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How can I measure the energy consumption in CNC machines without using Energy (Power)

aqib111

Plastic
Joined
Jan 26, 2018
I can't afford to buy an Energy Analyzer. I am planning to record the energy consumed by Milling operation when different parameters are used to machine and find out the variation. There is no Energy Analyzer available here. Any other way to measure the power consumed and verify that?
 
A domestic energy display works for a small machine (13amps or less in uk) about £14 I'm told, 3 phase is harder, unless your spindle is on one phase, but there is usually an ammeter on the pendant, most cnc machines have a graph these days (fanuc robodrill had a power monitor for tool wear etc, don't know if that was a standard thing)
Clamp meter is the easiest, can wire it to a data logger for analysis on a spreadsheet
Mark
 
Unless your machine is fully power factor corrected, an amp meter is not going to show you power levels.

Power = V x A x Pf

Yes, measuring just amps will give you an indication, but unless you can measure Pf simultaneous with Amps you won't really know what's going on.

Can your machine show you % of spindle power used? That will give you a relative indication between settings (assuming tooling is the same wear level). If not available as a front panel option you might be able to see this as a display parameter on the spindle VFD.

You can also look at amps on most vfd's. VFD access assumes your manf hasn't locked you out of the access. I look at mine as an indication of tool wear.
 
For most ac loads simply measuring amps and volts then multiplying won't work.

Power meters multiply them in real time many times per second and then calculate the value.

Question is do you really need to know power? If you are simply trying to determine the effects of various operations amperes will give you at least some indication. It's not as precise but if you have no way to measure power it might have to do.
 
I do not have any specific device in mind, but I searched for "power meter" and got over 8,000,000 hits. Just on the first page the prices ranged from under $20 for a hand held device. I am sure you will need something bigger, but there are literally thousands of them out there; many, dare I say MOST of them are made in China.
 
Whilst its true amps times volts won't work for ac because of phase angle, it probally will do just fine for your needs, for a given motor - drive combo the phase angle will remain much the same at a given speed, hence it should give you some reasonably solid idea.
 
The OP has:
1. Listed themselves as a "student"
2. Revealed that they have "no money"
3. Have not been back since to offer up
more information.
 
Whilst its true amps times volts won't work for ac because of phase angle, it probally will do just fine for your needs, for a given motor - drive combo the phase angle will remain much the same at a given speed, hence it should give you some reasonably solid idea.

Phase angle (Pf) will remain the same for a given power not necessarily speed. If the aim is to mess with speed and feed etc, power is a variable which is what he is trying to measure.
 








 
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