Measurement of Power Consumption

Just been given a new project for our test lab.

Basically I need to figure out the efficiency of our different conveyors.

Efficiency is the amout of material moved for the amount of power applied.

My question is what would be the most accurate way to measure power consumed. My thought is to measure current and voltage going into the drive while measuring the rate of discharge.

Any ideas?

We use the following and you can get a 4-20ma output.

http://www.loadcontrols.com/products/products.html

Just remember that the draw will spike when the load is applied not when it is discharged so if your load is variable there will be a lag between your two readings which will increase with the length of the conveyor. Your readings will also be an indicator of any mechanical problems as they will increase the power draw.

Ventax said:

Just remember that the draw will spike when the load is applied not when it is discharged so if your load is variable there will be a lag between your two readings which will increase with the length of the conveyor. Your readings will also be an indicator of any mechanical problems as they will increase the power draw.

Click to expand...

Yea I thought about the loading effect. I will be using 2 weighing platforms. One on the input side measuring how much we are putting in and one on the output side measuring how much we are discharging. "Seeing" the lag and flow rate are important as well.

I think the easy part is measuring the energy input ie power - simply done with a current and voltage measurement and use a data logger.
Should only take a $1,000 of equipment and time to install.

The hard part is going to be measuring how much material is moved.

This strikes me as $5 chasing a $0.05. If this is coming from the beancounters give them a practical lesson involving them getting away from their desk a shovel and wheelbarrow.

Dan Bentler

Clay B. said:

Yea I thought about the loading effect. I will be using 2 weighing platforms. One on the input side measuring how much we are putting in and one on the output side measuring how much we are discharging. "Seeing" the lag and flow rate are important as well.

Click to expand...

Unless your product evaporates, you can fifo your input readings for the duration of the trip and not bother with the discharge readings. that would give you the true product load (by summing the fifo register) without the second scale.

leitmotif said:

I think the easy part is measuring the energy input ie power - simply done with a current and voltage measurement and use a data logger.
Should only take a $1,000 of equipment and time to install.

The hard part is going to be measuring how much material is moved.

This strikes me as $5 chasing a $0.05. If this is coming from the beancounters give them a practical lesson involving them getting away from their desk a shovel and wheelbarrow.

Dan Bentler

Click to expand...

Using a data logger would be the easiest route. The issue is I want this data relative in time to my thruput. I also want to have this data in the same location IE...Right now I am looking at a Data Station from Red Lion.

I guess a better way to pose my question would be: Will I miss anything by just measuring the power into the drive. I do not believe I will but I have missed things before.

As for the reasoning behind it, We are an OEM so we want to use this data to show our customers. Plus this is data we really do not have at this time and sizing is more guess work than anything else.

Ventax said:

Unless your product evaporates, you can fifo your input readings for the duration of the trip and not bother with the discharge readings. that would give you the true product load (by summing the fifo register) without the second scale.

Click to expand...

True, I can measure either end (input or discharge) and get thruput once the conveyor is up to speed but the mechinical guys want the initial lag graphed so they can see the inertia. This is to aid in gearing and motor sizing.

Clay
Since this is machine testing and measurement I would be very interested in this project. The question of inertia I find most interesting because I do not really understand how to handle it mostly for lack of practice.

Seems to me you are going to have to know based on data logger readings pounds per minute both going on conveyer and going off and an average of current per minute. If you can get these measurements each and every second or faster then you can let computer boil down teh data for you - this part I am good at - but once I get the numbers out I am not sure what to do with them - in this case what type of motor or what size shaft and chain to handle inertia - again from lack of practice.

The other good thing about measuring product on and off is you can show a number for spillage.

I assume this conveyer leans more to tons per minute than pounds per hour. So you suddenly dump two ton of stuff which also causes the belt to stretch - how do you measure this - movement of belt tension weight? So when you measure this how do you plug this back into inertia calcs?

Dan Bentler

Better Description

I think from Dan's responce I need a better description.

The conveyors we make come in 4 flavors: Aero Mechanical, Flexible Screw, Rigid Screw and Drag. Each of these conveyors are considered "contained" or no material loss from one end to the other. Each conveyor has it's own unique charistics.

All of the conveyors are built for bulk material handling. Materials like salt, sugar, coffee beans...etc

The testing is for several different charistics. We basically want to create a data base that shows for a given product at an expected rate what conveyor would be the most efficent and what power it would consume.

The inertia part is because as you start to move powders you have a loading effect in that the powder starts to compress before it start to fluidize. We want to find this factor so that the motor that is sized is geared high enough or the horse power is high enough that we do not stall.

Another part is that on some conveyors you have to meter the amount of material to prevent ovewhelming the conveyor. We need to determine exactly when this can happen.

Because the variables are conveyor angle, size, type, speed, material flow charistics, and thruput demand, I need to be able to test each variable and see its effect.

Couldn't you just monitor the power output on the drive display, or map that drive parameter to a analog output from the drive?

we use a powermonitor from allen bradley, they have ethernet/ip interface, we have 62 of them.
The model we use is PM1000 there are other models but they have mor features and they´re more expensive.
We use a ML1100 to gather info from those monitors and we get data by shift, by day by month etc etc.

Brownhat said:

Couldn't you just monitor the power output on the drive display, or map that drive parameter to a analog output from the drive?

Click to expand...

I think that is what I would do, and then just hook up to a chart recorder.

allscott said:

I think that is what I would do, and then just hook up to a chart recorder.

Click to expand...

The problem with that is I need to see how power consumption relates to material thruput.

I have been doing some research on my own and I think I am going to use the Red Lion Module controller. They have a card that can take 2 weight inputs at the same time. I am also planning on using some current Meters to monitor power consumption via voltage/ current measurement. These will be connected via analog to the Red Lion. I want to reserve the serial comms to the drives (ModBus) for set up and speed control. In my test panel I am planning on using 10 Hp drives. We use 2 HP to 7.5 HP motors on our conveyors currently. I also found on Red Lion's site a RPM sensor that mounts to the C-Face of the motor so I can use it to measure RPM.

From what I am currently looking at I will trigger a reading of power and thruput every .5 seconds once the drive is too the test speed.