1 / 9

Three Phase Power

Three Phase Power. Phase Unbalance. Phase Unbalance. A full three-phase supply is recommended for all three phase motors , consisting of three individual transformers or one three phase transformer.

conley
Download Presentation

Three Phase Power

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Three Phase Power Phase Unbalance

  2. Phase Unbalance • A full three-phase supply is recommended for all three phase motors, consisting of three individual transformers or one three phase transformer. • Delta or Wye connections using only two transformers can be used, but are more likely to cause problems, such as poor performance, overload tripping or early motor failure due to current unbalance.

  3. Checking and Correcting Rotation • Establish the proper direction by running the motor momentarily and observing the blade direction or the pressures from the compressor. • Rotation can be changed by swapping two of the line power leads. (TURN OFF POWER BEFORE DOING THIS)

  4. Checking Current Unbalance • After correct rotation has been established, check the current draw on all three of the motor leads and calculate the current unbalance. • If the current unbalance is 2% or LESS leave the leads connected.

  5. To calculate percent of current unbalance: • Add the three line amps values together. • Divide the sum by three, yielding • average current. • Pick the amp value which is furthest from the average current (either high or low). • Determine the difference between this amp • value (furthest from average) and the average. • Divide the difference by the average. Multiply the result by 100 to determine percent of unbalance.

  6. EXAMPLE: • T1 = 51 amps T3 = 50 amps T2 = 50 amps • T2 = 46 amps T1 = 49 amps T3 = 48 amps • T3 = 53 amps T2 = 51 amps T1 = 52 amps 150 amps = 150 amps = 150 amps 150/3= 50 150/3=50 150/3=50 50-46=4 50-49=1 50-48=2 4/50=0.08or8% 1/50=0.02or2% 5/50=0.04or4%

  7. Current unbalance should not exceed 5% at max amp load or 10% at rated input load. • If the unbalance cannot be corrected by rolling leads, the source of the unbalance must be located and corrected. • It could be power side or motor side, you will have to determine the source.

  8. Some manufacturers have “phase unbalance” protection in their light and heavy commercial units that constantly monitor the phase unbalance of a unit, and will shut the machine down if it goes past the limits.

More Related