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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 ...

Assume that interconnect two separate systems by closing a circuit breaker on a tie-line. The voltages at both ends of the breaker are independent of each other, as each voltage "belongs" to one system, each system still operating isolated from the other. So, if the voltage difference across the breaker is sufficiently large (and remember that this is a phasor voltage difference, magnitude and phase) when the breaker is closed, that will be equivalent to a fault, a short-circuit in the grid. ...

In this pursuit, I would like to begin with the understanding of the different word "TRIP or RELEASE", which is in fact a combined "ELECTROMECHANICAL MODULE or MECHANISM that comprises of a "mechanical latch" and a "Electrical Relay / Release" which can OPEN THE SWITCHING DEVICE e.g. a circuit breaker, by electrical "energisation" or "de-energisation", according to their characteristics.

Now coming back to o ...

The circuit breaker analyzer will perform 3 of more specific tests.
They are the a. Timing measurement, b. Motion Measurement, c. Coil Current Measurement.

For a. The CLOSE/OPEN and multiple CLOSE-OPEN option will give you the precise trip/close timing also the reliability of your circuit breaker in effect to corrosion effects.

For b. Where you can connect analog/digital transducers to the an ...

Why not a 59 Hz? I prefer a prime number. If I were J.P. Morgan, I'd like to make Tesla have such a cool frequency. Or US yields to 55 Hz, and Germany get a 5 Hz bonus.
In the true world, a wide range of frequency for electrical machine could work economically, but in a real world, people make the standard, and 60 Hz simplified, e.g. the calculation. I guess Nikola Tesla had more common sense than I have. However, if I were born 100 years earlie ...

Generally two factors will melt and damage the cable insulation:
1- Overheating due to excess current;
2- Insulation breakdown due to over voltage or voltage surges.

In the case of excitation system it should be noted that during field forcing the excitation current will exceed the nominal current, therefore you should review your system document to find the maximum current during field forcing or other current demand of the excitation system during the operation as for co ...

Required precision, wire length and amount of electrical noise within the system are all considerations. There are also various levels of isolation i.e. some analog I/Os have a locally generated power supply which may or may not be isolated from general logic power or may use a separately provided supply;
Similarly, the digital signaling portion may or may not be isolated from the control bus o ...

To answer your first question, regenerative braking in variable frequency drives (VFD), the premise is that whenever a motor is rotating faster than the winding are excited the motor becomes a generator. Regenerative braking means the voltage produced is "placed somewhere else". Often the excess voltage can be absorbed by the IGBTs or the addition of a braking resistor...maybe even placed back on the AC power network. I ...

Q: Has anyone got experience in using a 50 Hz Alternator of about 20 MW, in a 60 Hz system country? What are the changes required in the alternator? Is it economical to carry out this change or one has to go in for a new alternator for 60 Hz only. There are lots of commercial requests for such usages of 50 Hz machine in 60 Hz locations and vice versa.

A: You can use a 50 Hz alternator in 60 Hz power system without changing the internals. The concern though, is the operational speed ...

It is important to recognize different time frames for the expected responses from individual generation units and from the power control center regarding balancing generation and load. The key variable here is the system frequency. If the frequency is below synchronous, you have too much demand for the available generation while frequency above synchronous indicates more generation than demand.

In the example of the outage of a 600 MW generator, frequency will initially drop at a ...

If BOTH bearings are not properly insulated, operating on the variable frequency drive (VFD) will cause bearing damage. This is even more pronounced with bearings that take axial thrust loads, since there's now another contact surface in addition to the "normal" radial loading. Note that the damage MAY appear on the housing, rather than the bearing - it all depends on how the energy dissipates within the bearing region.

True, some of your observed temperature rise may be a result o ...

Induction motor with squirrel cage rotor has two different speeds. The synchronous speed refers to the stator rotating magnetic field, which depends on the number of poles and frequency. The other speed is the rotor's. The rotor speed will be always slower than the stator speed, we call it slip. Without the slip, the squirrel cage induction motor doesn't have torque. Even without load the motor has slip. It increases with the load, according to the current x torque curves you can check it out ...

I have an interesting (yet frustrating) project I am trying to get to function accurately. My customer is a machine tool shop that refurbishes well casing for oil and water drilling. We installed a VFD driven system to move the pipes from area to area. The reason for the VFD is for the high torque start and stop and also the fact that not all the pipes are the same size and weight. The problem I am trying to overcome is when they are driven into the CNC lathes that clean up the threads on the ...

I have used three different Methods depending on the details of a specific project plus I do not use the Method 4.

Method 1. Secondary pre-charge
This is normally the most economical Method. It uses a small pre-charge transformer to apply a voltage to the transformer's secondary and I normally use 90% of the rated transformer's secondary voltage. The required current is approximately the transformer's magnetizing current. A typical value is 0.5% of the rated w ...

The use of (power in watt) = (volt) * (ampere) works great to determine the electrical power requirements. However, it neglects the fact that every system has some amount of loss when energy is transformed from one state to another.

If you're really monitoring a 169 ampere current draw for a machine rated 60 kW at 400 V, then you have one of three conditions:
A) The motor efficiency is extremely low (roughly 88 percent). Note this value SHOULD be in the 93-95 ...

All electrical machines have some amount of dis-symmetry to them, just because they are constructed of individual parts. Sometimes this is in the steel portions (segmental laminations, or unequal airgaps, etc) and sometimes in the winding (unequal resistance paths, different connections and/or lead lengths, lead routing, etc).

As soon as there is a difference in the magnetic path (or the magnetic strength), some amount of voltage will be induced on the motor shaft. The purpose of a ...

Herewith some information relating to Tan Delta (Power Factor) and Capacitance Test on transformers from our perspective. With regards to your statement relating to whether Tan Delta testing could have any adverse effect on transformer health, the following:

- This test is a diagnostic insulation assessment tool that is a measurement of the fundamental AC electrical characteristics of insulation. These electrical characteristics could provide an indication of moisture, insulation d ...

I have a question regarding protecting a variable frequency drive (VFD). I have read that the important part to protect of the variable frequency drive is the active front end (prior to the IGBT's). I also am under the impression that the VFDs themselves protect the motors from faults. So my questions are as follows:

1. Do you need an overload to protect the motor? And if so do you put in on the PWM output side?
2. How should I protect the variable frequency drive and Motor? ...

1. Explain why the efficiency of the induction motor increases when the mechanical load increases.
2. Explain why the input power factor of the induction motor increases when the mechanical load increases.

Explain:
1. The efficiency of the induction increases when the mechanical load increases because as the motors load increases, its slip increases, and the rotor speed falls. Since the rotor speed is slower, there is more relative motion between the rotor and the stator ...

Q: What will happen if shaft earthing brushes are not provided for VFD driven motor? Is it acceptable? Motor is of 50 hp, 415 V, and is at 200 m from VFD panel.

A: More than likely it will work just fine. Think of the shaft brushes as cheap insurance. They will make sure the bearings are protected from discharge current to equipment ground. On the other hand, the brushes will also ensure a long useful life from the motor by preventing eve ...