How to

High quality power supplies are essential in the R&D and production lines of electrical and electronic manufacturing companies. Frequency converter is a device to transform a certain frequency (e.g. 50Hz, 60Hz) & voltage AC power into another voltage and frequency power supply, to simulate any power system standards in the world. It's a common device being used for various industries, laboratories and export-oriented electronic manufacturing companies. Calibration is essential for fre ...

The most common method used by manufacturers is to anneal the electrical steel after the lamination has been punched to its final shape (e.g. the diameters are fixed, the slot geometry is complete, and any "retaining" geometry is complete). Due to the temperatures involved (750 C or so), it is something that is done at the end of the process whereby the lamination is created - well before any actual construction (e.g. stacking) of the stator or rotor begins.

Generally speaking, the ...

Three phase asynchronous AC motor is widely used in industrial and agricultural production due to its simple structure, low cost, easy maintenance and easy operation. 3-phase AC motor uses 3 phase power supply (3 ph 220v, 380v, 400v, 415v, 480v etc.), but in some actual applications, we have single phase power supplies only (1 ph 110v, 220v, 230v, 240v etc.), especially in household appliances. In the case to run the three phase machines on single phase power supplies, there are 3 ways to do ...

To cope with the effect of the power electronics and the pulse thereof, it is usual to wind stator with specially varnished wire from supplier. This is often referred as triple coated as opposed to double coated (Standard offering). Don't be confused by number of coatings terminology. The wire has multiple coats applied. The term double and triple are generic to the industry. In effect the number of pin holes per m length of wire is reduced and the insulation (Enamel coating) on the wire has ...

There are two things to consider when looking at increasing the shaft speed of a motor (by whatever method).

First: mechanical. Can integrity of rotor design be maintained? (Typical max safe speed is NP * 1.25 which does NOT mean it operate at that speed, but only that it will not come apart and cause injury.) Will bearing and/or lubrication handle the increased speed? (There's going to be more heat.) How about vibration? (Typically, faster speeds require smoother operation to prev ...

Step 1: Determine the resistivity per unit length for the material of the conductor (you will probably have to look this up on a table of some sort - if you are using some type of cable instead of bus, chances are good the cable manufacturer has a good number to use somewhere on their website.)

Step 2: Convert the actual length of your conductor run to the same units as the resistivity measurement and multiply to obtain the actual resistance.
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The rule of thumb is less than the rated voltage or the maximum capacity of the test equipment.

There are several test techniques available in literature and standards (IEEE400). All these tests have advantages and disadvantages. Sometimes the client or the utility may have specific test requirements. However selection of tests must generally be done with the following requirements in mind:

  1. If it's a new installation, is it safe t ...

Low Voltage (400V-440V) Earthing
This discussion applies to the low voltage side of a (6.5/.400 or 11/.400 or 33/.400 kV transformers). Since your neutral is solidly grounded, the earth fault level will be sufficiently high, to trip the over current (50/51) elements. You will not need any earth fault protection. If you are running long low (really long) voltage cables you may need to provide earth fault protection.

We never design low voltage systems where the ...

The 3rd harmonic currents are not in phase with each other, they are just at 150 Hz but still 120 degrees apart relative to their period now being 6.67 ms instead of 20 ms - i.e. the zero crossings on each phase now occur every 3.33 ms instead of every 10 ms and are spread apart as a normal 3-phase set of waveforms.

But that does not mean that the A phase @ 150 Hz is in phase with the B phase and in phase with the C phase.

Remember what a delta is doing - we generally re ...

There are three ways to explain Percentage Impedance:
1) It is the % voltage drop in secondary no load voltage when a rated full load zero power factor lagging current is taken from secondary. It is the price one has to pay for transferring the current from primary to secondary side. Higher the % impedance, higher the secondary voltage drop during loading. This drop (or rise with leading loads) depends on the X/R ratio of transformer and PF of the load. % voltage drop= % ...

In long distance driving, it's helpless when our phones or laptops run out of batteries while there is only ordinary charger on hand. Most cars don't equip with AC 110v/220v power supply. In such case, a power inverter works with the car will absolutely keep such awkwardness away from you, a car power inverter will convert 12v DC to ordinary 110v (or 120v, 220v, 230v, 240v) AC to feed regular power source to small household appliances. But, there are lots of things we need to pay attention wh ...

The application of capacitors generally falls in one of two categories - correction of power factor and correction of low voltage. The power factor correction aspect has been addressed above. The impact of the capacitors on voltage level is directly proportional to its kVar rating and the inductive reactance of the circuit. This is related by the following formula:

Percentage voltage rise = (kvar)(X)(l)÷((10)(kV)²)

where kvar = 3Ø kilovars
X = re ...

If the generation side of the point-of-common-coupling (PCC) is essentially an islanded setup consisting of a few specific generators, then the amount of harmonics resulting from the generation "source" can be readily identified in a mathematical fashion from the relative impedance on the generation side of the PCC compared to the combined impedance on the load side of the PCC. (The source of such harmonics is related to both the rotor geometry and the stator winding geometry of the rotating ...

That's a reasonable, practical way to measure the approximate inductance. A couple of things to keep in mind:

(1) You're actually measuring the impedance magnitude, which will include both the resistive and inductive components of the impedance (but the resistive component is probably small compared with the inductive component);

(2) Assuming you're using true-RMS meters to measure both the current and the voltage, your estimate of the impedance will be affected by the h ...

Do we have to select a transformer (transformer loaded only by an asynchronous motor) based on the apparent power of the asynchronous motor during startup or based on the apparent power of the asynchronous motor during normal operation?

In other words, does the apparent power of the secondary windings of the transformer need to be larger than or equal to the apparent power of the asynchronous motor during startup or does it need to be larger than or equal to the apparent power of t ...

Current variations in the power supply causes severe problems in the electrical devices i.e if it increases or decreases in both cases it causes overheating which melts the conductors. High current is said when the current is above the ratings of any electrical devices, this rises the temperature of the transformer similarly when the current is below the min. rated value of the transformer but the load remains constant because of which it draws heavy amount of current to meet the load current ...

Allowable current density is not a random choice. It is directly related to the temperature of the conductor and is dependent on the insulation (on the individual strand, on the turn, and on the completed coil), the method and efficiency of the cooling, the heat transfer properties of the surrounding magnetic materials, and the nature of the current itself (AC or DC).

As a really rough approximation, a current density of 3000 ampere / mm^2 equates to something like a temperature ri ...

The purpose of a generator set is to transform the energy in the fuel used by the prime mover into electrical energy at the generator terminals. Since nothing is perfect, the amount of energy input is ALWAYS greater than the amount of energy output, resulting in an efficiency that is ALWAYS less than 100 percent.

Every fuel has a basic "heat value": this is usually broken down into two cases. The first case uses a LOW value that corresponds to the assumption where the water vapor c ...

If there is no name plate, you won't be able to know the rated voltage too. In that case, you may have to guess the approx. HP depending upon the size of the motor, select appropriate auto transformer and then run at no load by slowly increasing the voltage till it reaches steady state. I am however still not sure if this will give you the correct rated voltage. There are standard ratings of three-phase 380V, 415V & 440V. I do not know if differentiation between these is possible, because ...

If you choose a NEMA contactor, you choose a size greater than the full load amps FLA. You must derate if you have frequent starts, or jogging duty.

If you choose an IEC contactor, you need to consult the tables on expected life when you size based on FLA.

Now you need to select what type of overload relay you want. Bi-metallic or electronic, manual or automatic reset? Choose the rating based on the directions for what you choose.

If you are placing the cir ...