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  • Users: 7JLAman4
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  1. 7JLAman4

    Calculation of Equivelant Impedance

    I'm attempting to calculate Zeq at the buss level. I have three generator impedances (Z1, Z2, Z3) connected in parallel and the cable impedances (Z12, Z23) connecting each of the generator busses. How do I calculate Zeq at the buss? Are they all in parallel or something else? Z1 nodes 0-1 Z2...
  2. 7JLAman4

    Safety Procedures

    Not certain if this is the place to post, but...I'm looking for something that I might be able to better help me pull together a document for a land based test site electrical equipment (panels, cable) installation that identifies procedures related to safety, commissioning/checkout...
  3. 7JLAman4

    Transformer Wiring

    Is it possible to rewire a single phase isolation transformer to provide a 1:2 voltage output ratio.
  4. 7JLAman4

    General VFD Question

    General question regarding PWM VFD (inverter)operation. Using the constant torque setting (V/f), does the input current of the inverter increase as the output frequency increases? and if so, then is it proportional to the output frequency?
  5. 7JLAman4

    Calculation Method of Unbalanced Panel

    I have a 3-Ph 120VAC Delta connected power panel. I was given a method for calculating/estimating the panel feeder cable 3-Ph load ampacity. My question is, how accurate is this method below? The 3 phase load was calculated as follows; for an unbalanced load on a panel, add the two highest...
  6. 7JLAman4

    Motor and Drive Selection

    I'm looking for assistance dealing with a motor configuration. I'm looking for ideas regarding continuous low speed operation of an induction motor, or what I think is low speed. The required motor is 700Hp at 100 rpm. I've got a supply voltage of 480VAC 3Ph 3Wire (delta). What I'm thinking...
  7. 7JLAman4

    Required Cable/Protection of Unbalanced 3Ph Panel

    What is th proper method of determining the required/calculated cable ampacity of an unbalanced 3Ph panel. Assume a 3Ph-3W delta configured panel that has 15kVA PhAB, 10kVA PhBC and 12kVA PhCA. I understand the method of calulating line currents of unbalanced systems, but what is the...
  8. 7JLAman4

    Power Panel Loading Calculation

    I have the following 120V-3Ph-Delta panel that contains the following phase loading: AB: 5.3A CA: 13.0A BC: 11.2A How do I calculate the feeder ampacity? The drawing that I have shows a 21.0A load. Not certain how this number was calculated.
  9. 7JLAman4

    Creating Coefficient of Utilization Table

    How is the Coefficient of Utilization table created from the candela information in the IES standard illuminance files? Many manufactures are providing the IES files with the fixtures. How are these values used when performing quick dirty handcalcs using the Zonal Cavity method?
  10. 7JLAman4

    Zonal Cavity Lighting Calculation

    Re: the Percent Effective Cavity Reflectance table. I'm attempting get a better understanding how to determine or calculate the values that are presented in this table. I understand that the method or formula that is used to derive the presented values is linear which allows linear...
  11. 7JLAman4

    Battery Bank Configuration

    Somewhat new to the battery arena. I'm looking into a system that utilizes (2) identical battery banks paralleled charged from a single charger. Do I need any isolation between the banks preventing one from draining the other? The charger does not support multiple outputs, but is rated for...
  12. 7JLAman4

    AC Motor Supply Wye Delta

    I have a simple question/inquiry. I'm determining the stator supply configuration for a 6.9kV 3-Phase 12-pole squirrel cage induction motor. What are, if any, the pro and cons to supplying the stator with a WYE connection that does not utilize the neutral vice a Delta connected stator?
  13. 7JLAman4

    Cable Voltage Drop equa

    I'm looking for some assistance re: cable voltage drop of a 3-Ph Cu cable 416300CM 405' 450VAC with 260Amps. Normally for simplicity, the following formula has been used: VD% = sqrt(3) (12 x I x L x 100) / (CM V) What is the more precise method for determining cable voltage drop given the...
  14. 7JLAman4

    Electrical Cable Installation Concern

    I have watertight cable types running thru a Quazite box that collects a fair amount of water that reaches above the cables. What electrical issues might/will I have occurring?
  15. 7JLAman4

    Tranformer Power Calculation

    The formula for an unbalanced Wye transformer output is as follows: I(L) = SQRT[I(A)^2+I(B)^2+I(C)^2-[I(A)I(B)]-[I(B)I(C)]-[I(C)I(A)]) What is I(L)? In a balanced Wye system, I(L) = I(Ph). This equation given for an unbalanced Wye load is puzzling. At what location would this be measurable?
  16. 7JLAman4

    Sizing of Feeder Circuit with Interlocked Loads

    I'm looking for NEC requirements for sizing of feeder circuits that supply panel loads that are interlocked and not permitted to operate concurrently. Not sure if I have seen this requirement previously, but currently looking for a reference to allow "derating" of the required feeder circuit...
  17. 7JLAman4

    Medium Voltage Safety Precautions

    Looking for safety standards related to medium voltage 1kV-15kV distribution systems when fire fighting, general maintenance and protection (boundaries, locking mechanisms, etc).
  18. 7JLAman4

    Addition of 3PH and 1PH loads

    If I have (1)36kVA 3PH load, (1)10kVA 1PH-A, (1)15kVA 1PH-B and (1)15kVA 1PH-C loads, is my total effective kVA load 36+15+15+10= 76kVA for sizing a generator to supply them (assuming they are operating simultaneously).
  19. 7JLAman4

    Calculation of Unbalanced Transformer Loads

    I'm attempting to calculate the Line currents (with no sucess) of a 120V Delta transformer secondary with 3,4 & 5 kVA on phase windings A, B & C respectively with a phase sequence ABC. I originally started out with a 15kVA 3Ph load (5kVA per phase) and knowing how to calculate for a balanced...
  20. 7JLAman4

    Calculating Equivelant Power of 3 Phase Delta system

    On a 450/120V delta system where on windings A, B & C, 2.25, 2.4 & 2.2 kVA are connected respectively. What is the equivelant 3 phase kVA or kW that is seen. Based on these numbers, (3) 3kVA transformers were selected (loading not more than 80% of winding rating). Ratings of the single phase...

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