39
votes
Accepted
Why is it harder to turn a motor/generator with shorted terminals?
I have to start with some terminology -- sorry if it's esoteric, but this will bring things into line with how folks talk about this subject.
When you turn a permanent-magnet DC machine*, the ...
- 46.7k
29
votes
Accepted
Does a generator produce voltage or current?
Internally, a generator produces voltage proportional to its speed.
However, that doesn't mean a constant voltage always comes out of a generator run at a fixed speed. The windings and other parts ...
- 314k
27
votes
How can I generate voltage for a science project?
Buy power supplies. No, really. These things are produced in large quantities and sold into a competitive market. Leave the safety design and regulatory approvals to someone else. Anyone that has ...
- 314k
26
votes
Accepted
Advantage of using AC generators in cars instead of DC generators
No, it's not for efficiency reasons.
DC generators typically have commutators, i.e. contacts with brushes that reverse the polarity of the voltage at the generator clamps every half rotation. In ...
- 98.3k
26
votes
Accepted
Can we tell which way AC power is going through a cable without cutting the cable?
A cable consists of two conductors, with a finite space between them. Let's assume they're insulated.
Use capacitive sensing to determine the polarity of the instaneous voltage between them as a ...
- 171k
21
votes
Is it safe to touch 200 volts DC?
No, most electrical regs class low voltage “safe” as below 50V DC
It is not the max current but where it travels through the body and, also, when in the heart cycle it hits...
So, don’t play.
- 6,549
20
votes
Accepted
Is it safe to touch 200 volts DC?
The content maker simply declared that 200/300 volts DC is safe to touch.
He didn't say this anywhere in the video, and he didn't imply it either. In the first few seconds he says:
I want to kick ...
- 316
18
votes
Laptop failure due to constant fluctuation of AC frequency and voltage
Don't worry. Your PSU doesn't really work with AC.
Most modern PSU fist change the AC to DC via a rectifier. The internal electronic then creates an own AC used to transform the voltage to the ...
- 364
15
votes
How can I generate voltage for a science project?
I believe your current requirements will be modest for electrophoresis.
Consider a string of 9V batteries, which will be inexpensive ($7 at the dollar store for Panasonic batteries) and relatively ...
15
votes
Advantage of using AC generators in cars instead of DC generators
The alternator HAS to generate A LOT of amps at a very wide range of rotation speeds. Further the electrical load can and will change drastically from moment to moment.
A fixed magnet dynamo would ...
- 46.9k
14
votes
How to connect two wildly different power sources?
There are some single-chip solutions for this exact situation, called OR-ing controllers.
While most of them are designed for use at low voltages (e.g. the TPS211xA, limited to 5.5 V) there are some ...
- 36.5k
13
votes
Generator burnout
It should have said safely provide.
But also, there's often a confusion between drawing power and drawing current.
For example, you can get the maximum power out of any voltage source if your load ...
- 98.3k
12
votes
Accepted
Source of initial magnetic field in an alternator
The initial field excitation, in an automotive alternator, is provided by the battery.
In an automotive alternator, AC output from the star-connected 3-phase winding is rectified by a 3-phase full-...
- 19k
12
votes
Can we tell which way AC power is going through a cable without cutting the cable?
Since you can measure
the electric field (red arrows) between both lines of the cable and
the magnetic field (green arrows) around each line of the cable
without cutting it,
you can determine the ...
- 16.4k
9
votes
Accepted
What is the maximum possible current that can mains supply can deliver?
The answer is not infinity, even 'theoretically'.
There are at least 3 defined currents for any point on the supply, and that point can be anywhere from the terminals of a nuclear power station, down ...
- 171k
9
votes
Fruit juicer motor generates very low voltage
This depends on the type of motor. Not all motors work like generators without any electrical power applied. For example, if this is a AC induction motor, then it is only due to accidental residual ...
- 314k
9
votes
Why are Marx generators built like that?
You could use a parallel arrangement of resistors, but you would need very high voltage resistors, and clearances round them. The main point of a Marx is to get a very high output voltage with ...
- 171k
9
votes
Accepted
How/where does a generator + motor dissipate heat?
The motor uses most of the input power to cause motion, not to generate heat. A 1kW motor that made 1kW of heat from 1kW of electrical power would be a very poor motor - it would more commonly be ...
- 73.1k
9
votes
Accepted
Is the overvoltage protection used in this circuit a normal way of doing it?
Is the overvoltage protection used in this circuit a normal way of
doing it?
I've seen it done this way. It's basically equivalent to a programmable zener diode i.e. nothing is shorted out; if the ...
- 467k
9
votes
Accepted
Does speeding up a diesel generator result in a better load response?
Higher RPM will proportionally raise the peak power a diesel engine can deliver - up to a point, of course.
But 62Hz is just 3% more than 60Hz, so it's not very relevant. You can get similar variation ...
8
votes
Accepted
Fruit juicer motor generates very low voltage
The rotor of AC asynchronous motors is simply a lump of aluminium and iron. As there isn't any magnetically hard material involved, there is little to no residual magnetism stored and so, the motor, ...
- 14.4k
8
votes
Accepted
What is the purpose of perpendicular "smaller" magnets in between the main magnets in a rotor of a motor? had never seen this before. Do they help?
This is more or less just transferred from Wikipedia, however:
As @HarrySvensson indicates, this is a Halbach array, apparently used to create a magnetic field that is stronger on one side than the ...
- 4,143
8
votes
How to test power output of an 8.5kW generator?
Borrow some electric kettles from your friends, or buy a couple, they're not that expensive.
They're compact, and light when empty.
They have a very predictable current draw, not something that ...
- 171k
8
votes
Accepted
Does Alternator Self-Excitation Require Rectification?
All simple alternators with wound rotors (such as on cars). Do rectify the output of the stator to provide the field current.
The exact arrangement may vary but a common arrangement is shown below.
...
- 33.8k
8
votes
AC vs DC voltage regulator for hybrid drone
The answer to your question is that regulating DC is much easier than regulating AC. But I also want to comment on a few things.
First, you mention that your gas engine speed will vary a lot. Why is ...
- 29.4k
8
votes
I am running 10 kVA alternator from 10 hp motor and need some technical clarification
Whenever the load increases more than 10 A on alternator the output voltage starts decreasing.
Very common of small alternators. In fact, so common that most gasoline generators today are inverter ...
- 1,876
8
votes
Why is my inductor behaving like a capacitor?
The supply's power switch is not the way to implement this, since it's on the wrong side of its own output circuitry. That output no doubt consists of a capacitance right across it. Maybe the circuit ...
- 42.2k
7
votes
What makes automotive alternators so inefficient relative to other applications?
Voltage: at 14v it is very hard to be efficient.
diodes loss: car alternator operate around 14v, with 0.6v for each diode pass you have 1.2v loss: almost 10% loss only this one.
windings: you loose a ...
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