Showing posts with label High-Voltage. Show all posts
Showing posts with label High-Voltage. Show all posts

Wednesday, August 03, 2016

Winding Insulation Resistance Measurement

I am working in power plant. we have a problem on one of gas generator. the problem is that low winding insulation resistance of generator rotor. it read 800 k ohm where the other generator read greater than 10 M ohm. at full speed, there is no Kv measurement. same time no standing alarm from excitation system. all equipment are indicated okay.

My question is that is the relation between low isolation resistance of generator rotor and Kv measurement?

Mail from - IB SA Arabia

There is no relation between insulation resistance and any other parameter of you system. Insulation Resistance depends on age, physical damage on windings, humidity, contamination, wear and tear.
Let me know where you are doing the KV measurement. If you are measuring leakage voltage due to insulation breakdown, you have to fix it. The relationship of parameters does not matter. Small leakages can be tackled with grounding, don't compromise on safety and quality.

Dana Tekno Crossmeg Insulation Tester

Dana Tekno Crossmeg Insulation Tester

It is possible you may be touching one of the probes when you measure insulation, that may be the 800K, Even if one finger touches the probe, the circuit is closed via earth and a low 1M measurement can be seen.

The rotor the chassis all need to be grounded, and insulation resistance has to be measured after all power connections or electrical connections are removed. The electrical terminations unit should float for proper measurement, especially when you have doubts. Tell me about your progress.

delabs


I did not get a reply later, but i may not have understood the question well. The question also lacks details. In HV breakdown measurements KV is applied, but it has to be done after disconnecting all points. Beyond a limit, HV testing becomes destructive. Leakage Monitoring and Earth Leakage Breakers can be used. Motor/Generator Protection Units too. Even an imbalance in the current or Three phase problems.

It is best to use a Insulation Tester to apply little above Normal Voltage and see leakage, if this is a routine quality check. Better still, have a current sensor on the earth line and use a data logger to keep a tab on the leakage levels, temperature and voltage of all motors and generators. Even sound/vibration sensors will be an advantage. Before these electrical equipment fail many symptoms can be caught by data logging and limit windows. An electronic instrument or Trip Circuit will operate or alert after a fault occurs. Data logging and analysis will warn of a possible Motor or Generator performance degradation. Symptoms Indicate problems, prevention better than cure. Data Recording, Graphs and preemptive measures better than Breakdown Repairs in the Night. Drop in efficiency is an indicator for maintenace, This also prevents mishaps and power wastage.

It is true some insulation faults will show up on vibration and high humidity levels. These have to be simulated. In operation testing has to be done with sensors and recorders for leakage current etc. not insulation resistance.

Learn more about Insulation testing
- delabs

Saturday, June 11, 2016

SSR Open Circuit Leakage Voltage

hi been trying to use a dc ssr relay to switch 24 volt supply on and off for a unit i use that needs to see 0v or 24v but when the switch voltage is applied there is still 18v showing on the load side not zero ..does the ssr have to have a load on it to fully switch off and on from 0v to 24v ?

Mail from PST in UK


You are right you need a bleeder resistor of 10k or 100k to ensure the collector leakage current of SSR is bypassed to make you see a '0' when the SSR is off. If the SSR is working well, and no input or '0' control input then SSR output is high impedance and only a collector or diode leakage will hold the SSR output at the Full Voltage but it cannot drive any current. Hence a bleeder across output will show you a '0'. Use it if the bleeder does not cause any problems.

Solid State Relays or SSR

If you were driving a 5A Solenoid, then you would not see this problem. If you are driving a Solid State Load, such effects are natural. It is because the Solid State Load like a Electronic Circuit will draw current only on demand.

These instruction is for a Normally Open Output, NO. A Normally Closed NC is vice versa. And also some Special SSRs may have sensitive inputs, So a low impedance '0v' at input has to be ensured.

The Bleeder should bypass the leakage current, so one end of bleeder goes to SSR output and other end of bleeder goes to the ground or 0V point of your circuit which is controlled by SSR.

delabs

They are called SSR as there are made of semiconductors and have no moving parts to wear out. They do generate heat depending on load and switching. Thyristors are used in most as they are rugged, mosfets and IGBT may also be used for various applications.

Solid State Relays or SSR

 In this section you will find SSR designs and PCB layouts which you can study. These were made and sold  by me years ago. So the PCB layouts have gone thru some revisions and they worked quite well.

Wednesday, April 13, 2016

Technology Resource - Silicon Sam

Technology Resource - Silicon Sam

Sci.Electronics.Repair Frequently Asked Question(s) (or S.E.R FAQ for short) Home Page. This site features Samuel M. Goldwasser's latest and greatest "Notes on the Troubleshooting and Repair of..." series of comprehensive repair guides for consumer electronics equipment and other household devices. There is also a great deal of other information of interest to the electronics hobbyist, experimenter, technician, engineer, and possibly even the dentist and poet. Included are the now quite comprehensive and massive "Sam's Laser FAQ".
    Sam's Laser FAQ has a great deal of information on a variety of laser and optics related topics including a comprehensive treatment of diode, helium-neon, argon/krypton ion, and CO2 lasers as well as amateur laser construction including numerous examples of truly home-built lasers. Much of this is not available anywhere else either on-line or in print!

    Home-Built Diode Pumped Solid State (DPSS) Laser

    Home-Built Diode Pumped Solid State (DPSS) Laser

    This generates green light at 532 nm which is not a bad shade of green and quite close to the eye's peak sensitivity. This is the approach used in modern green laser pointers and most modern DPSS green lasers. While other materials can be used to obtain other wavelengths (blue being the most common)

    Monday, January 25, 2016

    Flashing Neon lamp for Soldering iron

    message: How can I make a flashing neon lamp - 240 volt AC

    I have been trying for 3 hours ( R-C circuits) but no success. I want to include it in my soldering iron socket to show the power is on.

    Mail from HJ of UK


    These circuits may help, let me know if this works.

    Neon Lamp Multivibrator ASCII Circuits
      I am sure a reading of above will help make your own. do not forget, i like a feedback.

      delabs


      For the 1 Meg use two 470K in Series for 230V AC, that is safer. The circuit is live, so take precautions. The 0.47 Micro Farad can be increased if you want a slow flash. If the Mains 50/60 Hz Flicker is too much, the 1 uF can be made 2 uF, or use 4 - 1N4007 as a bridge rectifier.
      Flashing Neon lamp for Soldering iron
      From Schematics of delabs

      Flashing Neons (NE-2 / NE-51) second from top

      User Feedback -

      R1 of 4.7M and C2 of 0.47uF Works well at 230V AC. Try your own Combination. Less than 1M may damage Neon.

      Wednesday, December 02, 2015

      Power Oscillator Circuit Design

      I am trying to find a circuit diagram for a long time, which will give me the o/p Characteristics as 12V, 0.5A & 4000 Hz (or variable frequency). Will you please help me in this regard? I will be very very thankful to you.

      Mail from PS

      First make an Oscillator and then Power Amplify it.

      LM675 Power Operational Amplifier

      "The LM675 is capable of delivering output currents in excess of 3 amps, operating at supply voltages of up to 60V. The device overload protection consists of both internal current limiting and thermal shutdown. The amplifier is also internally compensated for gains of 10 or greater. "

      Op Amp Booster Designs  PDF

      "The design of booster stages which achieve power gain while maintaining good dynamic performance is a difficult challenge. The circuitry for boosters will change with the application’s requirements, which can be very diverse. A typical current gain stage is shown in Figure 1."

      Op Amp Booster Designs

      12V, 0.5A & 4000 Hz (or variable frequency) is possible, very high frequencies difficult, for that you have to study RF behavior. Experiment from DC to 1 M Hz, no more with these circuits. 200/300 K Hz if you manage you learn't something. Study pages, learn and try to build it yourself. These links are for learning.

      delabs

      I am extremely thankful to you for your precious reply for my mail. I have tried it to complete the circuit as per your suggestion, but the results are not as per the requirements. Here, I tell you the exact situation. Sir, I am working on the efficiency improvement of an alternator. for this reason I need a frequency generator circuit which will give me the o/p characteristics as 12V, 0.5A & variable frequency upto 4000Hz. The signal must be AC sine waveform. It can be applicable to inductive load. The i/p will be simply 230V AC. Will you please design a circuit for such requirements?

      I am in great need of this. Please, I request you to design it. I will be very very thankful to you.

      Reply from from PS IN

      For professional service, there will be design charge. Your reply will be posted. Anyone who can design this can comment here.

      Unique IC Buffer Enhances Op Amp Designs, Tames Fast Amplifiers

      A unity gain IC power buffer that uses NPN output transistors while avoiding the usual problems of quasi-complementary designs is described. F


      delabs

      Friday, January 02, 2015

      HV and Jacobs Ladder or Climbing Arc

      I mess with HV stuff and recently I went to adjust my Jacobs ladder with it still switch on I griped  each leg of the ladder with my hands . I had a zap  5Kv at 100mA up my arms and across my chest   Why it did not Kill me is beyond my understanding as it is 3 times the accepted lethal power I have made several changes to the set up now including a physical barrier to the wire legs to prevent a re-occurrence

      I will not let my 4 year old Grand son play with the above wooden toy pole pig and helical Jacobs ladder either - I promise

      JAH from USA

      James Howells Spark

      James Howells Spark


      i would be glad if you move away from high-voltage to high-current or online education, your experience may be useful to many.  as far as your survival from the zap, it is the grace of god indeed. do not press your luck too far, even god is very stressed right now.

      The zap takes the shortest path, left hand to right leg, right hand to left leg 100mA can be fatal. If you were wet or sweating, then the surface of the body provides a safer path. Use silicone gloves and good shoes.  Only a Knight in Shining Armour is safe, not for his chivalry but for his conductive coating.

      delabs

      Additional Information about Safety with Electricity

      Never use Smartphone or Tablet while charging (Near Sensitive Ear or Face). You may get electric shock or lightning discharge leaks. Use Surge protected Switchboards and Isolation Transformers or CVT. The mild shock due to Y caps of EMI filters is not a danger.  If the mains adapter you buy is low quality or there is a freak breakdown, you had it.

      The risk is greater when a high voltage leak happens near the ear or face. and Metal parts of the phone gets close to the ear or neck is unsafe. The head and neck have very low resistance and can be damaged with much less Fatal Current.

      Use total plastic exterior phones/tablets, wear shoes and use the speakerphone option when you talk/use while charging.