# Tag Info

39

Safety capacitors are classified by X and Y ratings. Let's properly define everything, and then it should become clear how those capacitors can be rated for both X and Y at the same time. Class X Capacitors: These are capacitors are only for use in situations where their failure would not present an electric shock risk, but could result in a fire. That ...

13

It seems perfectly feasible to dump the load into a 1 kW wirewound resistor using a mosfet. Example resistor: Vishay p/n FSE100022ER500KE This is a 1 kW wirewound resistor rated for 10x overload for 5 seconds. This will have no problem handling 100 Amps for 200 ms as long as you don't do it over and over. Cost is around 80 US dollars in single unit quantity. ...

10

The snubber provides a lossy path for the inductor flyback. It's essentially a high-pass filter that shunts the flyback spike past the opening switch back to the power supply, dissipating some of that energy in the resistor, as heat. The snubber can also be placed across the coil so the spike energy is shunted locally at the coil, although this wastes AC ...

9

The primary tradeoff is the thermal management or derating features that must be considered in these combined dual roles. If a TVS device is also used as a Zener for continuous voltage regulation, the device would then be operating with sustained power dissipation where internal p-n junction temperatures are driven well above ambient from its ...

9

While it's certainly possible to design a shunt load to absorb that much energy, it would require a somewhat large and expensive pulse-rated resistor and a nontrivial semiconductor to switch it in. Instead I would take the approach of accelerating the regulator's woefully slow load-dump response: Use an op-amp or comparator to detect an overvoltage ...

6

No, X caps should fail open to prevent the risk of fire. However, there have been some parts that have caught fire after a number of years in the field. It's common wisdom that paper dielectric caps are more reliable because paper soaked with epoxy self-heals better than polypropylene. In some cases the epoxy has undergone some sort of fatal change. ...

5

For a transient voltage spike you can click on your voltage source and under the advanced option choose the exponential output. Here you can provide the parameters for your spike such as the rise time and the fall time. The absolute best method would be to construct a piecewise linear model (PWL). In this, model you specify the voltage output at each time. ...

5

I don't see any useful functionality for that part. In the Jameco schematic the IRF46 MOSFET used will handle very large transient currents through the body diode, which is directly in parallel. It also has a reasonably healthy 28A/11mJ avalanche rating. A reverse connection of the load will put all the source voltage (minus a diode drop) across the sense ...

5

Transil is a trademark from ST for its TVS diodes. TVS diodes behave somewhat like zener diodes: the current flows through them as soon as the voltage exceeds a given value. Contrary to Zener diodes, they are designed to get a huge power (600W and 1500W are standard power ratings) but only for a very short period of time. Moreover, they are generally ...

5

I would think a thyristor/SCR crowbar circuit on a heatsink could survive for 200ms. Except instead of crowbarring a short, crowbar into a resistance. If you're really worried you can use water submerged resistors (like hot water tank heating elements). We use something like this at my work for a continuous 4kW loads. Our setup is 4kW and is two 10 gallon ...

5

Three alternative solutions: It is perfectly safe to short an alternator output instead of dumping its excessive energy somewhere. Most permanent-magnet alternators are even regulated by PWM shorting. Here, you only need to short it for these 200ms until the field dissipates. Option: you may short all the alternator windings upstream to the rectifier to ...

4

Because you're frustrated, here is the solution first thing! :) Switch the 1V going into the top of the potentiometer, instead of the output connection. In other words, use the potentiometer to modulate the amplitude of a 2KHz 1V square wave going into the op amp's noninverting terminal. Do not open and close this terminal, 0V means at ground potential. ...

4

Calculating the peak junction temperature for a short pulse is difficult. The 226°C/W is for steady state or dissipation that is much longer than the thermal time constant of the device. The pulse rating curve (Figure 1, above) in the data sheet shows how much power the device can dissipate for a single pulse event. It's probably safe to assume that the ...

4

Diode Rd, Rs, Zt , ESR (synonymous names) or dynamic (bulk) resistance is always... Rs=ΔV/ΔI ( same applies to a Zener , Zt which has much higher ESR) you measure this at the slope of the rated power. For reduced power, the Rs slope rises or the inverse Ys falls. This value is essentially the shunt resistance the ESD device will provide under an ESD ...

4

The surge test according to IEC EN 61000-4-5 is performed on equipment whose power supply connections are geometrically far away from the device itself, in order to test its resistance to the three following stroke related events (accordig to this nice survey): Direct lightning strokes to outdoor circuits injecting high currents and producing overvoltages. ...

4

it's a actually high pass, thus it's only usable at the low frequencies. at higher frequencies there is too much heating in the resistor.

3

I've tried a similar setup and I've realized that you're using a very small sweep time (500 us). Your transient, that seems so wide in the picture, last only about 30 us. When using a quasi-peak detector it will be certainly removed. I can show you my pictures. In my setup I've used a 10 dBm signal, 868 MHz central frequency, and an offset of 200 kHz when ...

3

How about a quick calculation for power dissipation. Suppose that 5 kW (5,000 W) was going to be dissipated for 10us. And also suppose that the pulse was to be repeated every one second. You could multiply: $$\frac{5,000W \times 10us}{1,000,000 us}$$ Equivalent is: $$5,000 \times \frac{10}{10^6} = 0.05W = 50mW$$ Additionally the temperature of the ...

3

The difference between the TVS and Zener diodes is construction. A Zener diode is primarily designed to handle steady state power. The Zener functions as a voltage regulator (shunt style) or voltage reference in a power supply system. While electrically similar, the TVS unit has a different construction and is designed to absorb large amounts of energy (...

3

The device is made to handle signals which normally operate between GND and V++. Any signal line transient that goes below GND is clamped by the lower diode to a voltage that is equal to the forward voltage drop of the lower diode. So you can see that clamping will be to less than about -1V in that case. (Clamping level really depends upon how much current ...

3

(revised) The purpose of ESD (electrostatic discharge) impulse capacitor discharge tests is to simulate a static charged human finger and a metal cart on insulated wheels touching a conductive surface. These tests have various levels for acceptance criteria such as; no interference, no operator intervention and no damage. The arc is limited for the HBM ...

3

The loud pop you hear when turning on a power amp is most likely caused by DC blocking capacitors somewhere in the signal chain. Suppose you have to connect two stages together, for example the input stage and the pre amp stage of your amplifier. For design reasons, the output of the input stage has an output DC voltage of 1 V, while the input of the pre ...

3

A TVS has six key parameters Ppp Peak Pulse Power. This is the power rating of the devices and should not be exceeded. Take care of temperature derating and design margin de-rating Ipp Peak pulse current. Vwm Working voltage. This is the voltage at which a TVS is guaranteed to to conduct more than the leakage Vbr(min) This is the minimum voltage the TVS ...

3

I suggest a twofold strategy: use low inductance capacitive shunting around your laser diode. The laser has an instantaneous resistance of several ohms (Vf / 180mA). So build something that is in the mohms for frequencies above e.g. 10 MHz, e.g. using MLCCs. In addition, you can add an inductor/bead in series with the laser. a semiconductor current limiter ...

3

The recently inserted schematic shows that you have a big inductor with DC current. That DC will not stop suddenly if you try to break it, but generates as much voltage as needed to decay gradually. It's seen as voltage peak in the primary. The peak is as high as needed to let the current continue as an arc in the switch and die gradually as the inductor ...

2

The other answers are good but if you prefer a one component solution there exists Inrush Current Limiters. I've used them before to prevent fuses blowing when hot-plugging the power supply. Their operation is really simple. Basically they have a resistance at room temperature, say 5Ω. When you plug in a 5V power source the surge current is now limited to ...

2

You can put a free-wheeling diode at the pump leads. Any regular rectifier diode will work. Put the diode in reverse (diode anode on negative side of pump and diode's cathode on positive lead). When switch opens, the diode will dissipate the "spark", thus extending the life of your switch.

2

TVS diodes are designed to withstand high junction temperatures those they have much larger die area than the conventional zener diodes. So don't try to calculate $T_j$ of a TVS diode at surging time, using the conventional thermal equivalent circuit. Even you cannot use the transient power-temperature or thermal time resoponse calculations as in regulator ...

2

One way would be to use a SPDT switch, add a series resistor to the inverting input: simulate this circuit – Schematic created using CircuitLab Real switches have a certain amount of charge injection so a little more finesse may be required in a real implementation. A series resistor to the gate would slow the switching edges a bit, but in that case ...

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