Anyone help me in electrical engineering stuff ??

[mudwhistle]

"Pulse" sounds more like the hertz or frequency of the generator/alternator.

A generator/alternator will pulse + or - volts for each phase. A 6 pulse will have 2 pulses (one positive and one negative) per phase and a 12 will have 4 per second. These pulses can be multiplied by using a transformer and separate windings. Or you can use a VFD in which high AC wattage is turned into DC and then transistors pulse out positive and negative Current to simulate a sine wave.

Current and voltage is generated by the RELATIVE motion of a coil passing through a magnetic field. (Meaning actual, physical motion is not required....just an increasing and decreasing magnetic field)

This is all happening at 60 HZ or cycles per second.

 

[mudwhistle]

As a previous electronics tech, I never once used algebra, trigonometry, or calculus.

And thank God for handheld calculators.

They wouldn't let us use calculators during tests.

 

[ReinyDays]

I don't know if this has been answered ... but 3-phase is a type of AC ... our homes almost always has 2-phase AC ... and it mainly matters for electric motors ... in industrial settings with lots and lots of big fucking electric motors get better efficiency with 3-phase AC ...

This is special motors, special wiring ... even the overhead lines coming in are special 3-phase ... industrial sized motors ...

 

[JohnDB]

I don't know if this has been answered ... but 3-phase is a type of AC ... our homes almost always has 2-phase AC ... and it mainly matters for electric motors ... in industrial settings with lots and lots of big fucking electric motors get better efficiency with 3-phase AC ...

This is special motors, special wiring ... even the overhead lines coming in are special 3-phase ... industrial sized motors ...

No....
Household current is usually a single phase of a delta-delta transformer that is center tapped to ground.

In commercial 3 phase each phase is 60 degrees apart so 120 + 120 = 208 volts.

In household current....
120 + 120 = 240 volts because they are 180⁰ apart. Because they are the same phase.

 

[mudwhistle]

I don't know if this has been answered ... but 3-phase is a type of AC ... our homes almost always has 2-phase AC ... and it mainly matters for electric motors ... in industrial settings with lots and lots of big fucking electric motors get better efficiency with 3-phase AC ...

This is special motors, special wiring ... even the overhead lines coming in are special 3-phase ... industrial sized motors ...

That transformer you see on the pole outside is changing your power from 120/240. In Germany everything runs on 240 50 HZ. Here in the states our lights and receptacles run off of 120.

 

[ReinyDays]

That transformer you see on the pole outside is changing your power from 120/240. In Germany everything runs on 240 50 HZ. Here in the states our lights and receptacles run off of 120.

My transformer is strictly 13,800 VAC, and it's stepped down to 240 VAC for household use ... I have two 120 VAC "legs" and a return coming into my home, the steel cable is acting as the chassis ground ... I wasn't referring to frequency ...

JohnDB corrected me about single phase ... typically a neighborhood would have just a single high voltage wire, and the two 120 VAC legs picked off of that ... I have three high tension wires in my neighborhood, which includes a rather large milk processing plant ... so all I need is a three-phase transformer and I can fire up some cyclotrons ...

 

[The Duke]

I know who can answer this easy. toobfreak
Even though it's kinda already been answered.

 

[Moonglow]

I don't know if this has been answered ... but 3-phase is a type of AC ... our homes almost always has 2-phase AC ... and it mainly matters for electric motors ... in industrial settings with lots and lots of big fucking electric motors get better efficiency with 3-phase AC ...

This is special motors, special wiring ... even the overhead lines coming in are special 3-phase ... industrial sized motors ...

Two-phase electrical power is an old-fashioned method of distributing alternating current (AC) electricity. It was developed in the early 20th century as an improvement on single-phase power.

How it works

• Two circuits are used, with voltage phases that are 90° out of phase with each other
  
  
• Two hot wires and a neutral wire are used
  
  
• Two-phase power can provide both 120-volt and 240-volt outputs
  

Why it was used

• • Two-phase power was designed to provide a consistent supply of power to loads and to create a strong starting torque for induction motors

Why it's obsolete

• • Three-phase power is more efficient than two-phase power and has become the standard method of distributing electricity

 

[ReinyDays]

Two-phase electrical power is an old-fashioned method of distributing alternating current (AC) electricity. It was developed in the early 20th century as an improvement on single-phase power.

How it works

• Two circuits are used, with voltage phases that are 90° out of phase with each other
  
  
• Two hot wires and a neutral wire are used
  
  
• Two-phase power can provide both 120-volt and 240-volt outputs

Why it was used

• • Two-phase power was designed to provide a consistent supply of power to loads and to create a strong starting torque for induction motors

Why it's obsolete

• • Three-phase power is more efficient than two-phase power and has become the standard method of distributing electricity

This has already been corrected ... where I say 2-phase should read 1-phase ... my mistake ...

 

[JohnDB]

This has already been corrected ... where I say 2-phase should read 1-phase ... my mistake ...

Just as an FYI...
These drones which are very popular are using 3 phase motors powered by batteries.
They achieve 3 phase power with what is called a pulse bandwidth modulator. It's a bunch of transistors that cycle the electricity with pulses to mimic three phase power instead of using DC power.
Where this is helpful is that instead of having 60 cycles per second the cycles can be whatever is needed to change rotor speed. Instead of more power needed....it's just pulsed differently making the drain on batteries more consistent and ultimately lasting longer.

 

[ReinyDays]

Just as an FYI...
These drones which are very popular are using 3 phase motors powered by batteries.
They achieve 3 phase power with what is called a pulse bandwidth modulator. It's a bunch of transistors that cycle the electricity with pulses to mimic three phase power instead of using DC power.
Where this is helpful is that instead of having 60 cycles per second the cycles can be whatever is needed to change rotor speed. Instead of more power needed....it's just pulsed differently making the drain on batteries more consistent and ultimately lasting longer.

Yes ... induction motors are the best ... the main disadvantage is you're stuck at 3,600 rpm (3,000 rpm in metric) in a plant-in-place environment ... the last DC to AC converter I worked with used triode vacuum tubes, you'd think the heater power supply alone would drag the poor drone down to the ground, killing all the occupants ...

It would be cheaper than a 10,000 foot long extension cord ...

 

[JohnDB]

Yes ... induction motors are the best ... the main disadvantage is you're stuck at 3,600 rpm (3,000 rpm in metric) in a plant-in-place environment ... the last DC to AC converter I worked with used triode vacuum tubes, you'd think the heater power supply alone would drag the poor drone down to the ground, killing all the occupants ...

It would be cheaper than a 10,000 foot long extension cord ...

When the wattage needs are too high transistors won't work anymore and they still will use vacuum tube transistors. $20k + each tube....and a minimum of 3 (one per phase) but it's actually a vacuum tube. (Dunno how expensive they are anymore after this bout of inflation)

But you can still get a lot of watts through solid state PBMs .

 

[the watcher]

When they design afds (adjustable frequency devices) to control AC motor speed, they use 3phase bridge rectifier circuits with a scr (silicon controlled rectifier) to fire at variable phase angles to create variable voltage and frequency output to motors and transformers to control speed without excessive waste and heat. Each firing point is called a pulse, so I'm guessing that is what you are talking about, the trigger for the rectifiers. The more pulses per cycle the smoother the sine wave.

 

[JohnDB]

When they design afds (adjustable frequency devices) to control AC motor speed, they use 3phase bridge rectifier circuits with a scr (silicon controlled rectifier) to fire at variable phase angles to create variable voltage and frequency output to motors and transformers to control speed without excessive waste and heat. Each firing point is called a pulse, so I'm guessing that is what you are talking about, the trigger for the rectifiers. The more pulses per cycle the smoother the sine wave.

A "rectifier" is a device made out of diodes that turns AC into DC. It can be half or full wave.

Programming the pulses can create various scenarios for the motors to increase torque or speed or whatever is needed for things like startups or shutdowns or various scenarios involving torque after slowdowns.
We used to name them with odd names like "Kung fu kick start" and etc.

 

[luiza]

Anyone help me in electrical engineering stuff​

Happily .

Always remember to moisten a live wire in your mouth before connecting it .
Have a practise today and make sure you get a good dollop of spit on your tongue

 

[toobfreak]

I know who can answer this easy. toobfreak
Even though it's kinda already been answered.

Kinda stepping into this conversation in the middle of it and not sure what the discussion really is but what Reiny said sounds right and Mud is wrong.
If you see those big high pressure power lines strung across the countryside on big towers, those are the ones bring the really high voltage (usually around a half million volts) from the generation plant to local regions. This minimizes what is called the I2R losses (basically, the wires acting like resistors dropping voltage). This was the big advantage over Edison's DC system.
From there, it is dropped back down (sometimes twice) finally at your intermediate local substations to around 11kVAC or thereabouts depending. You might see one within a few miles of your house as a small building. These are the ones that would be critical and hard to replace in the event of an EMP pulse.
From there, the power is distributed out to your community streets to the little transformers you see on the telephone pole near your house.
Those usually output a split phase 220VAC to the homes.
Your furnace, electric range, dryer, etc., run off that.
The 110VAC in your wall outlets (maybe as high as 120) is simply half of that taken from the one pole to the ground at mid tap.
Of course, there are many variants depending if you are running power to heavy industry, business, or residential.

 

[JohnDB]

Kinda stepping into this conversation in the middle of it and not sure what the discussion really is but what Reiny said sounds right and Mud is wrong.
If you see those big high pressure power lines strung across the countryside on big towers, those are the ones bring the really high voltage (usually around a half million volts) from the generation plant to local regions. This minimizes what is called the I2R losses (basically, the wires acting like resistors dropping voltage). This was the big advantage over Edison's DC system.
From there, it is dropped back down (sometimes twice) finally at your intermediate local substations to around 11kVAC or thereabouts depending. You might see one within a few miles of your house as a small building. These are the ones that would be critical and hard to replace in the event of an EMP pulse.
From there, the power is distributed out to your community streets to the little transformers you see on the telephone pole near your house.
Those usually output a split phase 220VAC to the homes.
Your furnace, electric range, dryer, etc., run off that.
The 110VAC in your wall outlets (maybe as high as 120) is simply half of that taken from the one pole to the ground at mid tap.
Of course, there are many variants depending if you are running power to heavy industry, business, or residential.

110 volts is common in industrial settings due to the long distances a circuit will travel. Possibly outside of metal conduit.
CIP is that sometimes temp power is needed for something and the maintenance team runs romex or VJ cable to the spot along a steel beam. Well that steel beam can have a lot of capacitance voltage induced into it due to power being run next to it for a couple hundred feet and iffy grounding at best. The higher the voltage the more chance of capacitance and stray voltages and arcs forming.

And 10 or 12 volts dropped might increase the amps used but it really won't affect most electrical systems much. Where in a house the voltage being a bit higher tends to reduce amps and heat....which is more important in a wood framed house.

Most high voltage TRANSMISSION lines have 64kva phase to phase anymore. The 500 KVA phase to phase has been done away with. That 10 foot minimum clearance was getting to be too difficult to keep in switchyards. (Which are in cities)

DISTRIBUTION lines of course don't need anywhere near that sort of voltage (except in an industrial plant). So most of them have 11.8 k volts per phase.

 

[toobfreak]

110 volts is common in industrial settings due to the long distances a circuit will travel.

Years ago I built an LED bar graph voltmeter that I kept plugged in near my home theater just to monitor voltages. The voltage varies all over depending on load and location, from as low as maybe 105VAC to as high as maybe 130, but usually in the 110, 115, to 120-125 range. Stuff tends to work better the higher the voltage.

But the voltage isn't too critical, what is critical is the frequency. The 60Hz frequency must be critically maintained by the grid for various reasons and if you put a frequency counter on your AC, you will usually see the frequency as 60.00 Hz, to maybe briefly as 59.99 to 60.01Hz, and even at that, this might simply be random counter error in the circuit and not even the line.

 

[JohnDB]

Years ago I built an LED bar graph voltmeter that I kept plugged in near my home theater just to monitor voltages. The voltage varies all over depending on load and location, from as low as maybe 105VAC to as high as maybe 130, but usually in the 110, 115, to 120-125 range. Stuff tends to work better the higher the voltage.

But the voltage isn't too critical, what is critical is the frequency. The 60Hz frequency must be critically maintained by the grid for various reasons and if you put a frequency counter on your AC, you will usually see the frequency as 60.00 Hz, to maybe briefly as 59.99 to 60.01Hz, and even at that, this might simply be random counter error in the circuit and not even the line.

Yes....absolutely. there are HUGE filters in every switchyard that filter the power before it goes to distribution lines and more filters at transmission switch yards. TRANSMISSION power is at only 15 hz instead of 60.....AC is very easily transformed. This is due to the skin effect at higher voltages and frequencies. In fact inside the new gas breakers the bus inside is a 4"-6" silver tube. Kinda whacked but that's all they need. But it's sealed inside a ceramic lined pressurized tank which is filled with an insulating and cushioning gas. Power goes out the halo into the lines.
(I have built some switchyards where I buried some very pretty conduit work for the control cabinets)

 

[toobfreak]

Yes....absolutely. there are HUGE filters in every switchyard that filter the power before it goes to distribution lines and more filters at transmission switch yards. TRANSMISSION power is at only 15 hz instead of 60.....AC is very easily transformed. This is due to the skin effect at higher voltages and frequencies. In fact inside the new gas breakers the bus inside is a 4"-6" silver tube. Kinda whacked but that's all they need. But it's sealed inside a ceramic lined pressurized tank which is filled with an insulating and cushioning gas. Power goes out the halo into the lines.
(I have built some switchyards where I buried some very pretty conduit work for the control cabinets)

Skin effect, John? Few people here are going to understand what you are talking about! You are getting into some pretty deep physics. But interesting stuff if you have the mind for how the electron works.