# Tag Info

### How can tiny MOSFETs be rated for relatively high current?

This is more of a "fusing" question, so I'll give a "fusing" answer: Fusing current is quite high for short durations. A 1mm copper wire (about 18 AWG) claims 83A for 10s, 250A ...
• 41.1k

### How can tiny MOSFETs be rated for relatively high current?

Clearly some impractical conditions are being imposed, nicely described by Tim Williams. Here is an approach to estimating a more practical limit. They provide the Junction-to-Ambient thermal ...
• 2,822

### How can tiny MOSFETs be rated for relatively high current?

They're being kind of dishonest. A bit, anyway. That 343A figure in Absolute Maximum Ratings is stated as 'Silicon Limited'. Look at the fine print in Note 1: From the data sheet. Got to watch out ...
• 55.2k

### How can tiny MOSFETs be rated for relatively high current?

Package limit is 195A, and that is with the case held to 25°C, a practical impossibility in most situations. The lead length is short and we don't know what they are assuming for the termination of ...
• 409k

### Max amps and voltage CAT5e

At 500mA for your camera, the IR drop for that length of run will probably be unacceptable. You will be facing some reliability issues. You could try it (use at least two pairs for your power, one ...
• 55.2k

### Max amps and voltage CAT5e

Your problem will be the ~10 ohms of resistance in the 400 ft round trip cable run which will drop your 12V to 7V at full load. You will need to supply more than 12V to the line - 24V is a convenient ...
• 20.8k

### Effect of limiting current of a lithium cell

If you're asking about what happens to the extra current a battery is capable of supplying, you're thinking about it wrong. If a battery can supply 10 A and you put a load on it that draws 1 A, the ...
• 25.6k

### is there any way to add amps to a vintage battery charger using an additional transformer?

You have transformers salvaged from microwave owens? If yes and you are going to use them, your life can get short. If you connect one to the mains AC only to see does it still be ok you generate ...
• 59
Accepted

### How do you specify the requirements for 3-phase load center (breaker box)

The table is a bit misleading - it's a tiny detail but important. Instead of the column label "Phase", it should be "# of Phases". That's the meaning of what you have: #Phases ...

### What is the most electricity that can be transmitted over a typical power line of the US electricity grid?

Simple: as much as it's designed for. Extant examples can be pointed to, but they're just that, examples; they aren't at all fundamental design limits, nor of technology, material or physics. These ...
• 41.1k

### Max amps and voltage CAT5e

Simply put, why reinvent the wheel here? This is precisely why there are standards for Power-over-ethernet (PoE). Sticking to the standard approach also means you don't find yourself frying devices if ...

### Q point and dc biasing

Basic idea This is not a specific transistor circuit idea only. It is a general idea that can be seen everywhere around us where some quantity oscillates. Obviously, to get the maximum deviation in ...
• 17.8k

### Q point and dc biasing

I've already spent time telling you how at this answer. But let's do the same thing but now with these curves. Let's consider the case with $V_{_\text{CC}}=12\:\text{V}$ and where \\$I_{_\text{C}}=9....
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### Is this PSU safe for this Christmas light string

Manufacturers (ab)use convenient connectors all the time, especially for nonstandardized cases like low voltage holiday lighting strings. The fact that part A plugs into part B is not a guarantee that ...
• 20.8k
Accepted

### Fans with presumably same cooling performance but significantly different current

Power consumption doesn't tell you anything about cooling performance. For a portable device, of course the power consumption is an important parameter but there are some other important parameters, ...
• 37.1k

### How do you specify the requirements for 3-phase load center (breaker box)

Another answer came up with 180 - 190 A per phase. I think that is basically correct and that points to a standard 200A load center. But there is one very important key to this being correct: Circuit (...

### How do you specify the requirements for 3-phase load center (breaker box)

You need to ask how will these circuits be used. The load center should be rated to meet or exceed the rating of the main breaker. The main breaker should generally be rated to match the service you ...
• 22.8k
Accepted

### Trouble getting current form BLDC generator

one can hear how the rpms get low. You're pedaling the bike. It's on you to keep the RPMS constant. If you can't, then the RPM goal is set too high :) The plan is to rectify the voltage using a ...

### Which one will turn the ceiling fan faster? Current, voltage, or power?

For a given fan, you only have one degree of freedom: if you set a voltage, then there is only a single possible current (and a single possible power). And if you set a current, then there is a single ...
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### is there any way to add amps to a vintage battery charger using an additional transformer?

One way to look at the transformers is that a core size (in a specific frequency) can deliver a fixed maximum power. This is because the core can store a limited amount of energy in each cycle. If you ...
• 1,883
Accepted

### What phase transformer is this? How do I calculate the FLA for this kind of transformer?

Will the transformer that these lines are feeding into also be considered a 3 Phase Transformer? Or will it be considered a 1 Phase Transformer? It's a single phase transformer with primary connected ...
• 465k

### How to measure inrush current over 3 minutes

A Tektronix scope with a current probe. Most of the newer tek scopes can measure in the minutes range. If you needed to catch a spike you could trigger. Othwise set it into roll mode and integrate ...
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### Max amps and voltage CAT5e

It's quite likely that the camera needs close to 12 volts to work and, with 0.5 amps running down 200 feet of cable, it's my judgement that the volt drop and voltage perturbations seen on the camera ...
• 465k
Accepted

### Bypassing battery to power car while camping

I believe that automotive air conditioner compressors are normally driven by the engine, so using a battery charger won't help with that. For charging phones and laptops, and running other 12 Volt DC ...
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### Tools to measure amperage load on a curcuit in a finished setting

You can use a clamp-on meter without needing to get to the wires. You need something called a line splitter. It plugs into an outlet, then you plug your load into it. It separates the conductors so ...
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### Tools to measure amperage load on a curcuit in a finished setting

An inline meter (like a kill-a-watt) can tell you what your equipment is drawing but if you want to see what the other equipment on the circuit is drawing, you'll probably need a clamp-on meter at the ...
• 20.8k
Accepted

### How can an AC adapter push 11A but only suck 2A?

You're misunderstanding what the AC adapter is actually doing. In your mind, you think it is taking in some amount of current, and then has to "push" that same current back out. That's not ...

### Can you help me understand W=I*V - house load

It says it's 150w, with 240v ac input and 2.5a. 2.5A * 240v = 600w - am I missing something? Several somethings, but the big one is that the ratings you find on the labels or nameplates of most ...
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$$P = VI$$ $$P_{IN} = 120 \times 2 = 240 \ \text W$$ $$P_{OUT} = 20 \times 11.5 = 230 \ \text W$$ No real problem there. The numbers will be somewhat approximate. I wouldn't expect the ...