# Tag Info

9

Does the DC load somehow feedback and lower the resistance of the primary coil so that more power can be drawn? Yes. It would be simpler to analyze an AC load though. The diodes are not central to your question: The impedance of RL is also transformed, so if you have a 10:1 transformer and RL is 2 Ω, the AC source will see the transformer as a 200 Ω ...

3

Your understanding of the issues is good. Q1: It's not overkill at all. All of the elements you've mentioned are needed. Q2: The low-pass filter frequency needs to significantly attenuate all frequencies above 1/2 the sampling frequency. It makes sense for a 'low fi' arrangement to reduce the filter frequency a bit so as to simplify filter design which ...

3

A transformer offers resistance to AC current flow due to the magnetic field produced by the current flow. This "AC resistance" is termed "impedance" and is a function of number of turns, core material, air gaap in core , core dimensions and more. When there is no load the applied AC voltage will cause "magnetising current" to flow. This will cause some ...

2

You can have brushless DC as well, but its all a balancing game of cost over its lifetime. Efficiency only matters when the entirety of the process is considered. One high efficiency process can be useless if it forces you into a low efficiency one later. AC can be generated directly off something that rotates. If you smooth it out to DC, you lose some ...

2

Most low-power, single-phase synchronous motors are shaded-pole motors, in which a turn of copper wire is placed around some fraction of each of the poles for the main coil. This creates a phase shift in the magnetic field that causes the motor to turn in a particular direction at start-up. Note that the rotor can be a simple squirrel cage rotor that is ...

2

The wikipedia link in the answer you dismissed to ask this question gives you the answer: "A single-phase (or two-phase derived from single phase) stator winding is possible, but in this case the direction of rotation is not defined and the machine may start in either direction unless prevented from doing so by the starting arrangements " When AC is applied,...

2

It could, yes. But the tradeoff would be worse performance. The strength magnetic field is a function of distance from the coil, so increasing the volume by turning your rotor into a fan shape would reduce the efficiency. Typically, this is dealt with by close mounting a fan, sometimes inside the motor case. The motor stays compact and efficient while the ...

2

A 3Hz pulsating hum-- noise that is getting louder and softer at 3Hz. Yes, I agree that would be quite annoying. Since this is a residential unit in the US, both the compressor and the fan are run with single phase asynchronous motors. Almost certainly, they are four pole with an 1800 RPM synchronous speed, running about 1750 RPM or so, depending upon ...

1

Are you making a corrosion sensor or a hydrogen sensor ? Corrosion sensors ( corrosion probes) ,based on metal loss have been around for over 50 years. And hydrogen is a special problem , strongly dependent on the diffusion of the hydrogen. Steel is relatively "transparent" to hydrogen above 400 F. And the solubility below 400 F depends on the steel ...

1

Foundations (Energy Balance) For the Room Consider the system shown in the picture below. Air flows through a room volume (area and height) with a residence time. Heat is provided by people inside the room. The steady state energy balance equation becomes  \dot{m}_a\left( \tilde{H}_{a,out} - \tilde{H}_{a,in} \right) = \dot{q}_p \\ \left(\frac{A h}{t_{...

1

AC generators are simpler. Their inherent construction property is that the sine wave of AC is directly derived from the rotary motion of the rotor. There is no commutator, which is a part that suffers wear over the course of use of a dynamo (a DC generator). Even with a dynamo, the current isn't exactly DC, just an approximation. Neither is "better" or "...

1

This question is rather confused, but I'll take it as "Can AC power be produced from DC power without mechanically moving parts". Of course. That's what devices called "inverters" do. Most inverters are designed to work at a single frequency, but they certainly don't have to be. Think of class D amplifiers as examples. Clearly they can produce a wide ...

1

A possible avenue you could look at is the motor controllers that match power to load.

1

You really can't change the frequency of alternating current. This is fixed at 60 hertz (cycles/sec) for USA and 50 hertz most everywhere else. by laminating the permanent magnets you reduce losses to hall effect currents on the surface. Most commercial motors have already made the most efficient design possible. You can always improve but usually only ...

1

A standard induction motor has to turn at the speed determined by the current frequency. If you attempt to apply external torque to drive it faster it will act as a brake resisting that torque. If you apply sufficient torque to force the rotor out of phase with the driving current it would effectively stall ( the "braking force" dropping way off and or ...

1

You want something called a oscillator. It is powered from DC, and produces AC output, usually a sine or square wave. For the case of 10 MHz, you can use a resonant design since the components can be physically small. RF transmitters are examples of circuits that take DC power in and AC at a specific frequency at substantial power.

1

You will need variable frequency drive (VFD) with "regenerative braking" or a "braking resistor"(the cheaper option) for this application. "Braking" is not necessarily a standard feature (especially on small VFDs) so you will have to specify it. A common configuration is to have the VFD output a frequency proportional an input(0-10v or 4-20mA). They can ...

1

I've got a few of the circular motors in my junk box and took one apart. With what I've found on the net, and what I see in the unit I have, here is what I found. The circular units are for very small wattage requirements and usually are applied in equipment, like the fish tank pump and microwave turntable discussed here. The unit I have came out of a ...

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