Chart Recorder for Motor Current?

[sii]

I have a 125 hp motor for which I would like to chart the motor current. I was thinking of using a current transducer to drive something like http://www.partlow.ca/arc4100.htm but I'm concerned what the chart will look like as this motor drives a large pulverizer and the current spikes all over the place regularly. Any better ideas?

edit: transducer not transformer

 

[petersonra]

I have a 125 hp motor for which I would like to chart the motor current. I was thinking of using a current transducer to drive something like http://www.partlow.ca/arc4100.htm but I'm concerned what the chart will look like as this motor drives a large pulverizer and the current spikes all over the place regularly. Any better ideas?

edit: transducer not transformer

If there are current spikes that is what the recorder will record. I don't see how you can get around that.

 

[sii]

If there are current spikes that is what the recorder will record. I don't see how you can get around that.

I get that. The chart I'd like to use (because we use the same one for another application) allows me to filter the input over 10-20 seconds so that should smooth it out a bit. I was just hoping someone had tried this elsewhere.

 

[iceworm]

I have a 125 hp motor for which I would like to chart the motor current. I was thinking of using a current transducer to drive something like http://www.partlow.ca/arc4100.htm but I'm concerned what the chart will look like as this motor drives a large pulverizer and the current spikes all over the place regularly. ...

It likely will look like a solid thick band around the chart. You will know the upper and lower bounds within the inertia of the pens. Unless a paper chart was all that was available, I'd pick a modern electronic.

The choice of a recorder is dependent on the required information. I've picked a slow (~100 samples/sec) electronic version of a paper recorder, such as an Omega RD5283 ($800). And I'm using a Dranetz PX5 for capturing sub-milisecond transients ($12k). I do not recommend Dranetz. And I am looking at an Elspec g4500 ($9K) for three phase transient monitoring.

Depends on what you are trying to find. However, paper, while workable for some applications, would be at the bottom on my list.

ice

 

[Besoeker]

I have a 125 hp motor for which I would like to chart the motor current. I was thinking of using a current transducer to drive something like http://www.partlow.ca/arc4100.htm but I'm concerned what the chart will look like as this motor drives a large pulverizer and the current spikes all over the place regularly. Any better ideas?

edit: transducer not transformer

Maybe you could explain what you want to determine from the recordings. That might elicit some more specific answers.

 

[Jraef]

Maybe you could explain what you want to determine from the recordings. That might elicit some more specific answers.

Agreed.

In addition, there are several data logger systems and even solid state overload relays available now that, if you have a PLC or something Network compatible, would be able to accomplish this for you. So describe the entire situation as well.

 

[ptonsparky]

We use PLCs with analog inputs, transducers and a better HMI with USB storage, on projects to track trends as a side benifit to control. The HMI will average x number of readings and save that value as well as plotting a trending line for you. Give it a network connection and it will send you the data when stuff hits the fan.

Probably cheaper to buy a real meter. Better, too. Lot easier to move around.

 

[GeorgeB]

I have a 125 hp motor for which I would like to chart the motor current. I was thinking of using a current transducer to drive something. I'm concerned what the chart will look like as this motor drives a large pulverizer and the current spikes all over the place regularly. Any better ideas?

I do it regularly on hydraulic power unit motors. My method is an older Flukd clamp-on 1000:1 transformer style into a load resistor (I use a 20 ohm, 10 ohm, and 2 each 5 ohm units in stacking banana plugs) to the input of a "converter" from 1 VAC to DC to a Dataq data acquisition unit ... much simpler than it sounds. Most AC to DC converters have about 200 msec response and show the load quite well. Parts cost is in the $700 range with parts bought new. Mine is a little fancier as I also monitor flows, pressures, and signal voltages. Oh, my converter is an ActionPak G468 http://www.eurotherm.com/products/signal-conditioning/action/ultra-slimpak/g468/. It's the most expensive item.

 

[sii]

The motor drives a pulverizer to regrind polyethylene scrap and is fed by hand. The off-shift operators claim that any number of problems prevent them from generating much output. Example: I was doing pm's on other machines Saturday morning within earshot of the machine. It makes a distinctive sound when grinding and in 4 hours I never heard it grind anything, it sat spinning (60 amps @ 480) for four hours with no operator to be found. We end up disassembling the damn thing twice a week only to find nothing wrong.

One of the production supervisors sees the same thing I do but has been told he has to document it to discipline employees. I was asked how we could go about doing that. I have some $ left over from another project so I thought this might work.

The Omega chartless recorder above looks promising, I'll have a look at that tomorrow. I don't need to be tremendously accurate, it looks like the Omega can be setup to do what I want. Plus I don't have to worry about the operator "forgetting" to change the chart.

Forgot to add: no Plc, just a Motortronics soft starter.

 

[Cow]

If you're trying to prove operators aren't running the machine why don't you just point a camera at the machine? I would think that would also have the side benefit of motivating the employees to do some work if they think they are being watched rather than your method of trying to catch them not working.

 

[sii]

If you're trying to prove operators aren't running the machine why don't you just point a camera at the machine? I would think that would also have the side benefit of motivating the employees to do some work if they think they are being watched rather than your method of trying to catch them not working.

I suggested that and was told no. I've given up arguing. Besides, our IT dept would have to be involved in that and that's not going to happen right now.

 

[ptonsparky]

A few years ago one of my help and I ran a hay mill for a couple hours to make sure things worked as planned. We doubled production. Granted our goal was to find the weak spot (s) in the process. We did.

 

[Jraef]

If not a camera, you could just put in a simpler current switch that has a threshold set to the unloaded current level and a Form C relay output, so unless that current level is exceeded, the relay output stays off, if exceeded, it changes. Then wire that to a 3 color tower stack light. Red means it's running (energized by a starter aux.), amber I'd wire to NC on the current switch, blue I'd wire to the NO contact. So when the machine is started, the red light is on, but if it is sitting idle, the amber is on, make it flashing, and if they are feeding it material, it stays steady blue.

http://www.nktechnologies.com/current-sensing-switch/asxp-current-switch.html

http://ab.rockwellautomation.com/Signaling-Devices/Control-Tower-Stack-Lights

If you wanted to get real fancy, take the same signals into a micro PLC and run the outputs to the stack lights, but also internally record the amount of time each day that the machine is on, and which status the current switch contacts are in. Or if you want, send that same status of machine running + low current to a resettable Elapsed Time Meter. That way the operator can tell that you can see whether he is doing it right or not because of the tower lights, then at the end of each shift you can get a record of the productive time vs idle time, without the cost of a chart recorder, plus having to stock and constantly refill the paper, pen ink, etc.