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What is the minimum ampacity of the branch circuit conductors for a 25 HP , 480-volt, 3 phase, squirrel cage motor with nameplate FLI of 32.5 amps ? Name Plate value not used 430.250: 25hp @480v = 34 amps 430.22(a): 34 X 125% = 42.5 amps 310.15(b)(16) : # 6 THHN @60oC and 55 amps. Step 1.
This course treats the subject of three phase power in detail and in a manner that a reader, well experienced in three phase circuits or otherwise, will find easy to follow. The course considers all of the possible types of three phase circuits - balanced, unbalanced, three wire, four wire, wye and delta circuits.
Phasor representation simplifies circuit analysis when dealing with sinusoidal signals. Drop the time-harmonic (oscillatory) portion of the signal representation. Known and constant. Represent with rms amplitude and phase only. For example, consider the time-domain voltage expression.
3-Phase Power Formula. Here’s the simple formula we use to calculate power on a 1-phase AC circuit: P (kW) = I (Amps) × V (Volts) ÷ 1,000. Basically, we just multiply amp by volts. The ‘1,000’ factor is there to convert from W to kW; we want the resulting power to be in kilowatts. 1 kW = 1,000W.
Three-Phase Power – Example. Calculate the line-to-line voltage from the line-to-neutral voltage 𝑽𝑽𝑨𝑨𝑩𝑩= 3𝑽𝑽𝑨𝑨𝑨𝑨∠30° 𝑽𝑽𝑨𝑨𝑩𝑩= 156∠14.3°𝑉𝑉. Alternatively, we could calculate line-to-line voltage from the two line-to-neutral voltages. The line-to-neutral voltage at phase 𝐵𝐵is.
NEC CODE RULES. Breaker/Fuse Ratings Conductor Ampacity Equipment Grounding Conductor Grounding Electrode Conductor. Motor Conductor Size. Motor Short-Circuit Protection Transformer Overcurrent Protection. 240.6(A) 310.15 and Table 310.16 250.122 250.66 430.22 (Single) 430.24 (Multiple) 430.52 450.3.
First the measured I1 and the measured phase power PPH are used to calculate. PC + PFW = PPH − I1 2R1 , where I12R1 is the copper loss in this no-load case, PC [W] is the per-phase core loss and PFW [W] is the per-phase friction-and-windage.
