Working out running cost of 3 ph machine

[flyingsparks]

Customer has a large laser cutter, 3ph 100A supply and they want to work out fairly accurately what it's costing to run and for cutting different materials, thicknesses etc..

One option is to use 3 clip on energy monitors, one for each phase, but then they are not truly accurate due assuming a constant voltage and not taking power factor into account. I am not sure I will be able to find out the power factor of the machine to make these adjustments.

Any other ideas? How far out do you think the clip on monitor idea is going to be?

 

[plugwash]

How about just using an electricty meter.

http://www.universalmeterservices.c...t174-three-phase-meter-direct-wire-p-131.html (note: found with a quick google search, there may well be better suppliers).

 

[big-all]

can you not do a background level with nothing drawing more than say 200w[computers lighting ect] over several hours to give a back ground average

then when it comes time to run the machine through a program make sure the background is the same items running and remove the average from equation
or use a different circuit purely for this machine and read the supply meter through several cycles

 

[flameport]

How far out do you think the clip on monitor idea is going to be?

Far enough away to be totally useless.

 

[bernardgreen]

Clip ons will never be accurate as there is a gap in the magnetic core.

Thread the leads through current transformers and you will get currents in the secondaries that can be used to give accurate measurements of the current. Using a data logger to record the currents and voltage during a cutting program will, with some analyse provide detailed information about the power used by the various modes of cutting.

http://www.wessexpower.co.uk/manufacturers/grant/?gclid=CPWUhtfP9bsCFeTLtAod8XwA1Q is one source of the Squirel range of data loggers,

There are many others..... Pico have some PC based logging systems

 

[flyingsparks]

Clip ons will never be accurate as there is a gap in the magnetic core.

Thread the leads through current transformers and you will get currents in the secondaries that can be used to give accurate measurements of the current. Using a data logger to record the currents and voltage during a cutting program will, with some analyse provide detailed information about the power used by the various modes of cutting.

http://www.wessexpower.co.uk/manufacturers/grant/?gclid=CPWUhtfP9bsCFeTLtAod8XwA1Q is one source of the Squirel range of data loggers,

There are many others..... Pico have some PC based logging systems

Had a look at the squirrel loggers, quite expensive at around £1000. Does anyone hire such things do you know?

 

[ericmark]

I know when working on the building of T5 we hired data loggers for the cranes to show when they were running. These would do the job but not a clue on cost.

 

[bernardgreen]

Does anyone hire such things do you know?

I has been long time since I used them but I recall Grant at Cambridge either hired them out or told us where we could hire them from.

Look at Pico as an alternative though for most you need a PC or laptop to store the data

http://www.picotech.com/current-data-logger.html

http://www.picotech.com/data.html

 

[flyingsparks]

Thanks Bernard, the picolog cm3 only measures the 3 currents, no voltages are recorded. Surely to accurately work out the power used, one would also need to know the voltages at the same time?

 

[ChrisRogers]

I have a fluke 1735 power logger that's available for hire if required.

 

[bernardgreen]

Thanks Bernard, the picolog cm3 only measures the 3 currents, no voltages are recorded. Surely to accurately work out the power used, one would also need to know the voltages at the same time?

From memory there is a 4 channel voltage recorder. The currrents would be measured using current transformers each with a resistor to convert secondary current into a voltage. Whether it would be necessary to record each of the phase voltages or trust that they would all be roughly the same is open to debate.

Have you ( or the machine owner ) looked to see if the machine has its own power monitoring system that could be read and recorded in real time.

 

[flyingsparks]

I have a fluke 1735 power logger that's available for hire if required.

Accept my friend request so I can PM you please. Thanks