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It is clear by now if a power factor correction capacitor (a capacitance) is connected across the terminals of an induction motor the power factor looking from the source side improves.

Let's consider an example of a 100 HP motor. The incoming KW is about 80 KW and the power factor is about 0.85 for a 4 pole motor. Slower speed motors have more iron, they are in larger frames, therefore require more magnetizing current. Thi ...

I had an oil filled motor start capacitor blow once. What I think happened was when someone replaced it, rather than putting it back in its holder, they duct taped it to the side of the squirrel cage motor that it was starting. They started the motor up and walked away. The motor was a continuous duty motor so it wasn't turned off for a long time. One day, someone shut it off to do some servicing. They notice ...

Anything that changes the voltage (or current) waveform from a pure single-frequency sinusoid (in the case of AC) or a pure "flat line" (in the case of DC) is considered to be harmonic distortion.

In actual fact, there are transient conditions - events measured in the 0.001 to 0.05 second range - which cause such distortions very frequently (typically on the order of several times a second), even around the home. Such instances can be caused by switching (physically closing or open ...

A circuit breaker is not just a switching device - its primary function is protection, its secondary function is switching / isolation.

The fuse may be on the source side of the circuit breaker to protect the circuit breaker from the pole mount transformer PSCC (prospective short circuit current) if it is higher than the circuit breaker PSCC rating. The fuse will act as the overall system protector, should excessive short circuit current flow due to system very low impedance to the ...

In very general terms the silicon-iron magnetic cores of motors, generators, and transformers get smaller as the frequency they operate at gets higher. This of course assuming the energy delivered at the output of both cases is the same. Because of this, when you have 50 Hz core in a motor, generator or transformer, this core will generally bigger and heavier (more silicon-iron). This is because it needs to have more magnetic mass in order to be able to accommodate the extra volume of magneti ...

An isolation transformer is a transformer used to transfer electrical power from a source of alternating current (AC) power to some equipment or device while isolating the powered device from the power source, usually for safety reasons.

What this means in reality is that a normal application for an isolation transformer is to either keep the load from generating harmful harmonics back onto the distribution bus ...

There are three main losses in an un-gapped cores:

Copper loss. In low frequency, pretty much follows DC resistance, at higher frequency skin effect and proximity effect complicate resistance calculations.

Hysteresis, with goes up with gauss.

A bigger core or more turns reduce gauss, thus hysteresis loss. But, those increase copper loss. You can also use better core material, that has less loss at the gauss you are operating a ...

A three-phase network is, indeed, either grounded or ungrounded. What that means, to my understanding, is that, simply speaking, the neutral point on a wye connection can be either grounded or not. What I really mean when I say "ungrounded" is the situation when there's no closed zero-sequence path for current to flow. A delta-wye grounded transformer is commonly referred to as a grounding bank, because the delta side of the transformer can be left un-terminated--still connected in delta but ...

Some common reasons are :
1). Load applied to generator exceeds capacity, typically would cause machine to slow down, drop frequency and voltage typically cause exhaust black stacking and depending on the overload and protection settings could cause machine to stall.

2). AVR Voltage gain set too low to respond to load being applied.

3). If AVR feedback is from generator bus VT and voltage dips too far, all excitation could be lost and would typically result in an u ...

The earliest proponent of alternating current (AC), Thomas Edison pushed direct current. If I remember my history right, 60Hz was a frequency that would produce no visible lamp flicker. There were (and still remain) 25Hz, 50Hz, 133Hz, & 400Hz power systems.

The initial investment in one frequency, early power generators (hydro i.e. low frequency) would have made sudden changes to be very costly. But some of the reasons are to do with li ...

The wind speed should be mainly from 5 to 20 m/sec because this range permits the wind turbine to operation. Outside this interval, the wind turbine does not operate. It is also necessary to have historical data relevant to the wind speed for 20 years back. These data are available in certain meteorological web site or you can find measures of a site close to the airport and doing approximations to have suitable values corresponding to the site where it is proposed to install the wind farm. < ...

They were on two different subjects.
(1) Regarding unbalance in winding resistance - If the resistance that if the unbalance in phase resistance is more than 2% the motor has to be rewound.
However, this answer was given assuming the motor is wire wound. However, if it is a motor with formed coils, there exists a possibility that the motor could be partially repaired by detecting the defective coil and repairing/replacing the defective coil.

(2) The other part of the d ...

There are Three (3) methods of Powering an AVR (Automatic Voltage Regulation) or AVC (Automatic Voltage Control).

There is the PMG (Permanent Magnet Generator) which others have mentioned and hopefully made it clear that this is an independent AC generator on the same rotating shaft, so its output voltage is proportional to the speed of the Generator rotation. So should be independent of almost anything else.
"With PMG excitation, a permanent magnet generator ...

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 ...

Recently tried to drive an IE3 15kW induction motor via a soft start. Although current rating is 29.5 amps for continuous running, the inrush for these high efficiency motors is much higher than that of lower efficiency motors. Motor stalled on first attempt, then tripped breaker. Ok - easy to think this was an overload as it was from a 32 amp mains breaker. Upon checking windings it could be seen that U1-U2, V1-V2 and W1 to W2 were all balanced at 0.1 ohms. Yes 0.1 ohms. Not exactly the resi ...

Overcurrent protects the wire, overload protects the motor.
Over load and over current protection is simple....and sometimes not. For me it is easy to think of it this way. The overload protects the motor, the overcurrent protects the wire. Because the time/current curves are very far apart from each other, don't ever think that one will adequately protect for the other.

Many electricians size the wire from the starter to the motor based on the ampacity of the overload protec ...

Electrical machines designed for 50Hz can usually work safely in 60Hz power supply, but not applicable to 60Hz machines to be run in 50Hz power supply. This is because impedance of 50Hz machines increases if operate in 60Hz supply which also lowers the running ampere, while if 60Hz machine run in 50Hz power system will experience increase in running ampere & overheating that will result to reduced life expectancy of the equipment. In motors coupled to water pumps or compressors increase o ...

There's not much to see physically, but electromagnetically there's a lot going on. Once the rotor containing the field winding is up to near synchronous speed, the field is energized creating a variable strength electromagnet. This electromagnet is known as the field and is rotating inside (conceptually) three coils of wire spaced 120 degrees apart. As the magnetic poles pass by the each coil voltages that are 120 degrees apart are induced, this is known as the open circuit voltage of the ge ...

Many general contractors in many states here in the US were using aluminum wiring in housing and commercial structure construction in the 1970's, possibly later, maybe a bit earlier. I'm not sure if it's still the practice, but I hope not. There are problems with it, some of them realized after fires occurred. Wall plug sockets in the US use plated screw connections and/or compression/latching connections. The 'hot' lead connecting screw terminal is generally brass plated, and as such typical ...

I have thought long and hard about grounding. This seems to be a topic which mystifies even many electrical engineers.

Let's pretend we have a 1,000 Volt DC source. Say the negative terminal is not connected to anything but we connect the positive terminal to a copper rod and bury it in the earth. All of a sudden, when we close the switch between the battery and the copper rod, charge will be allowed to diffuse from the positive terminal into the earth. The charge will continue to ...