THE MOLE-X MEGAMOLE

  Scenario: You fall asleep in EGRE 207 and wake up from a prescient dream about futuristic Hyperloop transportation and you suddenly realize that rather than trying to compete by building vacuum levitated vehicle, you can make your fortune by building a better hole, i.e., a better tunnel. So, you form a start-up company, MOLE-X, that is going to build a motorized tunneling device (you’ve dubbed the “MegaMole”, to dig underground vacuum tunnels for future highspeed vehicle travel. You figure Elon Musk is bound to buy out your company and you’ll become a gazillionaire. That’s how the (w)hole dream turned out anyways. Unbeknownst to your parents, you’ve dropped out of VCU to form this start up and spent all your tuition and student loans on parts & equipment to build a state-of-the-art tunneling device in your Manchester loft apartment above the Rebel Yell Brewery. The MegaMole is built using a huge 1 kHP, Romanian 3- AC motor you bought from a Navy surplus junkyard down in Norfolk. Unfortunately, now that it’s complete, your MegaMole is so big and heavy you can’t move it or get it out the door. You desperately need to test it, but the problem is how? How will you even plug it in to 3 power to even start it up? Suddenly you realize that your recent idea to take a late-night security shift at the brewery downstairs in order to get free beer, might actually provide the answer! On your introductory tour, you discovered that the brewery is wired for 3- power and with their open ceilings, you can see that it runs along the ceiling and right underneath your floor. So, you figure hey, we can just lift up a floorboard and tap into that! The problem is that your motor is a huge inductive load, so running it is likely to destroy the brewery’s power factor and jack up their electric bill. If the brewery (a.k.a. your landlord) gets a huge electric bill, they’ll surely notice, shut you down and kick you out before you can strike a deal with Elon Musk. Knowledge: Previous experience with an in-house CBD gardening project taught you that the landlord will not notice a change in the electric bill as long as it’s less than the equivalent of thirty 60-Watt bulbs. So, if you can find a way to compensate your motor and improve the power factor, you should be able to run the MegaMole tunneling machine with the electrical bill looking like less than 30 light bulbs and nobody will be the wiser. But before you decide to try it, you have the brilliant idea to first engage in a feasibility study to see if your scheme can possibly work. First you need some intel, so late one night while you’re on your shift at the brewery you claim you “heard a noise” and go off to “investigate”. Secretly you then measure the 3 power and you find that the brewery power is powered with a 3, Y-Source, and has 240V rms on each phase. Cracking open the rusty old fusebox, you can also see that they have measly 10A fuse on each phase. When you get back to your flat, you google your motor and unfortunately, all the documentation is in Romanian. From one of the cryptic diagrams though, you can see that the motor has a threeterminal connection to the coils that comprise a balanced -load. The spec sheet also shows 416V rms applied to each phase of the motor. The only other information you can glean from the Romanian manufacturer website is an equation next to each motor winding that reads: Z = R + jX = 30 + j75.4  But there is also a notation in Romanian next to that, a box with 50 Hz in the middle of it, so you realize that the standard frequency there must be 50 Hz and not the 60 Hz that we have here in the U.S. Being cautious and also cheap, you figure to try this all out in Multisim Live. That way you are less likely make a mistake that could cause serious bodily harm, property damage, jail time or, more importantly, an end to your free beer. So you begin your MegaMole feasibility study in MultiSim! EXTRA CREDIT LAB: THE MEGAMOLE FEASIBILITY STUDY PART 1: DESIGN 1. Draw a circuit diagram of the Y-Source available from the brewery. 2. Impedance Transformation: If the impedance of a motor winding is given by the Romanian equation at the Romanian standard f =50 Hz: Z = R + jX = 30 + j75.4  What is the equivalent impedance of this individual motor winding at 60 Hz? 3. Load Conversion: Now convert the -load to a Y configuration. a. Draw the D-Load circuit as originally given for 60 Hz b. Calculate the impedance of an equivalent balanced Y-Load to model the 3 AC motor and