×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

actual work 380V vs 460V

actual work 380V vs 460V

actual work 380V vs 460V

(OP)
If I have a motor running a piece of equipment in the US on 460V 60HZ and it is drawing 100amps, how does that compare to one in Asia running on 380V 50HZ drawing 100 amps?

Are they both doing the same amount of work?  What is the formula to use to adjust them the amps so they are both doing the same amount of work?

Thanks

RE: actual work 380V vs 460V


In 380V 3ø circuits, each kVA of capacity corresponds to a per-phase current 1.52 amperes.  In 460V 3ø circuits, the ratio is 1.26 amperes/kVA, representing some conductor savings per unit power, but at the expense of heavier insulation.  

Frequency has no direct effect on electrical-power calculations.  The same ratios hold for 50- or 60-Hertz systems.
  

RE: actual work 380V vs 460V

Comment on mark754 (Electrical) Apr 5, 2004 marked ///\\\
If I have a motor running a piece of equipment in the US on 460V 60HZ and it is drawing 100amps, how does that compare to one in Asia running on 380V 50HZ drawing 100 amps?
///
1. 460V 60Hz motor will deliver:
HP=.746 x sqrt3 x E x I x PF x EFF/1000 =  79.7 x PF x EFF
2. 380V 50Hz motor will deliver:
HP=.746 x sqrt3 x E x I x PF x EFF/1000 = 49.1 x PF x EFF
Assuming that Efficiencies EFFs and Power Factors PFs of both motors are the same, the first motor will deliver more HPs.\\\

RE: actual work 380V vs 460V

In much simpler terms power includes product of voltage AND current. You need to know both the Current and voltage to determine the total power.

For 3 Phase system kVA = (sqrt 3)*V*I

kW = kVA*power factor = real 'Work"

HP = 0.746 kW
You can use the above relationship for a 3 phase motor.

What you will get by above calculation for a motor is input to the motor. The output of the motor is input*efficiency

RE: actual work 380V vs 460V

correction:

kVA= sqrt (3)*kV*I or Sqrt(3)*V*I/1000

RE: actual work 380V vs 460V

Correction, I beg your pardon:
1. 460V 60Hz motor will deliver:
HP=(1/746) x sqrt3 x E x I x PF x EFF = 107 x PF x EFF
2. 380V 50Hz motor will deliver:
HP=(1/746) x sqrt3 x E x I x PF x EFF = 88 x PF x EFF
Assuming that Efficiencies EFFs and Power Factors PFs of both motors are the same, the first motor will deliver more HPs.

RE: actual work 380V vs 460V

The electric input of a circuit is; Total Power= Volts * Amps
For three phase circuits KVAin= 1.732*V*A/1000

For your post values:

    KVAin1 = 1.732 *460*100/1000 = 79.674
    KVAin 2 = 1.732*380*100/1000 = 65.817

If you want to know the power delivered in the motor shaft , the efficiency (EFF) and the power factor (PF) of that particular motor is needed. If we assume same figures EFF=0.90 and PF=0.85.

    KWout1 = 79.674*0.90*0.85 = 60.95 (KW)= 81.7 (HP)
    KWout2 = 65.817*0.90*0.85 = 50.35 (KW)= 67.49 (HP)

RE: actual work 380V vs 460V

Suggestion: This size of motor tend to have better efficiency and power factor than .9 and .85. Visit for example:
http://www.baldor.com
for similar-motor specs

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources