Power Education

TI is unleashing the power of silicon carbide with a new, verified reference design that provides an overview on how to implement a three-level, three-phase SiC based DC:AC grid-tie inverter stage. In this video you will learn the advantages of a three-level topology; what TI technology is driving the SiC MOSFETs;  how and where are we sensing V & I; what is behind the digital power controller; and what efficiency and power density levels you can achieve with this design. Tune in as TI discusses this innovative technology at the Applied Power Electronics Conference.

What hazards might be posed by a circuit with excessive current going through its conductors (excessive as defined by the conductors’ ampacity)? In other words, what would be bad about a wire carrying too much current? Also determine which type of component fault, an open or a short, would most likely be the cause of excessive current in a circuit.

PARTS AND MATERIALS Low-voltage AC power supply Bridge rectifier pack (Radio Shack catalog # 276-1185 or equivalent) Electrolytic capacitor, 1000 µF, at least 25 WVDC (Radio Shack catalog # 272-1047 or equivalent) Four “banana” jack style binding posts, or other terminal hardware, for connection to potentiometer circuit (Radio Shack catalog # 274-662 or equivalent) Metal box 12-volt light bulb, 25 watt Lamp Socket A bridge rectifier “pack” is highly recommended over constructing a bridge rectifier circuit

Inductors do not have a stable “resistance” as conductors do. However, there is a definite mathematical relationship between voltage and current for an inductor, as follows: You should recognize the form of this equation from the capacitor chapter. It relates one variable (in this case, inductor voltage drop) to a rate of change of another variable (in this case, inductor current). Both voltage (v) and rate of current change (di

PARTS AND MATERIALS Two 6-volt batteries One 9-volt battery Actually, any size batteries will suffice for this experiment, but it is recommended to have at least two different voltages available to make it more interesting. CROSS-REFERENCES Lessons In Electric Circuits, Volume 1, chapter 5: “Series and Parallel Circuits” Lessons In Electric Circuits, Volume 1, chapter 11: “Batteries and Power Systems” LEARNING OBJECTIVES How to connect batteries to obtain different voltage levels SCHEMATIC DIAGRAM ILLUSTRATION

Things start to get complicated when we need to relate two or more AC voltages or currents that are out of step with each other. By “out of step,” I mean that the two waveforms are not synchronized: that their peaks and zero points do not match up at the same points in time. The graph in figure below illustrates an example of this. Out of phase waveforms. The two

Normally, the ampacity rating of a conductor is a circuit design limit never to be intentionally exceeded, but there is an application where ampacity exceedance is expected: in the case of fuses. What is a Fuse? A fuse is an electrical safety device built around a conductive strip that is designed to melt and separate in the event of excessive current. Fuses are always connected in series with the component

Most students of electricity begin their study with what is known as direct current (DC), which is electricity flowing in a constant direction, and/or possessing a voltage with constant polarity. DC is the kind of electricity made by a battery (with definite positive and negative terminals), or the kind of charge generated by rubbing certain types of materials against each other. Alternating Current vs Direct Current As useful and

PARTS AND MATERIALS Low-voltage AC power supply (6-volt output) Two 1N4001 rectifying diodes (Radio Shack catalog # 276-1101) Small “hobby” motor, permanent-magnet type (Radio Shack catalog # 273-223 or equivalent) Audio detector with headphones 0.1 µF capacitor One toggle switch, SPST (“Single-Pole, Single-Throw”) It is essential for this experiment that the low-voltage AC power supply is equipped with a center tap. A transformer with a non-tapped secondary winding simply will not work for

Wiring for AC and DC power distribution branch circuits are color coded for identification of individual wires. In some jurisdictions all wire colors are specified in legal documents. In other jurisdictions, only a few conductor colors are so codified. In that case, local custom dictates the “optional” wire colors. IEC, AC: Most of Europe abides by IEC (International Electrotechnical Commission) wiring color codes for AC branch circuits. These are listed

Label where each of the following electrical quantities would be found in both the “Y” and “Delta” three-phase configurations: Phase voltage Line voltage Phase current Line current In which circuit (Y or Delta) are the phase and line currents equal? In which circuit (Y or Delta) are the phase and line voltages equal? Explain both answers, in terms that anyone with a basic knowledge of electricity could understand. Where phase

Three-Phase Alternator Let’s take the three-phase alternator design laid out earlier and watch what happens as the magnet rotates. Three-phase alternator The phase angle shift of 120° is a function of the actual rotational angle shift of the three pairs of windings . If the magnet is rotating clockwise, winding 3 will generate its peak instantaneous voltage exactly 120° (of alternator shaft rotation) after winding 2, which will hits its peak 120° after winding 1. The

In the beam power tube, the basic four-element structure of the tetrode was maintained, but the grid and screen wires were carefully arranged along with a pair of auxiliary plates to create an interesting effect: focused beams or “sheets” of electrons traveling from cathode to plate. These electron beams formed a stationary “cloud” of electrons between the screen and plate (called a “space charge”) which acted to repel secondary electrons

Impedance Matching Because transformers can step voltage and current to different levels, and because power is transferred equivalently between primary and secondary windings, they can be used to “convert” the impedance of a load to a different level. That last phrase deserves some explanation, so let’s investigate what it means. The purpose of a load (usually) is to do something productive with the power it dissipates. In the case

Mercury Standard Cell Back in the early days of electrical measurement technology, a special type of battery known as a mercury standard cell was popularly used as a voltage calibration standard. The output of a mercury cell was 1.0183 to 1.0194 volts DC (depending on the specific design of cell), and was extremely stable over time. Advertised drift was around 0.004 percent of rated voltage per year. Mercury standard cells were sometimes known

Parts and Materials 6-volt battery 6-volt incandescent lamp Jumper wires Breadboard Terminal strip From this experiment on, a multimeter is assumed to be necessary and will not be included in the required list of parts and materials. In all subsequent illustrations, a digital multimeter will be shown instead of an analog meter unless there is some particular reason to use an analog meter. You are encouraged to use both types

PARTS AND MATERIALS Two 6-volt batteries Carbon pencil “lead” for a mechanical-style pencil Potentiometer, single turn, 5 kΩ to 50 kΩ, linear taper (Radio Shack catalog # 271-1714 through 271-1716) Potentiometer, multi turn, 1 kΩ to 20 kΩ, (Radio Shack catalog # 271-342, 271-343, 900-8583, or 900-8587 through 900-8590) Potentiometers are variable voltage dividers with a shaft or slide control for setting the division ratio. They are manufactured in panel-mount as well as breadboard (printed-circuit board)

Most AC motors are induction motors. Induction motors are favored due to their ruggedness and simplicity. In fact, 90% of industrial motors are induction motors. Nikola Tesla conceived the basic principals of the polyphase induction motor in 1883, and had a half horsepower (400 watt) model by 1888. Tesla sold the manufacturing rights to George Westinghouse for $65,000. Most large ( > 1 hp or 1 kW) industrial motors are poly-phase induction motors. By poly-phase, we mean that

Consider a circuit for a single-phase AC power system, where a 120 volt, 60 Hz AC voltage source is delivering power to a resistive load: (Figure below) Ac source drives a purely resistive load. In this example, the current to the load would be 2 amps, RMS. The power dissipated at the load would be 240 watts. Because this load is purely resistive (no reactance), the current is in phase with the voltage, and

So far we know that AC voltage alternates in polarity and AC current alternates in direction. We also know that AC can alternate in a variety of different ways, and by tracing the alternation over time we can plot it as a “waveform.” We can measure the rate of alternation by measuring the time it takes for a wave to evolve before it repeats itself (the “period”), and express this

How is it possible to assign a fixed value of voltage or current (such as “120 volts”) to an AC electrical quantity that is constantly changing, crossing 0 volts, and reversing polarity?