Electrical Engineering

You can get them from EBAY

http://www.ebay.com/itm/20-GW-Good-Work-Rectifier-IN5399-Diode-RoHS-Free-/390062236202

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You can get them from ebay but you would be paying 50 cents for a 4 cents device plus shipping. which in my humble opinion is a ripoff.

Farnell still sells this device for GBR 0.03p (4 Cents).

or you could substitute it with something like the CR1-100

The fuse is rated to protect the equipment, the supply, and you. Change the fuse for a higher rating and you compromise your safety and equipment and supply safety; increasing the risk of electric shock and of fire.

DC motors use PWM (pulse width modulation), which can easily increase or decrease the power to the motor, thereby increasing or decreasing the motor speed by modulating the width of the pulse. Stepper motors have fixed frequencies, thereby having fixed motor speeds. As a result, the speed of the stepper motor cannot be controlled when the load is increased.

Auxiliary transformer- current transformer

The current transformer is working based on two theories.

1.Ampheres law.

2.Faradays law.

Amp.law- whenever a current flows through the conductor it will produce magnetic flux around the conductor.

based on above principle- current flows through the primary will induce a magnetic flux in the CT core.

Faraday law- whenever a conductor cuts the magnetic flux or magnetic flux cuts the conductor will induce a emf across the conductor

based on above principle- the magnetic flux in the core will cuts the windings. so emf is induced across the secondary terminals .

whenever the secondary terminals connected with burden will make a closed path and current flows through the secondary to burden.

It generally reads RMS value of the voltage being measured

Communication since WW2 has been enhanced by satellites, optical fibre cables, the Internet, WWW software and cheap computers.

The symbol of the ohm, i.e. the unit of resistance, is the Greek letter Omega: Ω

yes we can generator supplier in dubai. We can help you. vuralalper@hotmail.com

2 times per second x (2.5)= 5 volts

6 times per second x (2.5)=15 volts

2 pole, 3 wire.

turn the flyweel on a lath and install gear reduction..(flexplat gear) not a hard task with the right equipment

I think you are asking why is it necessary for an automobile battery to have low internal resistance. That is because the internal resistance of a battery limits the amount of current it will produce. Imagine connecting a wire from the plus side of the batter to the minus side. Then, the amount of current the battery produces is the voltage of the battery divided by its internal resistance.

So, if you take a flashlight battery and connect a wire between the two terminals, it might get a little warm. If you take a car battery cannot a wire between the two terminals, the wire will probably melt! (Don't try this!) If you take a lithium ion battery from your computer and short the two terminals, the battery will catch on fire. (Computer companies build extra resistance into the batteries to help to prevent that.

So, why do cars need low internal resistance batteries? They need lots of current to start those large gasoline engines turning. You car battery does a tremendous amount of work to start your engine (and remember, energy and work are the same in physics).

Most power transformers I have seen are filled with oil, and have a base rating of ONAN - which stands for oil natural, air natural. This is a cooling type. There are two main ways to cool a transformer above this rating - by using forced air - essentially attaching fans to help pull heat away, or using oil pumps.

With air, the next typical rating is ONAF, or if there are two different ratings (meaning some fans turn on at one, and all fans turn on at two) they may be named ONAF1 ONAF2. thiws stands for oil natural, air forced.

If oil pumps are installed, the rating will be OFnn for oil forced. It is possible to have both oil forced and air forced, or just oil forced - OFAN or OFAF. Just an FYI, in my experience oil pumps are typically avoided. It was discovered that pumping the oil can cause a static voltage buildup in the oil, which can lead to catastrophic failures; this doesn't seem to be a problem if oil pumps are not used.

under internal fault conditions , CT primary current produces steep insrease in voltage across the relay. This will exceed the burden 3kv normally designed as per. To get protected from the voltage, metrosil is connected across the relay , to drop the voltage.

You cannot use an ordinary multimeter to assess the difference between a normal power transformer winding and a shorted power transformer winding. You need a Q meter and/or to power it up at a reduced voltage with limited current to see what happens. Note that a shorted power transformer is capable of exploding, so you need to take appropriate safety precautions.

75 ohms. R = E/I.

lines that all the points on it have the same head pressure and eqipotential lines are always prependicular to the stream lines .

The use of a star delta starter is for motor control only and not resistive heating loads. This type of starter is used to dampen the inrush current by using a lower voltage to start the motor.

Usually, overcharge, sometimes overdischarge. Check the alternator - the regulator is probably shorted.

A step-up transformer needs more turns on the secondary windings than on the primary windings to increase the voltage.

The relay's coil burns open. This is not necessarily the answer. Remember normally when a DC current is used a specific magnetism with a prominent North and South is created by the current carrying coil. If we are to use this magnetism together with another permanent magnet's interaction. a deflecting force results. This deflection can be controlled by a restraining spring and the angle of deflection is often a measure of the current. Now in place of the DC current an AC current is made to pass. The deflection is not shown by the meter as ac will create poles as per its frequency and direction of current flow. Also based on the magnitude of its current is the magnitude of the strength of the coils magnet magnet. Assuming same voltage in both cases the coil need not burn out. The deflection is absent here as polarity keeps reversing several times each second and the average value of the 2 forces cancel each other. In DC this deflection is prominent as the poles remain fixed. In relays there is no permanent magnet. However the AC current fed to relay coil will have a higher impedance in comparison to a DC current. This is because of a phenomenon called self inductance. The self inductance will create a back emf that will restrict the current in the coil. Hence the magnetising of the relay core will not be strong. Hence the relay may not operate at all. In Dc this back EMF is momentary and gradually the current increases to a maximum and stays steady. Hence a DC relay if fed by an AC voltage of same magnitude may not be able to pick up and do the necessary activation.

Take the back off and look inside.

(In New Zealand) there will be a fuse associated with each electricity consumers line, and when the demand exceeds its rating, (~100A) it will pop, requiring re-wiring, in the same way as a lower current fuse on your power meter.

On an utility circuit they do not have fuses, instead they have circuit breakers. These are a device that mechanically interrupts the electrical supply. The (lower voltage) ones are used to manually isolate supply during wiring maintenance.

On high voltage supply, there is more complex automatic equipment, with special precautions taken to prevent or break any arc formed when the circuit breaks. These may have a hydraulic-powered break system to ensure a rapid break; or possibly a blast of gas across the arcs path to extinguish it.

On major circuits, the breaker may attempt to re-set up to three times, on the assumption that the 'short' is a transient one. (Birds, possums) If this assumtion proves incorrect, the breaker remains open.

In New Zealand the possum problem is real, and almost all power poles have a band of metal to deter possums climbing.

In closing, fusible links are not suitable for large currents, nor for high voltages. In melting, the fusiblelink may create a path of metal vapour which can sustain an electric arc. There are made High Rupture Current fuses, in shich the fusible link is enclosed in a volume of sand, which quenches any arc.

The arcing problem is even more severe with DC, and special tricks are employed in these cases.