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  1. lakevillethor

    dum question: v = Ldi/dt

    I didn't really articulate what I meant very well. What you said is what I meant. -AT
  2. lakevillethor

    dum question: v = Ldi/dt

    Gentlemen, Thanks for all your responses. After going over this time and time again, one thing is clear...the voltage spike will occur when the circuit is opened. One more question...In steady state conditions will an inductor act as a short circuit? I know that an inductor acts a short...
  3. lakevillethor

    dum question: v = Ldi/dt

    Peebee, I understand that the current lags the voltage in an inductive load. But you just said it..."On energization, there is an INRUSH, not a slow increase in current, but rather a sudden high level of current." Are you certain about the inrush of current? If the inrush of current...
  4. lakevillethor

    dum question: v = Ldi/dt

    I don't know what you mean by voltage notch...I am going to talk my way through a step by step pocess of what happens. Please correct me if I am wrong. Okay, so you wire up your switch and your inductor and at time 0 you throw the switch. 1: 240 VAC is applied across the inductor 2: The...
  5. lakevillethor

    dum question: v = Ldi/dt

    That's what I am saying; they are at the same node. My boss told me different and that the voltage would increase as a function of the L di/dt. I find that unlikely. So, in short, there would be no spike when the breaker was flipped on. The spike in voltage comes from the rapid decceleration...
  6. lakevillethor

    dum question: v = Ldi/dt

    Let me ask this question then...If you had an inductor and you hooked it up to a circuit (say 240 volts AC), would you initially get a voltage spike (higher than 240) across the inductor when you flipped the switch ON? Moreover, since the current cannot change at one instant of time, is it...
  7. lakevillethor

    dum question: v = Ldi/dt

    thanks everyone. I think I got it now. -Andrew Thoresen
  8. lakevillethor

    dum question: v = Ldi/dt

    Thank you all for posting - this discussion is really helping me understand it throughly. I always knew teh mathematical formulas - sadly this was enough to get my by school without having to understand it thoroughly. Let me set up an example and see if this is exactly analagous to the voltage...
  9. lakevillethor

    dum question: v = Ldi/dt

    thanks for all your replies, fellas. Dan could you please go into more detail. I almost have it. IS this situation analagous to momentum? -AT
  10. lakevillethor

    Strange Voltages

    Open delta configuration. It's a vector diagram. 208 = 120 * (sqrt of 3). -AT
  11. lakevillethor

    dum question: v = Ldi/dt

    Fellas, I am having trouble understanding a basic concept. What I would like to know is how, via what mechanism, the voltage spikes in an inductive load. Lets say that you have an inductor hooked up to 240 VAC. The voltage will raise according to the rate of change of current times the...
  12. lakevillethor

    Finding complex impedance of AC unit...

    jghrist, Can you elaborate a little more on what you were talking about, por favor. Thank you. -Andrew
  13. lakevillethor

    Finding complex impedance of AC unit...

    I appreciate your help. Then here's my new question, do I use the RLA to find the complex impedence of the device? Moreover, should I use the 27.8 figure corresponding to the RLA figure and calculate the Z value? If so, that would give me a Z value of 8.633? I think you see where I am going...
  14. lakevillethor

    Finding complex impedance of AC unit...

    You said "FLA Full Load Amperage. This is the maximum sustainable current draw. The circuit must be able to handle this all day on a hot day. Typically the max amps and hot day will coincide. The system breaker and wiring must be rated at this or higher." I don't understand how...
  15. lakevillethor

    Finding complex impedance of AC unit...

    Bro, there is no lawsuit pending here and I am doing the grunt work for my boss who would testify.
  16. lakevillethor

    Finding complex impedance of AC unit...

    Thanks for the heads up on the NEC.
  17. lakevillethor

    Finding complex impedance of AC unit...

    Lastly, in application, this AC unit is thought to have triggered an electrical event which started the fire. There was a screw through a wire nut. The screw did not penetrate all of the insulation in the wire nut when it was installed. Instead, a year later, when the main was switched ON, I...
  18. lakevillethor

    Finding complex impedance of AC unit...

    single-phase - 240 V. Here's the stats on it: Max fuse or HACR type breaker amps...60 LRA...130; FLA...1.7; RLA...27.8;
  19. lakevillethor

    Finding complex impedance of AC unit...

    The grim reality is that the people I work with never understand what I am asking them - perhaps I am bad at articulating what I am trying to say. Okay, I appreciate all of your help. Here's the application. I am an electrical engineer who works in forensics; I investigate electrical fires...
  20. lakevillethor

    Finding complex impedance of AC unit...

    Fellow engineers, I need some help calculating the impedance of an Air Conditioning unit. I have the RLA (run load amps), FLA (full load amps) and LRA (locked rotor amps). It is a 240 unit. Are these ratings complex? Moreover, are these ratings given in sqrt (R^2 + X^2) or is it just r? any...

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