, but the plant would continue to run.


The shock relay is a relay; it's a switch that operates on the presence of the shock condition, which is current over the (programmed) peak level for longer than the (programmed) shock time. Before that condition occurs, switch connects common to the NC contact; after it occurs, the switch connects common to the NO contact, and it stays that way until the operator hits the reset button. 

How you use those contacts to turn the valve on / off depends on the valve wiring, the operating voltage and current of the actuator, and the rating of the contacts on the shock relay. If the contacts can handle it, you could just have the NO contacts open the valve, nice and easy.


----------



## JRaef (Mar 23, 2009)

I'd bet a dollar to a donut that this functionality is already built into your VFD...


Post a make and model.


----------



## gpop (May 14, 2018)

JRaef said:


> I'd bet a dollar to a donut that this functionality is already built into your VFD...
> 
> 
> Post a make and model.


My understanding is the crusher main motor is a 200hp that has a overload relay.


----------



## Go_snow (Jan 15, 2014)

Correct, crusher is controlled by a soft start and an overload relay. The 2 hp 3 phase hydraulic pump is controlled by a reversing switch that controls up/down of the cone crusher. If I were to do it like the new crushers, the 2 hp pump motor would be controlled by a vfd that would automatically control the amperage by raising or lowering the cone. Therefor if you had a rock surge, the amps would increase and the vfd would automatically lower the cone reducing amperage. My concerned would be how to control up and down with a vfd if we did go that route. Any thoughts on that as well?


----------



## gpop (May 14, 2018)

Ive never worked on a concrete crusher but it sounds alot like a press we use.

On most of the hydraulic systems i have worked on the hydraulic motor is never reversed. directional Valves are used to control the up and down. 

If you are adjusting a gap to control the load on the main motor then the best feedback would be to measure the gap with a sensor. This would allow a pid loop controlled by a plc to see that it has done something as a reaction to high load which would allow for a very slow pid loop. Solenoid controlled valves would be used to control the distance via the plc. 

If your crusher uses active hydraulic pressure to control the load then a vfd might work.


----------



## splatz (May 23, 2015)

Question based on very limited experience with PID loops or with rock crushers. I would assume the rock crusher is pretty erratic, the load going all over the place, and the PID loop is pretty fussy, it needs fairly consistent, predictable response to the control to get its act together. For that reason I thought this might be hard to get working. Is the rock crusher less erratic than I think, or are the PID loops smarter than I think?


----------



## JRaef (Mar 23, 2009)

Go_snow said:


> Correct, crusher is controlled by a soft start and an overload relay. The 2 hp 3 phase hydraulic pump is controlled by a reversing switch that controls up/down of the cone crusher. If I were to do it like the new crushers, the 2 hp pump motor would be controlled by a vfd that would automatically control the amperage by raising or lowering the cone. Therefor if you had a rock surge, the amps would increase and the vfd would automatically lower the cone reducing amperage. My concerned would be how to control up and down with a vfd if we did go that route. Any thoughts on that as well?


Sorry, I was confused by this...


> This site has helped me greatly in the past setting up a VFD with level sensor for our aggregate wash plant.


I get it now.


OK then, I'll bet a dollar to a donut that, unless its some sort of antique scrap unit they got from an auction somewhere, your SOFT STARTER has this functionality built-in... Again, post some info on it.


----------



## paulengr (Oct 8, 2017)

Go_snow said:


> Clearly my electrical lingo is off, but I'm hoping I can explain what I'm dealing with. This site has helped me greatly in the past setting up a VFD with level sensor for our aggregate wash plant.


I've dealt with these tons of times.



> We have a 200 hp 3 phase 480 volt motor running a rock cone crusher. The crusher opening is controlled hydraulically. Therefor if you were to have a hydraulic line break, the crusher would lower and no crushing work would be done (amps would only go to what it requires to move the crusher). As we continue to mine the side of a mountain, we occasionally get into large areas with greater rock than sand. This causes our amp loads to increase, and if not monitored can cause amps to go over 250 etc. Ultimately, the overload relay kicks in and shuts the cone down and causes a massive mess.
> 
> What I'm hoping to accomplish is as follows.
> 
> ...


Two things here. First off to answer your question directly, you can get a current relay that does exactly what you want from Carlos Gavazzi. They are fairly inexpensive.

BUT, I'm also a process engineer so let's discuss the bigger picture and why virtually all the solutions that were mentioned won't work right. You have a closed loop system between the screen and the crusher. You have a feeder for the overall system most likely but remember that the flow rate is a combination of both the incoming feed AND the circulating load which might be several times more than the feeder flow rate. Most attempts to control this use a PID loop to control the feed but operators will just watch the top of the crusher and can often vastly improve on the production rates manually. But if you try to use a PID loop feeder when the system does choke from either the bond work index (crushability) or the percentage of oversize, the circulating load which isn't accounted for kills it. The best solution is a sliding mode controller. The way this works is that we need some kind of sensor such as a level sensor aimed in the top of the crusher to measure when it gets "full". You can use an analog signal but level sensing and control in rock crushers is usually futile Simple "whisker" switches on say a spring loaded plate where the rock pushes the plate down is a lot more reliable. Now to get into the PLC control for this...we need to linearly increase the feed rate but exponentially back off because we not only have to slow down a bit but we also have to get rid of the overload as quickly as possible so "over reacting" in this case is good, but first we want to test the waters by only backing off a bit and getting more and more aggressive if it's a real overload situation. So every few seconds we look at the sensor. If it's not full, increase the feed rate by a fixed amount...say 5%. Keep increasing every time by this same amount. BUT if it's full, decrease by twice the amount so we decrease by 10%. The next cycle we double again so we decrease the flow rate by 20%. Keep doubling each time until we get to "not full", then begin incrementally increasing the flow rate again. When it gets close to the right feed rate it will just sit there increasing and decreasing back and forth keeping the feed rate fairly steady but when the crusher loop gets overloaded, it backs off as fast as possible until it gets control back again...the way that a human deals with the same situation. The timer isn't terribly important but the location of the sensor is somewhat important because really we want to start backing off BEFORE the crusher starts overflowing off the head box or backing up into the conveyor. So it takes quick and decisive action. It's nonlinear...something that PID loops do NOT do well, and the effect (circulating load) is exponential so we've got to address it the same way.

This is by the way the same original control algorithm used for internet traffic and still is a major part of the flow control system today, the TCP "binary exponential backoff" algorithm which had to deal with the same problem....when we exceeded the capacity of the "pipe" the only way to respond was for everyone to back off quickly (exponentially) until packets stopped getting lost.

You can still use PID control if you want. Typical vibratory pan style feeders are anything but "linear" compared to conveyors and screws. So if you're dealing with a vibrating pan style feeder, putting a scale behind it with a PID controller is the best way I know of to get more consistent flow rate into the system, and will make the above main control loop work a lot better if you have a pan feeder. If you have a conveyor feeder until a silo/rock box then you really don't need this which is good because scale maintenance can be a bear even though the office always wants to know how much rock they ran.

The "shock relays" are for something entirely different. You have such a huge gear ratio that when the crusher gets overloaded, the standard motor overload relay doesn't detect that there's a problem because the bump in current isn't large enough to detect. A "shock relay" reacts to the rate that the current "jumps" so that when say a big rock or in cone crushers typically it eats a piece of steel or a bunch of clay and mud that gums it up, the shock relay reacts to the spike in the current.


----------



## Go_snow (Jan 15, 2014)

The shear knowledge of the people on this site is somewhat unreal to me. Thank you all for taking the time out of your day for answering my questions.

Paulengr, thank you for the response. We are a little different than most when it comes to crushing. We crush at 200 tph starting at a grizzly feeder, into a jaw crusher, into a screen, oversized goes to cone crusher, to screen, oversized returns to initial screen. Most operations of this size would have someone that monitors the plant and amp loads constantly. As we are a small family run business, my father runs the loader, while I monitor the plant. This means me walking around keeping conveyors clean, monitoring amp loads, mixing floculent, moving material with another loader etc. If I was sitting in the van watching amp loads, I would adjust feed rates or cone height as I watched amp loads. 

Unfortunately, this isn't something I can constantly be doing. So we have to set the feeder at a rate that makes the jaw and cone happy, and then make sure the loader operator doesn't find an excessively large load of rock. If he does, amps have the potential to sky rocket on the cone and shut down. When the cone shuts down, we have put excess wear on the belts, cone, motor, etc. 

I can see where PID loops wander like crazy, and in a crusher setting, could cause some very interesting re run (too big, too small). We also are in a situation where we are crushing from 3" down to 3/4" minus at sometimes 80+ ton per hour. Ideally our cone would be able to be choke fed (full) and a level sensor would be used, but the cone doesn't have the power to be choke fed at that reduction rate. Therefor a surge in rock creates a choke situation that causes the amps to quickly increase up to 400+. Ideally, you would have a 300-400 hp cone (but that would cost about 1/4 million dollars to get that). 

So, we make due with what we have. And being the manager of the company, I want jobs of my employees to essentially be as easy as possible. This means that if the loader operator accidentally catches a rocky load, we have a way to avoid a shutdown (or possibly worse, a cone failure due to extreme load). 

As we are again a small company, we try to minimize costs as best we can. So, I'm looking for an extremely cost effective way to do this (for the vfd with level control, I purchased an abb 550 40 hp from japan for 600 dollars and it has worked wonderfully). Level sensor came from automationdirect.com. Do you suggest getting ahold of Carlos Gavazzi? Or would you suggest an extremely cheap vfd that would strictly be used to control a 110v valve? Meaning power vfd, use a 4-20ma current sensor, and then use one of the terminals on the vfd to send a signal to the valve (setting a max amp etc)?

Thanks for all the help guys. One of these days, we will install a hopper before the cone with a vfd on the conveyor to the cone, but until then I will try to find an alternative.


----------



## paulengr (Oct 8, 2017)

Go_snow said:


> The shear knowledge of the people on this site is somewhat unreal to me. Thank you all for taking the time out of your day for answering my questions.
> 
> 
> 
> ...



If you’re in the Carolinas or Virginia I’d be the guy to put it in. We have a few quarry customers. Size doesn’t matter. In fact the big mines don’t use us except motor rebuilds.

Carlos Gavazzi is a company, not a person. Google it. They make nice current/voltage monitors that are cheap with relay outputs or 4-20. 

So if it’s just a hydraulic control valve (on/off) to drop the cone, use it directly. Worst case you might need a CT to convert the current to a working range (say 500:5) and/or maybe a 10 A ice cube relay if Gavazzis output contacts are too small. If you’re aiming for analog then drive the valve positioned right off the relay 4-20. I don’t know what your valve looks like. Positioners by the way can be expensive so if on/off works it’s a lot simpler and cheaper. Best “low” cost positioners I’ve used on the past is Honeywell. Beck is bulletproof but they charge bulletproof prices. Electro Sensors makes some nice grain industry options too. I’ve been keen on the ball screw stuff but that stuff flat out cannot take shock loads of any kind without getting flat spots in the balls...hint, hint not crusher duty. I like the concept all electric but not the reliability.



Sent from my iPhone using Tapatalk


----------

