Basic 3 Phase Question

Discussion in 'General Electronics Chat' started by WBogen, Apr 30, 2015.

  1. WBogen

    Thread Starter New Member

    Apr 30, 2015
    2
    0
    I was given some two channel amp readings from a 3 phase 480 volt motor; see sample below. How do I translate this to power being consumed? Thanks.
    NO.RMS/TRCH1CH2TIME
    1RMS31.7A33.9A23/02/15 08:38:05
    2RMS41.7A27.8A23/02/15 08:58:05
    3RMS24.1A25.0A23/02/15 09:18:05
    4RMS27.9A34.4A23/02/15 09:38:05
    5RMS24.9A27.6A23/02/15 09:58:05
    6RMS33.3A26.9A23/02/15 10:18:05
     
  2. Reloadron

    Active Member

    Jan 15, 2015
    969
    235
    I suggest you read this as to calculating 3 phase power. You are not recording enough data. To simply state 480 volts is not enough, each phase should be recorded and measured. Next each phase current needs measured and recorded and finally the power factor needs know. What I see looks like someone recorded some data every 20 min between 08:38:05 and 10:18:05 which included two channels of current. The data isn't even separated making it hard to interpret. If there was enough data to get the actual power then the numbers could get you to KWH but I don't see enough data.

    Ron
     
  3. WBogen

    Thread Starter New Member

    Apr 30, 2015
    2
    0
    Sorry, I should have separated the data better to make it more understandable:
    NO. RMS/TR CH1 CH2 TIME
    1 RMS 31.7A 33.9A 23/02/15 08:38:05
    2 RMS 41.7A 27.8A 23/02/15 08:58:05
    3 RMS 24.1A 25.0A 23/02/15 09:18:05
    4 RMS 27.9A 34.4A 23/02/15 09:38:05
    5 RMS 24.9A 27.6A 23/02/15 09:58:05
    6 RMS 33.3A 26.9A 23/02/15 10:18:05
     
  4. Reloadron

    Active Member

    Jan 15, 2015
    969
    235
    I was able to read the data, the problem I see is not enough data. Looks like the current of two of three phases is being measured. Take for example a three phase delta supply driving a motor. To calculate the power used by the motor with any degree of accuracy:

    You can't just assume 480 Volts, each phase voltage needs measured then averaged, the same for each phase current. Those numbers are multiplied by the power factor and then 1.732 the square root of three (Three Phase). So what I am saying is there is not enough data to answer the question. You can't convert the data you have to the power being used by the 3 phase motor.

    Ron
     
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