What Is the Correct Current Draw Calculation for a 2Hp 208V 3-Phase Motor?

Click For Summary

Discussion Overview

The discussion revolves around calculating the current draw for a 2 Hp 208V 3-phase motor, focusing on the mathematical breakdown necessary for sizing wires and fuses in a schematic. The context includes electrical calculations and considerations for power factor and efficiency.

Discussion Character

  • Technical explanation
  • Mathematical reasoning
  • Homework-related

Main Points Raised

  • One participant, Matt, seeks assistance in calculating the current draw for a 2 Hp motor, initially calculating 862 A, which he acknowledges is incorrect.
  • Matt calculates the current draw using the formula P(watts) = I(Amps) * v(volts) and arrives at 7.17 A per phase based on 1492 watts and 208 volts.
  • Another participant questions whether the 1492 W represents total power and suggests that it may need to be divided among the three phases before applying the P=IV calculation.
  • A later reply indicates that Matt's calculation is correct for a single-phase motor but notes that for three-phase calculations, the result should be divided by the square root of 3 (approximately 1.73).

Areas of Agreement / Disagreement

Participants do not reach a consensus on the correct approach for the three-phase calculation, as there are differing interpretations of how to apply the power calculation in this context.

Contextual Notes

There is uncertainty regarding the application of the power calculation for three-phase systems, particularly in how to handle the total power distribution across phases. The discussion does not resolve the mathematical steps necessary for the correct calculation.

Matt1234
Messages
141
Reaction score
0
hi there,
Looking for some info, on how i would find the current draw of a 2 Hp motor running at 208v 3 phase with a unity power factor and efficenty of 100%. I can't seem to put it together today and cannot get ahold of a TA, basically i need to size wires/fuses in a schematic for this current draw and completely forgot how to do this. I keep getting 862 A which i know is way too high. I know 2 hp = 1492 watts. Can someone please help me with the mathematic breakdown? Would be appreciated.


i think I am losing it been a real bad week for me.
I think can use this:

P(watts) = I(Amps) * v(volts)

1492 = I * 208
I = 7.17 A per phase?

Is this correct?


Thanks,
Matt.
 
Physics news on Phys.org
Anyone?
 
This is not my field of expertise, but I am wondering if the 1492 W is the total power, and should be divided up among the 3 phases before doing the "P=IV" calculation?
 
Your calculation is correct for a single phase motor. For three phase you need to divied by 1.73 (square root of 3).
 

Similar threads

Engineering How to calculate rotor flux of the three phase squirrel cage induction motor?
  • · Replies 4 ·
Replies
4
Views
3K
What is the correct method for counting poles in a 3-phase induction motor?
  • · Replies 4 ·
Replies
4
Views
4K
Engineering How Do You Calculate Current and Power Factor in a Synchronous Induction Motor?
  • · Replies 4 ·
Replies
4
Views
4K
Engineering How Does Reducing Excitation Affect a Synchronous Induction Motor's Performance?
  • · Replies 4 ·
Replies
4
Views
3K
What Could Be Causing My 3 Phase Motor to Lack Power and Torque?
  • · Replies 23 ·
Replies
23
Views
7K
Engineering Line Current for 30kW 3 phase motor
  • · Replies 2 ·
Replies
2
Views
14K
Engineering P= 1.732 X 230V X 42A X 0.85 = 10,731.06 W or 10.73 kW
  • · Replies 7 ·
Replies
7
Views
3K
Engineering Electrical Machines and Power Electronics - 3 phase, 6 pole induction motor
  • · Replies 1 ·
Replies
1
Views
4K
Calculating Three Phase Power Load: Help & Homework Statement
  • · Replies 2 ·
Replies
2
Views
4K
How Does Power Factor Change with Field Induced EMF in a Synchronous Motor?
  • · Replies 1 ·
Replies
1
Views
3K