Industrial Electricity and Electronics

It is protection installed to protect, usually motors, from going beyond the amperage capacities that were set down by the manufacturer's specifications of the motor. As a motor loads up to its rated HP it will operate within the motors amperage range. More loading on the motor will increase the amperage draw to a point where the motor's winding will start to burn or short out due to insulation breakdown of the motor coils. Over load protection is a settable device that will limit the current to a specific value. The setting on the over current device is the motor's FLA (full load amps). If the motor amperage goes higher that the set point the overload protection, the overload protection contacts will open and drop the motor's magnetic contactor off line. In some cases this could be an annoyance but it does save the motor from destroying itself.

To measure high voltage use suitable instrument transformer (potential transformer)

Very carefully. It can kill you. The higher the voltage the more the danger or arcing over even when two conductors are not touching. Voltage meters are rated and the rating should not be exceeded. Depending on the voltage you will need the proper meter and a high voltage probe rated for the voltage you are measuring. If you don't know what you are doing, don't mess with high voltage. Leave to the pros.

A forward reverse star delta is a two in one motor starter where a motor first runs on star connection and then changed to delta connection after a time which has been set. The motor direction can be changed, whether forward or reverse

It depends on the motor. You need to look at the specifications of the particular motor. In general, if there are only three conductors, not counting earth, then it is delta; if there are four, then it is star; if there are six, then it is star-delta and you need a star-delta starter.

Using various mathematical formulas such as a 45 degree offset would be 1.4142Then there is 90 DEG, 60 Deg, 45 Deg, 22.5 Deg 11 1/4 DEG1/4 bend 1/8 Bend 1/16 Bend 1/32 Bend and then once yo know the angle you want then do the math

It is not advisable to do so. You may burn the winding, insulation may fail.

If you mean 220 single phase as in two hots and a neutral 110V-0-110V (in the US this would be 240V 120V-0-120V), then the answer is most 3-phase meters cannot be used. A few meters can be setup for either configuration, check the manual for the specific one you want to use. If you mean 220V single phase with just one hot wire and a neutral, then a larger percentage of 3-phase meters can be used, and will meter accurately. But again, the meter has have this as one of the setup choices. Check the manual. One possibility would be if you have a meter that can be setup to use 3 CT's and tell it that it is hooked to a wye system with neutral. If it sees current on just one phase to neutral, this is a valid condition, since the system could be feeding unbalanced loads (remember the meter thinks this is a 3-phase system). This would only work if the meters wiring diagram calls for CT's on all 3 phases. Many meters call for only two CT's, calculating the 3rd leg by using the two known values. This type of setup would not meter accurately for your single phase, I believe. And this will not work on a 110V-0-110V system, because a 3-phase meter expects 120 degrees between phases, not 180. Oh, I didn't mention the case where you might have two hots and no neutral. The 3-phase meter would have to be set up for a delta connection as far as the meter was concerned, since there is no neutral. It could work, not sure on this one.

The lowest amperage range on the VOM should be used to measure milliamps. To get a very accurate reading a digital VOM should be used as an analogue VOM usually loads the line that it is reading.

It is important to keep the phase sequence the same throughout the system but it is more important to connect the transformers up with the right polarities. Never close a delta connection without a test fuse wire first, for correct transformer polarity connection.

That requires some detective work.

If you know where it is in a circuit, you might be able to figure out its function by context (seeing what it's connected to and what it might do).

You might be able to figure out the manufacturer by looking at subtle details of the package size and shape.

If you have the equipment, there are ways to disassemble and reverse engineer the chip and see the circuitry through a microscope to figure out its internal schematic.

Power factor is the real power (watts) divided by apparent power (the vector sum of real and reactive power). Reactive elements (things that have inductance or capacitance) cause phase shifts between voltage applied to them and current passing through them. This phase shift is a result of these elements holding power, then releasing it. Since these elements are not actually using power, this does not show up on your electric bill (unless you are billed on VARs as well as watts). Although they don't use real power, these reactive elements do cause "extra" current to flow, which the power company must supply. If this current is excessive (so you have a very low power factor) the power company must install oversized equipment to meet your demand; this means an added expense for them, with no payback on your electric bill. This is why power companies will often require a certain power factor be met, or bill you extra per kWh of use.

Note power factor is a result of the load, not the other way around (a better question might be what is the a load's effect on power factor).

Most times it is the surge current the breaker can withstand in kilo-amps. A normal breaker will see several thousand amps in a short condition. The breaker must be able to withstand and break that current safely.

It is apples and oranges--kVA and volts are different units describing different things. Determining kVA requires measuring both voltage and current.

my nalgas

For Single Phase,

P = VI cos (theta)

therefore cos(theta) = P/VI

here

P = Power

V = voltage

I = current

theta = phase angle current to voltage

cos(theta) = power factor

For Three Phase,

P = 3VI cos(theta)

where V = phase voltage and I = phase current and theta = phase angle

Stator is part of rotating mechanical device thats sorrounds the rotor to rotate it through the induced magnetic field while the Rotor, is the one who is rotated by produced magnetic field in the stator,.

It's a "quad, 2 input nor gate".

To understand the significance of a "nor" gate, you need to understand a little about digital logic.

An "or" gate takes 2 or more digital inputs and if either is "on", the output will be on. (asserted high).

A "nor" gate inverts the output of the "or" gate, meaning that when either of the outputs are "on", the output will be "off" (asserted low).

The two input part of the description just indicates that it only accepts two inputs.

So, simply stated:

If either (or both) input(s) of a quad, 2 input nor gate is (are) asserted high, the output will be low. If both inputs are off (low), the output will be high.

On the whole megger testing is non destructive. What happens is a DC voltage is applied to the device or winding under test. It is an insulation test to see is the insulation has been injured in any way to cause a short circuit when normal power is applied to it. On my megger there are 3 ranges 300V, 750V, and 1000 volts. Applying the proper voltage is essential to not damaging the device you are testing. Working voltages up to 240 volts should use the 300 range. Working voltages up to 600 volts use the 750 volt range and working voltages above 600 use the 1000 volt range. As you can see if you used the 1000 volt range on a device that had a working voltage of say 24 volts you could damage the insulation just by testing it. So meggering a device is non destructive if you use the tester as its instructions tell you to. To megger a cable connect one lead to the ground or outside sheath of the cable and the other to the inside wires one at a time. Test each wire separately. Then for a wire to wire test connect the meter across two of the conductors and test. For a three wire cable, test 1 to 2, 2 to 3, and then 3 to 1.

As well as motors, contactors also have kW and Ampere ratings. Have a look on the name plate of your motor and you will see its maximum current draw (amps). Select a contactor with a current rating greater than this.

Switching any two of the three phases will cause the motor to turn in the opposite direction. This rotation change should be done in the motor's junction box so that the colour phasing will remain accurate throughout the circuits system. For that reason, motors used where the direction of travel matters (like for elevators or escalators) are equipped with reverse phase relay devices that prevent the motor from operating unless the phases are wired in the correct order.

Switch two leads of the wires going to the motor for ex. L1,L2,L3 change to L1,L3,L2.

If this motor is wired for wye-delta starting, it will be easier to change the incoming power than at the motor junction box. Wye delta motors are six lead or twelve lead motors and lead pairing is critical on a wye delta setup. If the motor is started across the line like a standard nine lead motor, then by all means change it at the motor junction box.

0.2S is more accurate at low currents than 0.2. While both have maximum errors of +/- 0.2% at 100% and 120% of rted current, 0.2S has +/- 0.75% at 1%, 0.35% at 5% and 0.2% at 20 % of rated current while 0.2 has 0.75% at 5% and 0.35% at 20% rated current. These values are found in IEC Standard 60044, Tables 11 and 12.

Any where that a three phase supply distribution is needed to operate three phase equipment.

compensating winding is used for equal load sharing of two generators running in parallel. while interpole winding is used to minimise the effect of armature reaction by supporting the main field.