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    LED Drivers?

    Typically I see a LED circuit consistng of the LED and a current limiting resistor in series with a power supply. Why, and when are current limiting regulator circuitry used? In these new LED flashlites, is it just a LED, resistor and (4) AAA cells, or is there some active...
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    Frequency and Voltage change for elektromotor

    VFD Mc Master Carr, page 869, Cat# 116. Gleason VFD 1/4- 1 hp. 3 phase AC Motor speed Controller. $332.47. I've used these they work great for small motors
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    Acopian Model K20D50 Power Supply sschematic needed

    I recently aquired an Acopian Dual, Regulated, Current limited supply: Model K20D50. Can any one supply me with a schematic? Thanks, Eddie
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    Thermistors used for in rush current limiters

    Has anyone experience with using thermistors for in-rush current limiting. I see them used in power suppies on consumer electronic EPCOS manufactures them and Newark Electonic distributes. Where can I fin application data, so I can build and use for repaiing equipment Eddie
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    Voltage Dependent Resistor

    I think I found ithe answer: http://www.epcos.com/web/generator/Web/Sections/ProductCatalog/Sensors/TemperatureMeasurement/ApplicationNotes/02__InrushCurrrentLimitingAN2/PDF__InrushCurrentLimiting__AN2,property=Data__en.pdf;/PDF_InrushCurrentLimiting_AN2.pdf The device is a NTC Thermister...
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    Voltage Dependent Resistor

    I noticed bigger VFD's (5 Hp and up) use large inductors to filter incoming line spikes. I guess the MOV is an alternative. I always seen MOV from L1 to L2, and or to ground. Never in series with the line, but why not?
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    Voltage Dependent Resistor

    Neither have I Chris, The circuit board has it labeled R1.The outside coating was cooked but it looked like whats left of an MOV. Like a big disc capacitor. It is definitely in series with L1. The 110VAC is applied thru R1 (the MOV) to the primary of a 1;1 Torroid xfmr. The...
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    Voltage Dependent Resistor

    More on VDR, MOV's, thermistors I have a kit called Globar resistors for deqauss circuits. FRTV5 There are two "resistors" consisting of a thermistor and a varistor. One is black coated the size of a quarter, the other is smaller than a dime, silver in color. Which is the thermistor...
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    Motor type?

    Another issue you need to be concerned with: when using a motor with a VFD is cooling the motor. Most motors used with VFD's are Inverter rated/duty. This means theyhave higher winding insulation rating and when operating at a reduced speed the integral fan moves enough air to cool the...
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    Voltage Dependent Resistor

    I' ve seen VDR's used in televison deguassing circuits and now in a power supply. It is wired in series with the AC line feding a transformer which feeds a Bridge rectifier. How is the VDR sized in the powersupply cicuit. Can it be replaced with a slo-blow fuse?
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    Boat Lift VFD Controller

    I have a Reinmann & Georger Corp., VL Direct Drive Compact Guard, Boat Lift Hoist. It uses a 3 phase 230VAC, 2.4A, 3/4HP motor and VFD drive circuitry. The circuitry experienced an overvoltage surge. It burned (charred) R1, a VDR (voltage dependent resistor). In its charred state the R1...
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    need help finding a male terminal block

    I believe it might be: MC Series Euro Style terminalblock Mfgr p/n: MC200-5009 9 poles Newark Electronics Catalog 129, Page 1085 1-800-463-9275 Newark P/N 04R6913 $4.06
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    VFD Keeps Dying

    I'm not sure if it would do a lot of good, but as acheap insurance I was thinking of putting a service entrance type surge protector ahead of my VFD. I would think the inductors inside the VFD would catch a lot of transiants, but obviously they didn't protect my unit. I'm using...
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    VFD Keeps Dying

    Put a voltage data logger on the incoming line. I had a EATON unit fail intermittently. It turned out the power company had several over voltages on the line. The final one (during a storm) took out one leg of the 3 phase rectifier, and the output thyristor block.
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    A question about audio output impedance

    To Electrician: I looked up the two references you pointed me to. Excellent! And your answer of "yes" to nominal values was what I was looking for. The graphical image of open and short cicuit impeadances was most interesting. My experiments proved I don't have an "ideal "...
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    A question about audio output impedance

    Part of my error was I was using only 1/2 the winding: the center tap to one side. Also my voltage ratio is actually 19 v / .5 or 38. 38 X 38 = 1444. 1444 X 8 = 11552 which is closer to the spec of 10,000. I'm thinking measurement error accounts for the discrepancy. I put a 10 ohm...
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    A question about audio output impedance

    Impedance matching The transformer spec is printed on the housing: 10,000 ohms Plate to Plate. The formula Z out is the turns ratio squared times Z in,, what I want to do is measure it. I tested the transformer at both 400 and 1000 HZ. The ratio is the same. My next test will be 8...
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    A question about audio output impedance

    I’ve been studying audio output transformers and experimenting. I’m using a Chicago A-3831 Universal Output transformer. The transformer spec’s indicate 10,000 ohms plate to plate, center tapped, primary and multi-tapped secondary. (I’m using the 8 ohm tap). Using my HP 200...
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    AC Choke question

    My variable frequency drive has an AC choke in each leg of the 3 phase mains.I uderstand the chokes are for keeping interferance from entering or exiting (backfeeding) the mains. Do the chokes provide any other benifits? (Regulation, etc?) Thanks
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