43

It is more efficient to transmit DC using about the same infrastructure. This is because of several effects: Skin effect experienced with AC. There is no skin effect with DC. Higher voltage allowed with DC for the same transmission lines. The lines have to withstand the peak voltage. With AC, that is 1.4 times higher than the RMS. With DC, the RMS and ...


41

I actually worked on HVDC schemes, back in the mid-to-late 90s. Olin Lathrop's answer is partially right, but not quite. I'll try not to repeat too much of his answer, but I'll clear up a few things. The losses for AC primarily come down to the inductance of the cable. This creates reactance for AC power transmission. A common misconception (repeated by ...


7

They're talking about complexity and costing (\$\$\$\$\$) The people saying "DC is less efficient" are using the word "efficiency" to talk about design factors like complexity of conversion hardware, and more critically, its cost. If we have a Santa Claus machine that can pop out DC/DC converters as cheap and reliable as comparable transformers, then DC ...


5

The math doesn't make any engineering sense. A 5MW turbine typically rotates at about 10 RPM, near enough 1 radian per second. Assuming you had reasonably big sprockets on the chain drive, say 2 meters diameter (!!) the linear speed of the chain would be 1 meter /second, and the tension in the chain would be about 5MN or about 500 tons force. Something ...


5

Trains do sometimes use different means for propulsion: Rack railways use cogs, and Funiculars use ropes I think the reason these are uncommon is that the available traction of smooth tracks is more than sufficient for all but really steep slopes (>10% ). Train engines may be limited in both torque and power when it comes to moving a heavy train up a steep ...


5

There are a few possible reasons. Elimination of electrolysis problems with ground connections. Elimination of variations in ground resistance. Grounding one of the conductors on the HVDC line might save money on isolators, ... Using a ±½VDC on each wire is common. If transmitting, say, 500 kV DC then one wire is +250 kV DC and the other is -250 kV DC. ...


5

Because they're both live Just because you see multiple wires doesn't mean they are carrying different things. They are frequently paralleled for more ampacity. It's perfectly common in HVDC lines to use earth as the return path. For instance, the Pacific Intertie does just that, with absolutely massive grounding electrodes at each end. The grounding ...


4

Because it is not a power cable (Q1) using power connectors (Q2). BNC cable has a solid conductor and a ground braid to electrically shield and mechanically protect the conductor. Electrical reason: Some ground braids are made of steel, which is not as good a conductor as copper, so voltage losses to the wire would be higher than copper wire. Basically, ...


4

Note the problem specifies the load is "delta connected". There is no neutral connection to measure phase voltage ($V_{LN}$) against. Also note the supply frequency is 60 Hz. 208 V is a common line voltage ($V_{LL}$) in the US (which uses a 60 Hz supply), with corresponding phase voltage of 120 V. You are using a US text (Sarma et al, from another ...


3

I think this question is about additional cross bracing. With a rectangular frame in a vertical plane the ability to carry compressive loads is excellent, but a comparatively small lateral force can deform the rectangle into a parallelogram which will collapse under the same loading. Since the cross bracing will operate to restrict primarily tensile and (to ...


3

This is more of an addition to the previous answer by blacksmith37. I think it might be more appropriate as a comment, or perhaps an edit to the previous answer. With no ability to comment at this time, I'll leave the next step to people smarter than myself. I believe this is a fairly straightforward answer: How they predict the amount to generate How ...


3

Here you go: https://uk.rs-online.com/web/p/spur-gears/8787907/ The trouble is that a 1MOD 12 Tooth gear has a pitch diameter of 12mm, i.e.the bottom of the teeth is less than 12mm, so once you drill a 6mm hole through the middle there's really not much material left at all to make a hub from. What is the specific requirement or constraint that means you ...


3

Your terminology is correct, but also sometimes called bevel gearboxes. A cheap off the shelf unit is a few hundred dollars. If that is too expensive you probably won't save any money designing and fabricating the gears and housing yourself. A u-joint is a cheaper alternative. But if you are intent on making your own, Boston Gear has good catalogue parts and ...


3

these things are sold cheaply (less than $20) for bending the output of an electric drill through 90 degrees, so you can drill holes in cramped places. they can handle from 1/4 to 1/3 horsepower typically. hardware stores sell them. they are called right angle drill drive attachments.


3

Multiple Clutches Many manual transmissions feature just a single clutch between the engine and the transmission. This requires that the clutch be disengaged before switching gears, during the switch, and until the final selected gear is fully engaged. When a human is performing this operation, the clutch may be engaged for many hundreds, even thousands of ...


3

TL;DR:IMHO, the driver for keeping the electrical generation closer to the hub is for primarily for eliminating -as much as possible- moving parts for safety concerns. The secondary benefit is the reduced losses. IMHO the problem is the distance and the complexity. For the following examples I will use as an example a Wind turbine with the following ...


2

If you imagine a square or rectangular shape made from rods joined with points at the corners. If those pins act as hinges then the whole shape can easily deform, effectively acting as a 4 bar link. On the other hand if the shape is a triangle then even if the corners are hinged then it can't be deformed without stretching one of the bars. Also, whichever ...


2

a shock load on gearing is imposed when the gear train is forced to start or stop turning very suddenly, or when a heavy load is suddenly applied to a set of rotating gears. A good example of this is when the driver of a car with a manual transmission slams or "bangs" the gear changes without skilled use of the clutch, causing the car to suddenly lurch. This ...


2

All else being equal DC transmission is more efficient than AC transmission at the same nominal voltage due to the elimination of reactive losses. However all else is rarely equal. At a given voltage DC is far more prone to sustaining arcs than AC. It is only relatively recently that we have developed the ability to convert between DC voltages with ...


2

With the high voltage AC power lines, there are trade offs between losses due to resistance in the wires, where the higher voltages are better and losses due to capacitance to the air, etc. where lower voltages are better. That is why many big, high voltage power transmission is done with DC these days. For example, the 500 kVDC line from the Intermountain ...


2

The transmission ratio is related to the number of teeth on the worm gear, and the number of starts on the worm. In your case, $$i=\frac{z_{worm\ gear}}{z_{worm}}=\frac{25}{1}=25$$. This means that you have a reduction of $25:1$, so, assuming $100\%$ efficiency, you would expect your output Torque to be 25 times higher than your input torque, and your ...


2

What are the respective tolerances on the “6mm”? Either it will be a press fit which will be sufficient to handle the torque and shock loading or it will not. If not, then you have to fit set screws and even machine a flat on the shaft.


2

Boston Gear or McMaster-Carr might have suitable off the shelf gears. You could also press the gear onto a hub that has a set screw. I would avoid pressing anything directly onto a motor shaft, you could bend the rotor and/or damage the internal bearings.


2

That might be overkill in your application (but I don't know). Figure 1. A random rigid flange coupling from an image search. A rigid flange coupling may be a more economic choice if it suits. From the comments: What are the benefits of a rigid flange compared to a split flange beside costs? Doesn't the flexible coupler give more friction? A flexible ...


2

you can use a pantograph belt. They use them in large machines to transfer rotation to a moving drill to cut squares and what not. Basically they are several pullies assembled on a pantograph with links designed to move as prescribed.


2

I don't know why the other answers are talking about CVTs. Maybe I'm missing something? But the basic way how automatic gearboxes achieve smooth switches is that they use multiple clutches, instead of moving / remeshing gears. For example this site shows basic structure of the 10R80: Typically the clutches lock up the sun gears of a planetary gear system, ...


2

Although probably not what you are after, there is Power-over-fiber, which is a technology analogous to "Power-over-Ethernet". To be honest, I haven't seen any devices that take advantage of this capability, although this can be because fibre optics devices are not as common (?) as ethernet devices. The idea behind a PoF system is able to provide ...


2

I think this will lead to an overestimation because you are assuming the load is 100% during the whole time (I would expect it to be somewhere 40 and 50% on average). Assuming 35 MJ/L, your calculation as it is would yield about 15 L per 100 km, which is too much. Given the average ratio of load, it would yield something between 7.5 and 6 lit per 100 km ...


2

Tip: 'KW' is a kelvin-watt (which I don't think is useful for anything). Use 'kW' for kilowatt. (Capitals matter!) You could really simplify the problem by using the energy density of the fuel. If you look it up you should find that it's about 10 kWh/kg of petrol or diesel. 10 kWh/kg × 3600 s/h = 36000 kWs/kg = 36000 kJ/kg = 36 MJ/kg. My diesel VW does about ...


1

It is a spring-loaded ratchet and pawl system. the pawl mechanism is unlocked by the centripetal force of the initial rolling of the shade by a user. Here is a diagram.


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