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  1. Evening gents, I'm trying to pick out MOSFETs along with a MOSFET Gate Driver from International Rectifier that will suit my needs. (See http://www.irf.com/indexsw.html) The MOSFETS will be used in an H-Bridge configuration, with the MOSFET Gate Driver driving the gates of each respective MOSFET. This circuit will be used for a motor controller. The batteries used to power the motor are Lithium Polymer batteries manufactured by GBS batteries. The batteries have sixteen 3.6V cells connected in series to have a rated voltage of 55V and a capacity of 60Ah. The motor is a permanent magnet brushed DC motor from Motenergy, model part number ME0708. The motor has a lead to lead resistance of 0.01Ω, and a lead to lead inductance of 0.055mH at 120Hz. The motor is rated for 48V and 100A, but can handle up to 300A for one minute, and has maximum peak torque of 37.8 Nm and maximum rotor speed of 5000rpm. A switching frequency of ~15kHz is assumed. The datasheets for both the motor and LiPo battery bank are attached below. 1) What part number MOSFETS would do you recommend I use? Also, for my current requirements (i.e. up to 300A for one minute) should I use multiple MOSFETs in parallel, or opt out for a single MOSFET with higher current carrying capabilities? 2) What part number MOSFET Gate Driver would you recommend I use? Assume the MOSFET Gate Driver will be driven from a 12V supply. Thanks again for all your help and any suggestions/advice/recommendations you may have for me! EDIT: What I've found so far, 1) Placing two of these MOSFETs in parallel, http://www.irf.com/product-info/datasheets/data/irfp4468pbf.pdf ME708_Mech.pdf ME708_Perf_Curves.pdf GBS_60AH_Specifications.pdf
  2. Evening gents, Attached is schematic of a motor controller I am looking to modify and implement. As a start, I've been reading through the datasheets of the IC's and began looking the the external resistors and capacitors to try and figure how the particular R and C values were selected. 1)I started with the string of three resistors at the output of the LM7805. This string of resistors gives a voltage value between 0.202-4.79V at the top of C2 depending on the position of the wiper. Is there any particular reason a value of 202Ω is moreso convenient than any other resistor value? 2)Can someone help me clarify what the role of R4 and C2 is? From the terminals of the microcontrollers ADC pin it looks as though it is a LPF, with a cutoff frequency of, f3dB = 3.39Hz 3) Is R7 (the 4.7kΩ resistor on the input pin of the MOSFET gate driver) for limiting the current to ground in the event of a short or fault on either side of it? 4) Again we see what seems to be an RC LPF looking from the enable pin of the gate driver outwards, is that what this circuit is for? Here I calculate a cutoff frequency of, f3dB = 3.60Hz 5) Moving over to the output portion of the gate driver we see voltage dividers across the gate-source junctions of the MOSFETs. From the datasheet of the gate driver, we note that VOH=Vcc-0.025 = 11.98V, and from the voltage divider formed by the 30Ω and 100kΩ resistors we find that, VGS ~ 11.98V 6) If we assume Vss = 72V, and that C5 is constructed by a parallel string of twelve 470uF caps, how do I go about figuring out the drain current through each MOSFET? Also, why is the string of twelve 470uF caps needed? 7) It has also been suggested to me that some 22kΩ safety resistors should be added from the gate of each MOSFET to ground in the event that the gate driver fails. It was mentioned that the MOSFETs gate voltage would drop to around 5-7 volts if the driver quit working, keeping the MOSFETs on until they burn out. How do they figure that the gate voltage will be 5-7 volts? Thanks again for all your help!
  3. Hello, I'm looking to build my own lab power supply, but am still fairly new to the "practical" aspects of electronics.(i.e. wiring circuits up to mains voltages) I've taken two university level courses on electronics, but I still feel I have a lot to learn. (Currently reading "The Art of Electronics") Is this a good first power supply project for me, or should I go for something easier to start with? If so, is there a "latest and greatest" version of the schematic and BOM? Thanks for your input!
  4. See attached figure for design requirements. I decided to experiment, solving the outcomes of L, C, ΔiL, IL and R given a selected frequency, input voltage and output voltage. Of course to obtain the values of the outcomes in a simple manner I made various assumptions. These assumptions are stated below, Assumptions: [*]Diode and Transistor voltage drops are 0 [*]Minimum output current = Output current, In other words Imin = 0 (We are operating on the edge of CCM) [*]The value for the output current was always selected such that the output power was 100W. **NOTE: We are neglecting the power dissipated across the series resistance of the source (i.e. Prin = IL²D²rin) because for all values of IL and D I found this to be small in comparison to the 100W. Attached below is a figure of the table of outcomes. Are my assumptions "valid enough" that these results have actual relevant meaning and/or insight? Can someone help me interpret my results? Am I moving in the right direction?
  5. Is that it's main application? I've also read that is used for stabilizing when a short occurs.
  6. As the title so bluntly states, what's the purpose of a Reactor? I'm an engineering student and the group I'm currently working for does lots of consulting work for a number substations and what I've often seen in the project descriptions is things like, "Reactor Salvage & Replacement", but I don't even know what a Reactor is(or does)! ??? Good thing I'm not doing the design work just yet! ;D Anyways, can someone give me a better idea of what a reactor is used for, and what it does? (If it's in the context of substations, even better!) Feel free to through some circuit diagrams/math equations at me, it usually facilitates my understanding. Thanks again!
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