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9

There must be a solder joint of a component which is broken. A mechanical shock moves the component and it makes contact again. That could be a fire hazard, not to mention more components coming loose in their solder joints due to all the mechanical shocks. Please buy a new adapter.


3

You can not connect BLDC motors in series. It is possible to connect the armatures of two commutator type DC motors in series with the shafts mechanically coupled together essentially driving the same load. Torque sharing is accomplished by separately adjusting the field currents. There is not likely any other type of motor that will work with any type of ...


2

Assuming that the three feed voltages are balanced and are sine waves i.e. line voltages are identical with exactly 120 degrees between them, any star connected load of equal values will produce 0 volts at the star point. This means that three identical resistors will yield 0 volts AND three identical inductors (or capacitors) will also yield 0 volts. With ...


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A capacitor on the AC side won't do what you seem to think it will do. A capacitor will pass AC. If you put a large capacitor across your AC source, it will in effect be a (near) short circuit - cue sparks and bangs and tripped circuit breakers. If you put a large capacitor in series with your AC source, then still won't help. It will act like a ...


2

Can 5V kill you? Short answer: YES ...BUT....you'd have to broach the skin to subcutaneous layers or have lots of blood exposed in positions either side of the heart. So with a frayed USB cable (both ground and +5V exposed) an impossibly low risk for such local contact. If your skin is intact the likely resistance is in the 10-100 kOhms range, so death ...


2

I want to generate a sinusoidal electromagnetic field of a specificed frequency between 30-80 Hz....What do I generate an ac current of the specified frequency? You need to buy a signal generator or build an oscillator. If it must be capable of generating any frequency in the specified range, it must have an adjustment that covers the range. An amplifier ...


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I have never tried it, but I am pretty sure if I put a live wire on my floor, nothing will happen, right ? Electricity will flow through the floor to ground or whatever object has a different voltage potential than it. The resistance of the floor will probably be high, so not much current. The capacitance of the wire with other objects will also allow ...


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The synchronous motor/generator has two power ports, a mechanical power port at the shaft and electrical power port at the motor/generator terminals. Because mechanical losses and magnetic losses (core and stray losses) are (approximately) proportional to the motor’s rotational speed, they are often taken together and referred to as rotational losses. ...


2

According to answers to this question: The breakdown voltage of air varies significantly due to changes in humidity, pressure, and temperature. However, a rough guide is that it takes 1 kV per millimeter. Therefore your 25 kV overhead rods will be adequately spaced from the ceiling at a minimum of 25 mm / 1 inch; it looks like they have several ...


1

@Finbar's suggestion is the easiest and safest if you just want to plug it in and don't care about response time. Use a genuine safety-agency approved charger, not some dollar store item made of Shenzhen street sweepings, some of them are very bad (and unsafe) indeed. You should add a bleeder resistor to drain the output votlage in a reasonable length of ...


1

I believe that your power supply contains a mechanical component that no longer switches due to aging. This could be a mechanical relay or a bimetal connection where I'd rather guess a mechanical relay.


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Considering you are applying a low loss 2k source R to a 50k Load with a nominal input of 339Vp to a 250V 0.1uF ceramic cap, it is no wonder that it failed. The only choice here is an X2 rated film cap which attenuates 1kV To 3kV lightning transients as per your unstated CE requirements. Start with worst case power & transient specs, then your ...


1

Core or iron losses are not mechanical. They are mainly due to frequency and voltage, so they are constant. Eddy currents (batteries set up by impurities in the iron) and hysteresis (heat created by reversing magnetic field) are the main iron losses. Eddy currents are the main reason the core is made of laminated segments.


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5 nF has an impedance at 50 Hz of 637 kohm so it's unlikely that any damage will have occurred because the maximum continuous current (even into a short circuit) from 240 volts AC is limited to only 0.4 mA. This might rise to about 0.5 mA if your supply is 60 Hz. Given that an ignition coil is used to having several amps applied to the primary in order to ...


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I don't think having neutral and phase reversed at the fridge would cause any problems, it does not make sense to make these fridges polarity sensitive as in many countries you can freely plug it any way you like. Also D202 is definitely not a part of full bridge rectifier. Full bridge rectifier can almost be seen above the fuse and the big 450V capacitor, ...


1

If you touch a 230V live wire with dry hands, the current through your body is roughly 2 mA. This isn't enough to make an RCD switch trip but its actually quite enough to harm you. Contact surface area matters, too. A wire lying on the ground only has a very small surface where it is actually touching it. It's two hard objects. This is different already ...


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All the energy in a gapped magneto or coil is in the air gap. Gapped cores being very small look like a point source from a distance and reduce in B field by 1/r^2. Saturation depends on voltage and inductance producing a B field flux that exceeds the core Bsat rating. It does not depend on load current but rather the excitation current from V/L and ...


1

It is all about electrical power and energy. An arc need a higher voltage so that the jolt of electricity can jump over(or through) air. This is why more voltage is needed than current. And a heater needs more current than voltage. When current goes through a wire it can produce heat. The heat power is p=I^2.R More the current is there, more the conductor ...


1

Being exposed to 5V for extended times is absolutely harmless. Nothing to worry about. However, you should still replace the cable. A frayed cable can create partial for full shorts and these can damage the charger or the phone and result in things overheating or breaking. The cable connector itself could get hot too.


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This is a great question Colin, one which I puzzled over long and hard myself before coming to an intuitive understanding. Magnetizing inductance and magnetizing current are two aspects of the same departure of a real transformer from the ideal transformer model; in particular, as you mention, the fact that a real transformer core has finite permeability. ...


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