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Both are short circuits. A short circuit is an unintended connection between phases or between on or more phases and earth. The scenario with a connection from one phase to earth is typical what we name an earth fault. An earth fault can occur if you have a 3 phase system in underground cables with 1 phase per cable. If one cable is digged into accidentally you would get an earth fault. Could also be a 3ph system in overhead lines with a tree getting too close to one phase. This would be an e ...

The frequency output of the Permanent Magnet Generator is related to the pole count of the exciter - compared to the motor it is feeding.

If the motor line frequency is 50 Hz, then the exciter has 3x the pole count of the synchronous machine (i.e. 2-pole synch with 6-pole exciter design, or 4-pole synch and 12-pole exciter, etc.)

If the motor line frequency is 60 Hz, the exciter has 2.5x the pole count of the synchronous machine (i.e ...

I have changed the existing winding with a different winding scheme. I have also changed the shaft of the rotor and bearing. Original shaft has been replaced with a new longer shaft and accordingly supported by a different bearing at the end of the shaft. Two touchdown bearing has also been used near the end plate to protect the winding. The question is that I know natural frequency of the rotor and if we bypass that frequency quickly then we can achieve higher speed. So what are the constrai ...

Consider that a stand-alone machine with a PLC: you are in control of what and what is not common grounded on most PLCs by the way you wire it. Often times there is a jumper you can removed so that you can force the common ground point to be that desired central point in your main panel. Now throw a PC into it; if your IT group mandates what PC is used (instead of being able to choose an industrial PC for this and other merits) you suddenly are not in control of the ground point! Most commerc ...

For starters, it is very uncommon to come across cable that has no marking at all, and I would be very careful when using such cable for any electrical installation, since you can not be certain of what temperature range and voltage level it can be good for, in addition to the question of cross-section area. It could even be that the manufacturer has detected some manufacturing flaws, and therefore decided not to mark it, and simply sell it to a scrap metal dealer instead of bringing it to th ...

Most modern day variable frequency drives (VFD) will offer V/Hz control, sensorless Vector control and optionally closed loop control for full field orientation control method. The V/Hz control is retained for applications generally whereby a high torque speed or dynamic control is not required such as applications like centrifugal pumps and fans, or lightly loaded applications.

Although it can be argued that in modern Sensorless Vector VFDs the motor modeling and speed of the M ...

The core saturation is a physical phenomenon. It happens when the coupled magnetic flux is so intense that all magnetic domains on a ferromagnetic material are already aligned and thus does not respond to any further increase in the flux. The implications on the current transformer secondary current may be diverse. Having a saturated core does not mean the current on the current transformer secondary will be high or even constant as the flux increases.

Once saturated, the inductan ...

Sinusoidal and trapezoidal control references the method of commutating the BLDC motor. The BLDC motor can be pictured as a 3 cylinder engine with a hard crankshaft between them. To make the Engine move you fire your spark plug at the top of the cylinder to ignite the fuel and push the engine down and rotate the shaft. The timing between each cylinder is 120 deg apart because the cylinders are hard shafted. Now imagine that the BLDC motor is that Engine. the Use of hall effects tell you when ...

The rotating speed of the stand was nowhere near enough, so we made an emergency plan with a Variable Speed Drive on the original (4 pole) motor - up to about 200 Hz. This was still not fast enough (we reached the constant power flux limit) so we procured a new 2 pole (22 kW) motor.

I must emphasize that this was an absolutely standard off-the-shelf (Chinese manufacture actually) motor from our sister company who supplies these motors. There was absolutely nothing special about it ...

My choice is not only a shunt-wound motor, but a straight-shunt-wound motor. With the advent of SCR-based DC drive controllers, the need for specific motors has diminished. Especially in the case of a compound-wound, or a stabilized-straight-shunt-wound motor, the addition of a series field was an attempt to keep the motor under stable control during extended-speed operation, where the shunt field is weakened to attain speeds beyond base speed. They're also somewhat useful is containing armat ...

Every motor driven application needs to be evaluated and the starting and control method properly chosen to meet those needs. If variable speed is not required for the process and the power and mechanical systems are robust the direct-on-line (DOL) starting may be the best choice. If the power system and / or the mechanical system are weak and only fixed speed is required for the process then a reduced voltage starter with bypass may be the best choice as long as the reduced starting torque t ...

Synchronizing module ensures that voltage, frequency and phase angle difference between the two systems is within acceptable limits relative to one another. Since the upstream source of two identical transformers is a common bus, so synchronizing module is not required (provided tap position of transformer is same). As load transfer is to be done without any interruption, so momentary paralleling is required. When planned outage of one of the transformer is required, the respective incomers s ...

Using a line choke (inductor) that was designed for 50 Hertz on a 60 Hertz power system would appear to be an error/omission on the part of the designer/engineer but it can work satisfactorily if it is applied correctly and operated within its ratings: volts/hertz, voltage, current, harmonics, volt-second balance, temperature, etc.

The high levels of noise can be due to many factors. The most likely are harmonic currents produced by the d ...

1) Brownian motion - this is motion due to heat. Remember, electrons tend to be bounded to atoms, but as you increase the heat, the electrons may leave an atom and travel freely, but this motion will be random and though a single electrons move, the sum of all electrons motion is essentially zero. This motion is a source of electrical noise, a small random current that exists in most everything.

2) Motion in response to an electric field - applying an electric field will place a fo ...

Reputable manufacturers are required to design the mechanical system of an induction motor (or generator) to be mechanically safe at a minimum of 25 percent above listed nameplate maximum speed. In some specific instances, a user may have defined something even higher, but the chance of this is vanishingly small.

What "mechanically safe" means is that the rotating components of the machine will not "break" under the higher centrifugal / centripetal loading resulting from the highe ...

It basically depends on weather and intensity of radiations, the peak efficiency of a solar panel determine by the surface area of the panel by multiplying the length with width and the surface area is aperture area of the solar panel, therefore the measurement does include the frame. Then find the name plate rating of the panel from the datasheet, the name plate rating at STC (Standard Test Conditions).

This is the standard used to determine how many watts of power are produced i ...

It's useful to warn engineers against taking decisions without any supporting facts and numbers, just taking for granted what salesmen say. When just connected to the grid, an induction motor will probably have more than necessary flux, because it will probably work below its nominal power. The assumption that one can exactly match the size of the motor to the application is unrealistic. The motor cannot be sized for exactly the required torque for many reasons, including the fact that sizes ...

For swimming pools most people are hurt when they touch something that is grounded i.e. hand rail or some other metal object (Our body is a better conductor than fresh water). Your body does not feel voltage by itself you have to create a path to ground.

The reason people are more at risk of electrocution in fresh water is because the water decreases the skin contact resistance, which is by far the highest resistance in the circuit when a human body is electrocuted. As such - in fr ...

Many consider the "ground" of the building to be impeccable "earth ground". I have only found one building with a perfect earth ground. That plant used a 300 foot well with all metal piping, and a meticulously bonded water sprinkler system. They used this system to ground all their systems to. This was the only plant that I never had any noise problems with.

Back then, I was supporting a PLC control system with PC and instrumentation. Looking back, I think the system design was in ...

If the motor is designed to run in star a 380V 3-phase power supply, then it cannot be connected in delta on the 'same' supply. That would be the equivalent of applying 380 volt to 220v windings so clearly the motor would fail.

Note that in star, each winding gets root3 of the applied voltage (or 380/1.732) connecting in delta means that each winding get the phase-phase voltage EG 380V.

If the motor is rated at 380V - 'delta connected' then it could be connected in sta ...