Electrical Consumption of Machine

In summary: You'd also need the motor's nameplate kW, V, and A. And a calculator. And you'd need to calculate the apparent power of the motor from the nameplate data. You'd also need to measure the current on all three phases, and the voltage on all three phases, of the motor. Then you'd calculate the power factor. It would be a rough estimate, but it would get you in the ballpark.
  • #1
Berk
9
0
I need to know how much electricity a machine uses in kW please.

On the machine information plate it states: 460 volts, 60 Hz, 161 amps, and it is a 3 phase.

I took the readings for the volts and amps:
Phase 1- 271 volts & 37.68 Amps
Phase 2- 271 volts & 37.62 Amps
Phase 3- 273 volts & 38 Amps

I cannot figure out the Power Factor to apply to the formula I am using:
kW= (Volts x Amps x Power Factor x Sqrt 3) / 1,000

I know Power Factor = Real Power/ Apparent Power, however I cannot figure out the real power. I believe the apparent power is (460 x 161 x Sqrt 3) / 1,000 = 128.27 kVA?

Could I just average the voltage readings and then average the amperage readings for the 3 phases and then do (Avg volt x Avg amp x Sqrt 3) / 1,000 to get the true/real power without using the Power Factor?

Are my assumptions correct? Can someone please help me calculate the electrical consumption please! Thank you
 
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  • #2
Welcome to PF!

You're pretty close: you don't have a measurement of power factor, so the best you can do is estimate. If you describe the application, we can help with that. If this is a 1/4 loaded motor, I'd use 60%. Otherwise, your calculation is fine.
 
  • #3
The machine in question is an industrial parts washer. How would I find out if it is a 1/4 loaded motor? When you say my calculation is fine, are you referring to using the nameplate amps x volts or the avg amps x avg volts readings that I got with the device?
 
  • #4
Berk said:
Can someone please help me calculate the electrical consumption please! Thank you
I'm afraid not. You need to know or measure power factor.
 
  • #5
How would I measure the power factor with the given information? Or do I need additional information? I have the voltage and amps for each phase and the kVA.
 
  • #6
The readings you took are the actual load and they were about 1/4 of the nameplate. So that's the second calculation.

Also, when you say a parts washer, that makes the load pumps and a conveyor? Or is there electric heat as wel? And do any of the motors have VFDs?
 
  • #7
Berk said:
How would I measure the power factor with the given information? Or do I need additional information? I have the voltage and amps for each phase and the kVA.
Measuring power factor is done with a power meter.
 
  • #8
Berk said:
How would I measure the power factor with the given information? Or do I need additional information? I have the voltage and amps for each phase and the kVA.
You can measure/determine it with cos(φ)-meter or clamp on-power meter or any kind of wattmeter . To calculate/estimate it you should now what motor exactly you have. So, nothing about cos φn on the nameplate?
 
  • #9
zoki85 said:
I'm afraid not. You need to know or measure power factor.
For most purposes you can estimate it close enough for a useful answer, though it does depend on the required precision.
 
  • #10
I do not know if the motor has VFDs, and the parts washer is basically a big conveyor belt system. I believe there is electric heat as well, not sure though.I cannot attach the manual because it is larger than 3 MB. I have 2 tools at my disposal, a Fluke 115 True RMS Multimeter & a Fluke 325 True RMS Clamp Meter. If you could please guide me through the steps needed to calculate the most accurate kW (true power) with the resources at my disposal, I will be eternally grateful. Thank you!
 
  • #11
russ_watters said:
For most purposes you can estimate it close enough for a useful answer, though it does depend on the required precision.
cos φ estimations get more shaky more you're off the nominal power of machines.
 
  • #12
Berk said:
I do not know if the motor has VFDs, and the parts washer is basically a big conveyor belt system. I believe there is electric heat as well, not sure though.I cannot attach the manual because it is larger than 3 MB. I have 2 tools at my disposal, a Fluke 115 True RMS Multimeter & a Fluke 325 True RMS Clamp Meter. If you could please guide me through the steps needed to calculate the most accurate kW (true power) with the resources at my disposal, I will be eternally grateful. Thank you!
With your equipment you can't measure or calculate power factor. You need a power meter and unfortunately, they aren't cheap:
http://www.fluke.com/fluke/m3en/solutions/pq/

To estimate the power factor, you need to know how much of the load is resistive (from the heaters) and how much is inductive (from the motors). You'll need amperage readings for each motor feed and the nameplate amperage of each motor.

If the pumps or motors change speed, they are probably on VFDs, but if they were, you'd probably also get true power readings from the VFDs, so I'm guessing they are not.
 
  • #13
zoki85 said:
cos φ estimations get more shaky more you're off the nominal power of machines.
Yes, but if he has a name brand motor with performance curves, he can get very close. If not...
[edit] oops...looks like it was worse than I remembered. Below 50% load, it starts getting pretty bad:

motor%20powerf_doe-med.jpg
 
  • #14
What is the cheapest Wattmeter I can buy that can be used on a 460 volt, 161 amp machine?
 
  • #16
Baldor JMM3713T 15HP 3450RPM 3PH 60HZ 215JM 3744M TEFC

https://www.mrosupply.com/motors/ac-motors/pump-motors/24080_jmm3713t_baldor-electric-motors/?gclid=CLyZpJuyrcICFVJhfgodTiYApw

This is the motor on the parts washer. What is the next step to figure out the kW (True Power)?
 
  • #17
Berk said:
Baldor JMM3713T 15HP 3450RPM 3PH 60HZ 215JM 3744M TEFC

https://www.mrosupply.com/motors/ac-motors/pump-motors/24080_jmm3713t_baldor-electric-motors/?gclid=CLyZpJuyrcICFVJhfgodTiYApw

This is the motor on the parts washer. What is the next step to figure out the kW (True Power)?
Performance graph (p6).
Line current drawn at 460 V (266V phase to neutral) → Power factor (cos φ).
This should give you a good estimate of a true electrical power of the motor since Pel= 460⋅I⋅√3 ⋅cos φ
 
  • #18
Berk said:
What is the cheapest Wattmeter I can buy that can be used on a 460 volt, 161 amp machine?
If you were able to switch off all but low-power machinery (and restrict the lighting) in the shop, and just run that motor alone at the intended loading, you might⋇ be able to see how much your workshop's power meter advances in 15 minutes of running, then x4 for the figure of actual power drawn. ⋇Depends on the meter―some of these electronic ones I think only the utility company can read.

It might be more practiceable to switch off everything else on just one of the phases, at least, to devote one phase's watthour meter to this motor exclusively, for 15 mins to do the test? (Monitor the 3 currents to confirm loading is balanced.)
 
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  • #19
Berk said:
Baldor JMM3713T 15HP 3450RPM 3PH 60HZ 215JM 3744M TEFC

https://www.mrosupply.com/motors/ac-motors/pump-motors/24080_jmm3713t_baldor-electric-motors/?gclid=CLyZpJuyrcICFVJhfgodTiYApw

This is the motor on the parts washer. What is the next step to figure out the kW (True Power)?
Is that the only motor in the washer? Doesn't it have a water pump and a conveyor?

If it is the only motor, that motor is so small compared to your nameplate electrical capacity that you could probably ignore it and assume all of your electrical usage is the electric heat at a 100% power factor. I'd probably still measure its amperage directly though.
 
  • #20
Well there are 2 of those motors actually as well as a few heating elements (pads). I'm figuring that the calculations are going to be fairly complex, so I am trying to find someone who will lend me an industrial wattmeter.
 
  • #21
Depending on where you live, you may be able to "rent" a recorder from a local electrician. I work for an electrical contractor, and we have come in and set up a 3 phase recorder for 2 to 14 days and then downloaded the file and sent it to the customer. If you find someone locally that has one you may have to pay them for its use (do you have an electrician who takes care or your place?). With the file you can look at voltage per phase to neutral (min, max, avg, and inst), current per phase (min, max, avg and inst), power factor, and voltage phase to phase.
BTW the files can become very large. Once we left a recorder on a service for 14 days, and took a reading every second, and the file would have been >700 pages if printed out. Thank goodness for computers to analyze the info.

Bottom line - see if you can beg, borrow or rent one from a larger electrician locally.
 
Last edited:
  • #22
wirenut said:
Depending on where you live, you may be able to "rent" a recorder from a local electrician. I work for an electrical contractor, and we have come in and set up a 3 phase recorder for 2 to 14 days and then downloaded the file and sent it to the customer. If you find someone locally that has one you may have to pay them for its use (do you have an electrician who takes care or your place?). With the file you can look at voltage per phase to neutral (min, max, avg, and inst), current per phase (min, max, avg and inst), power factor, and voltage phase to phase.
BTW the files can become very large. Once we left a recorder on a service for 14 days, and took a reading every second, and the file would have been >700 pages if printed out. Thank goodness for computers to analyze the info.

Bottom line - see if you can beg, borrow or rent one from a larger electrician locally.
 
  • #23
Haha thanks for the information
 

1. What is the definition of electrical consumption of a machine?

The electrical consumption of a machine refers to the amount of electricity that a machine uses while it is in operation. This can vary depending on the type of machine, its size, and its efficiency.

2. How is the electrical consumption of a machine measured?

The electrical consumption of a machine is typically measured in kilowatt-hours (kWh). This is the amount of energy used by the machine over a period of time, usually one hour. It can be calculated by multiplying the power of the machine (in kilowatts) by the time it is in use (in hours).

3. What factors affect the electrical consumption of a machine?

The electrical consumption of a machine can be affected by various factors such as its size, efficiency, age, and type of energy source. Additionally, how often the machine is used and the length of time it is in operation can also impact its electrical consumption.

4. How can the electrical consumption of a machine be reduced?

The electrical consumption of a machine can be reduced by using energy-efficient models, properly maintaining the machine, and turning off or unplugging the machine when it is not in use. Additionally, using alternative energy sources such as solar or wind power can also help reduce electrical consumption.

5. Why is it important to monitor the electrical consumption of machines?

Monitoring the electrical consumption of machines is important for several reasons. It can help identify energy-efficient machines, reduce energy costs, and track the environmental impact of using certain machines. It can also help identify any potential issues with the machine's operation or maintenance that may be causing higher electrical consumption.

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