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  • Users: xj25
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  1. xj25

    Electric motor type relative figures

    Hi everybody, I took some time to compare some motor series catalogs from ABB, Leroy Somer and WEG (see link below), so to gain some insight in present days industrial grade motors, comparing motor type and size vs nominal ratings. In efficiency you can find IE4 options of any type, for IE5 it...
  2. xj25

    Rewinding AC Inductors used at different voltage

    Hi everybody, This is question both related to a job retrofit issue, but also for hobby project applications for reusing old cores from PCBs, old appliances etc., I want to better understand how to reuse an iron core for inductor rewinding and application with different AC input voltages...
  3. xj25

    DoE report on Benchmarking EV and HEV Technologies (inc. efficiency data of drives and motor types)

    Hi, Searching for info on the BMWi3 drive I run into this report, I thought that could be of interest to share...
  4. xj25

    Bearing brinelling

    Hi everybody, We have had a requirement from a motor supplier (induction, 200kW range), about the need of inmobilising the rotor in longitudinal direction, to avoid brinelling problems in the bearings. This is to apply once the motor is mounted on the machinery we build. We have had lots of...
  5. xj25

    Ventilation balance with different pressure drop and flow requirements

    As I don´t see a lot of activity in the ventilation forum, I would ask if someone can make some comments/suggestions to the following thread, thanks in anycase thread1043-416400
  6. xj25

    Water cooled induction motors, review and discussion of Tesla model S motor

    Hi, after seeing a video of Tesla Model S drive and some impressive specs I have done a little of investigation in currently in production water cooled induction motors. I took 250kW 4pole as reference for comparison, and found the following typical specs for some motor builder datasheets...
  7. xj25

    well posed boundary conditions for HVAC grilles

    Hi everybody, We are working in a system with an HVAC duct with two outlets, something like in this sketch Our consultancy uses a model applying the following BC: set the inlet flow fixed, and P=0 at the front surface of the plate holes and slots (almost aligned with the duct wall). I don´t...
  8. xj25

    Highest grades in adhesion railway

    Hi, I am looking for info regarding regular service routes with high grades (>3.5%) in adhesion type railways, and brake types & solutions associated with them. i.e. this link in wikipedia Link I see several regular service lines in switzerland, the Docklands Lightrail in London and a HSL in...
  9. xj25

    Opinion about fissured diode packages (w/ pictures)

    Hi, We have had some faults (last year like 3 in total 60 equipment) due to a diode failing in open circuit. It is on top of a DC control circuit just after the MCB, and has the function of avoiding reverse supply to upstream circuits. The diode is 3A RMS and after checking we have seen some...
  10. xj25

    Resonant DC/DC basics

    Hi, I have a doubt regarding isolated resonant DC/DC topologies. I understood that for keeping the resonant mode the input and output converters shall be in some way synchronised. With the attached block diagram from a Auxiliary DC PS supplier, how do you get that with a rectifier in between...
  11. xj25

    Small installation problems, compressor size and condensation

    Hi guys, We have an auxiliary pneumatic system for service about 5000h hours/year supplied by a 100L/min oilless recip. consisting in: cp from atm to 9bar - pulsating damper+discharge valve - safety+check valve - 40um filter+timed drain - 20L reservoir+timed drain - 5bar regulator - end...
  12. xj25

    h forced convection correlation, frontal plate

    Hi, hc=25W/m2K is a value frequently used for forced convection for calculating overall heat transfer coeficients for windows, walls etc. It is referenced in various regulations, EN and ISO. I have been looking from where this value comes, and some sensible way of linking it to the so called...
  13. xj25

    Power supply noise, how can I get rid of it?

    Hi guys, I have a 300kHz RF amplifier working (see thread248-366918 for info), but my small TRACOPower +15/-15Vdc SMPS is coupling a terrible 2 MHz noise up to 3-4Vpeak all over the circuit nodes (from PS, input and output). The schematic is something like: 220AC - 24Vdc SMPS Carlo Gavazzi...
  14. xj25

    Signal generator curent source 1MHz / 1A

    Hi, I need to measure a stray inductance in the range of 5uH to 0.1uH at a current of about 1A. I thought of designing an small current source amplifier with a signal generator 5Vp input. Freq. to be used is planned fom 100kHz to 1MHz. I will inject a 1MHz/1A waveform So then I will measure...
  15. xj25

    Overall heat tr. coef. from measurements, "quick" procedure with mistereous factor

    Hi, I found this russian norm extract where a "quick" procedure for overall heat transfer coeficient (K in the document) stimation in heated cabins is given. Basically it says: - set up some kW of heaters, and internal and external T sensors. - let wait about 1.5-2h to reach what it calls...
  16. xj25

    Shortcircuit scenario and need of a crowbar device

    Hi Guys, We have an application in which there are a 750Vdc and a 24Vdc circuit connected by a normally open sectioning switch, and protected by a quick acting fuse (Protistor type). The 24Vdc circuit is always energized, supplied from a 260Ah NiCd battery. The 750Vdc circuit is not energized...
  17. xj25

    Relay DC rating at different voltage

    Hi everybody, I have an equipment with an integrated output relay with the following characteristics (from eq. datahseet, i could not know relay datasheet): 5A 30Vdc resistive load 5A 230Vac resistive load I need it for a custom application to switch 90Vdc, load <20mA (high impedance digital...
  18. xj25

    MTBF of n redundant of N equipments

    Hi, I am looking for a closed formulae or method for getting the composed MTBF of m redundant equipments of N total. I.e. 8 pumps, I need 6 working to do the job. MTBF of 1 pump is X, What is the MTBF_6_of_8_pumps_working? I got this formula from "introduction to reliability engineering" of...
  19. xj25

    Start up transients in isolated engine-generator group.

    Hi guys, I reviewed yesterday a problem in an isolated diesel motor-synchronous generator group ("island" system). The generator supplies to a compressor and a battery charger. Basic motor diesel data: - 800rpm nominal. - uses a hyrdotransmission to regulate the power to the generator. - limit...
  20. xj25

    N1 stator turns

    Hi, I have been messing with an self-made induction motor equivalent circuit model (just regular steady state circuit). I got some results using circuit data from a real motor datasheet but I had to guess the values for N1 (stator turns per phase) and N2(rotor bars) because I don´t know them...

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