19.02.2016

Dc current transformer wiki

Presentation about Thomas Edison and the difference between AC and DC electrical current (WGBH). In a solid metal conductor, current is the flow of free electrons (negatively charged) which move from negative to positive. In molten or dissolved electrolytes, it is the flow of negative ions (anions) towards the positive terminal and vice versa.
The power that goes into a electrical equipment in my country (the US) is 120 volts AC, 60Hz, plus or minus 10% (108 to 132 volts of alternating current at a frequency of about 60 cycles per second) .
It would be nice to have understanding of DC (direct current), This is the type of current that comes from a battery. Plus if you need to switch everything off in a hurry (if there is a short or whatever) the capacitors will continue to discharge into your circuit after you disconnect the battery.
As long as you are aware of these things and plan for them, then capacitors can be helpful in certain situations.
I was in another thread and from some of the comments, it is apparent that most people have no idea what AC or DC current really is.
Without a commutator, a dynamo becomes an alternator, which is a synchronous singly fed generator.
In our AC motors, the ESC changes the speed (RPMs) by changing the frequency of the voltage.
Typical alternators use a rotating field winding excited with direct current, and a stationary (stator) winding that produces alternating current. I'm really not being a smart ass - I was actually making reasoned suggestions and posting additional info.
If you would taken a stop watch and clocked it, you would have noticed that you were buzzing 60 times per second. The easiest way I can think to remember the difference is that with AC current the flow of electrons is back and forth in the transmission medium at whatever rate it is produced (60hz for most of us).
With DC current, the electrons flow in one direction at the speed and volume determined by their voltage and amperage.
So DC is how batteries produce power but why have we got AC, does it make it easier to send it the long distances it needs to travel along the power lines? The AC brushless motor is a true 3-phase AC motor and is described as such by the motor manufacturers themselves. Scenario: Im splitting my 3s 2200mAh 40C Lipo into ESC, separate UBEC and FPV video transmitter. Tip: To turn text into a link, highlight the text, then click on a page or file from the list above.
There are two types of electrical currents: direct current (DC) and alternating current (AC). For a given current flow, a proportional magnetic field is produced around the current carrying conductor.
The current sensor is an economical and reliable tool that is indispensable for monitoring equipment status, detecting process variations, and ensuring personnel safety. Controlling pumps, compressors, heaters, conveyors, and other electrically powered loads requires accurate, real-time status feedback. Simply stated, measuring the current input to equipment gives you more knowledge about actual equipment performance. Current sensors facilitate the automation of industrial pumping stations by allowing real-time monitoring of pumps, compressors, heaters, fans, and other powered equipment. Unfortunately, the shunt presents serious operational problems and potential safety hazards.
Since it is essentially a resistor, the shunt is often perceived as the least expensive solution. Hall effect and induction are noncontact technologies based on the principle that for a given current flow, a proportional magnetic field is produced around the current-carrying conductor.
The Hall effect sensor consists of three basic components: the core, the Hall effect device, and signal conditioning circuitry. Because the Hall sensor is totally isolated from the monitored voltage, it is not a safety hazard and has almost no insertion impedance.
Depending on the design, Hall effect transducers can measure frequencies from DC to several kilohertz. The current-carrying conductor is generally referred to as the primary and the core winding is called the secondary. Inductive sensors are designed to measure AC power and typically operate between 20 Hz and 100 Hz, although some units will work in the kilohertz range.
Current sensors are frequently used to provide essential information to automated control systems, and as primary controllers in relay logic schemes.
Variable frequency drives (VFDs) conserve energy and improve motion control through improved motor speed regulation. Most current transducers are of the average responding type, rectifying and filtering the sine wave to obtain the average peak amperage.
Only true RMS measurement is capable of accurate measurement of nonsinusoidal waveforms found on VFDs, SCRs, electronic ballasts, switching power supply inputs, and other nonlinear loads. True RMS measurement begins by squaring the input waveform to mathematically rectify the signal.
Most current transducers are available in solid or split-core configurations to facilitate installation. Automating the feed mechanism to crushers and grinders is often accomplished by installing a current transducer on the motor lead. The same control logic can be used to interlock two or more motors to ensure personnel safety. Automatic load switching and status alarming are also typical applications for current switches. Smart self-calibrating current switches can be programmed to alarm overload and underload conditions or to start up standby equipment. Current transducers and switches are also used to ensure motor protection and facilitate equipment maintenance procedures. Current transducers are also installed on cutting tools to diagnose the tool’s effectiveness. The same technique is used to monitor equipment that supplies heat to manufactured products, storage systems, or recirculating material. Relays are typically used to start loads, and pressure switches or zero-speed switches are used to monitor them. In September 1878, when Thomas Edison announced his intention to harness Niagara Falls and produce a safe, electric light system, gas stocks plummeted on Wall Street. Engineer James Eads tamed the mighty Mississippi, turning New Orleans into the second largest port in the nation. Football coach Knute Rockne of Notre Dame was a pivotal figure in the sudden rise of sports to a position of power in American culture. With data compiled from tens of thousands of sex questionnaires, Alfred Kinsey changed America's views about sex with the Kinsey Reports.
The tale of oil-seeking mavericks whose risk-taking, sweat and dreams changed an American industry.
An African American minister whose dream of ending racism galvanized millions of Americans in the civil rights movement. The historic journey of Apollo 8 captivated the world in 1968 -- a bright spot in a year marked by political assassinations, race riots, and the Vietnam War. Probably 80% of all testing performed in electrical power systems is related to the verification of insulation quality. Most electrical equipment in utility, industrial, and commercial power systems uses either 50Hz or 60Hz alternating current. Insulation may be simply modeled as a capacitor in parallel with a resistor as shown in Figure 1.
The result is an energy that is supplied to realign the molecules much like force will realign a network of rubber bands. Like Ic, Ida usually dies off fairly quickly as the molecules realign to their maximum extent.
In bad insulation the leakage current may be fairly large and it may actually increase with time.
If you think about Polarization Index, which is the ratio of DC insulation resistance between 1 minute and 10 minutes, the insulation system for most electrical equipment will exhibit changes in Ida well into minutes. Electrical Corner StoreCheck out our new #Electrical Corner Store with selected Electrician's Books, Testing and Safety equipment and other electrician's stuff!
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This could be dangerous or damaging to your electronics if you had a lot of charge stored in capacitors in your circuit.


When used to feed an electric power grid, an alternator must always operate at a constant speed that is precisely synchronized to the electrical frequency of the power grid. Since the rotor field only requires a tiny fraction of the power generated by the machine, the brushes for the field contact can be relatively small.
You are right, long threads are not often read, but neither are ones that have a quite technical topic described in a technical way without any context. As we go across to the right, the green line moves upwards - meaning the VOLTS are getting bigger in the positive direction.
I am an electrical and computer technician, so you are right, I do write like a technician, and I will have a tough time fixing that. It is called Alternating Current because our power alternates its polarity 60 times per second.
Might this be a case of "dirty" DC, which messes up my VTx (I got no ferrite rings, capasitors or anything to filter any noise)?Whats the best way to get rid of the interferance? The current conductor passes through a magnetically permeable core that concentrates the conductor’s magnetic field.
The current conductor passes through the core that magnifies the conductor’s magnetic field. The conventional approach to this monitoring problem has been to use pressure switches, optical sensors, and zero-speed switches.
Seeing load changes instantly can help you improve throughput, reduce waste, and prevent catastrophic equipment failure. Measuring power input can help improve efficiency, safeguard personnel, and reduce motor maintenance costs in a wide range of factory applications.
This output must be conditioned by a separate transducer into a process signal such as 4-20mA or a contact closure. Both sides of the shunt resistor are at line voltage, which in practice means bringing 480 VAC into an otherwise low-voltage control panel. Although it is in fact a low-cost device, the signal conditioner must be built to withstand 480 VAC and is very expensive.
Hall effect and induction use different techniques to measure the magnetic field around a current-carrying conductor. Both technologies measure this magnetic field, but with different sensing methods (see Figure 1). Because they tend to be more expensive than shunts or inductive transducers, their use is generally limited to measuring DC power.
The current conductor passes through a magnetically permeable core that magnifies the conductor’s magnetic field. The secondary current is converted to a voltage and conditioned to output process-level signals such as 4-20mA or contact closures. A well-designed inductive sensor can be configured as a two-wire device to reduce installation cost. Current transducers convert monitored current to a proportional AC or DC voltage or milliamp signal. To calculate the RMS current of a pure sine wave, the transducers simply divide the peak current by the square root of 2 (1.1414). The simulated wave can exhibit peaks several times greater than the average current, and their relative sizes change with the carrier and output frequency.
True RMS instruments measure the power or heating value of any current or voltage waveform. Designed for monitoring and switching AC and DC circuits, current-operated switches integrate current sensing and signal conditioning with a limit alarm. Newer designs provide field-adjustable set points with a potentiometer and LED or LCD feedback. Because current draw is such an excellent indicator of motor condition, the current sensor can be used to solve a wide range of process control, safety, and maintenance problems.
The output signal is used for closed-loop control between the crusher and the feed mechanism. Here the objective is to start a second motor only after the first motor is running and driving its load. Often they are used to replace auxiliary contacts, which signal only the contactor position.
These microprocessor-based devices feature built-in programmable timers that compensate for short-duration abnormalities and motor in-rush during startup.
In wastewater applications, organic matter can jam pumps and cause damage to both the motor and the pump before thermal overloads are tripped.
Today’s smaller control panels and crowded switchgear are driving the demand for more compact units with higher ratings and more versatile mounting options. This approach requires two installations and multiple conduit runs that increase the complexity of the system. At that time there were 121 Edison power stations scattered across the United States delivering DC electricity to its customers. Lee, the leading Confederate general of the American Civil War, remains a source of fascination and, for some, veneration.
This technical article briefly describes the fundamental concepts of insulation testing including – insulation behavior, types of tests, and some test procedures.
Because of this, the use of an alternating current source to test insulation would appear to be the logical choice. The current flow that results will comprise two components: the capacitive current (Ic) and the resistive current (Ir). The positive side of the molecules are attracted to the negative conductor and the negative side of the molecules are attracted to the positive conductor. Highly specialized for design of LV high power busbar trunking (<6300A) in power substations, buildings and industry fascilities.
This article gives the impression that this transient is over (It = Ir) in about 10 seconds, but I wish to point out that it continues on for much longer. Bender eliminates that problem by adapting the injected DC voltage (very slow pulse) to the existing (extraneous) DC voltage in the system.
You can either send us article in MS Word by email (and we will publisg it in your name) or write it by your own.
Every day, the generation and usage of energy produces more pollution than any other single industry. 60 vdc (60 volts in a direct current) is (in respect to time) a straight line +60 volts above the 0 volt level.
A DC generator can operate at any speed within mechanical limits, but always outputs direct current.
In the case of a brushless exciter, no brushes are used at all and the rotor shaft carries rectifiers to excite the main field winding.
They hit +120 (120 volts positive) then they come back down to 0 again and keep going until they get to -120 (negative 120 volts). That is all great and there are some very good reasons why AC is used to supply your house with power. I mainly wanted people to know about DC, AC is discussed so you have another type of current as a reference to compare it to, it helps to understand the time part of DC. In fact it would be very happy to run on a 3-phase AC current with a sinusoidal waveform like that of industrial 3-phase AC (household AC is single-phase), so long as the phases were synchronized to the rotor position. The problem got solved when I introduced a separate battery to power the VTx, 2s 800mAh or 3s 1000mAh, both work just fine. I would very much like to use a single battery to power everything for simplicity reasons, but even if there is a way to filter the noise, or whatever is causing this, would it be a safer bet to use a separate battery? Alternating current flows back and forth, rapidly switching direction many times per second. The Hall effect device is mounted in the core at a right angle to the concentrated magnetic field.
AC current constantly changes potential from positive to negative and back again, generally at the rate of 50 or 60 Hz. Within the past 10 years, however, a growing number of design and process engineers have found current sensing to be a more reliable and economical way to monitor and control electrically powered loads. Continuous real-time monitoring of current draw can also be used for trend analysis or status alarming. This photo was shot from an overhead crane at National Fuel Gas’s natural gas compressor station in Ellisburg, Pennsylvania. The Hall effect sensor is best suited to DC current, and the inductive sensor to AC current.
The Hall effect device is carefully mounted in a small slit in the core, at a right angle to the concentrated magnetic field. Hall effect transducers require more energy than conventional loop-powered, two-wire systems. These compact, self-powered devices provide field-adjustable set points and built-in mounting brackets to simplify installation.


AC current constantly changes potential from positive to negative and back again, generally at the rate of 50 Hz or 60 Hz. Inductive sensing provides both high accuracy and wide turndown, and the output signal is inherently isolated from the monitored voltage. And switching power supplies are small, efficient, and compact devices that are easily integrated with a wide variety of electrically powered equipment.
This method provides fast response (100·200 ms) at a moderate cost, but it works only on pure sine waves (see Figure 2). In these applications an average responding transducer can be accurate at 20 Hz, but 10% high at 30 Hz, and 10% low at 40 Hz. This allows very different waveforms to be compared to one another and to the equivalent DC (heating) value. The switch output is activated when the current level sensed by the limit alarm exceeds a user-selectable threshold. A drop in load signals the conveyor or loader to increase the feed rate, and a rise in load initiates a decrease in the feed rate. This type of safety interlock is used in a variety of commercial and industrial facilities. Most motors are equipped with local disconnect switches at the actual load to facilitate maintenance. In these operations, the current switch is more reliable because it is not subject to contact corrosion or set point drift, and does not require periodic maintenance or calibration.
A predictive maintenance schedule, based on the actual number of motor starts, ensures proper operation and reduces the risk of motor failure.
Signaling the operator that maintenance procedures are required reduces the production of rejected material and prevents process interruption. Alternatively, a blockage in the pump suction line can cause the pump to run dry, overheat, and damage seals. Today, modular relays can quick-connect to a wide range of current sensors from adjustable set point current switches to single-piece transducers.
Other smart devices feature user-programmable timers that compensate for short-duration abnormalities and motor start-up in-rush.
While "the Wizard of Menlo Park" and his staff would, in time, develop all the components needed for an electrical system -- bulbs, sockets, switches, wires, junction boxes, power meters, voltage regulators -- Edison himself became caught in a web of personal, patent, and corporate battles.
But DC had a great limitation -- namely, that power plants could only send DC electricity about a mile before the electricity began to lose power. A steam engine or some other outside source of motion moves the wire or armature through the magnetic field created by the magnets.In the example to the left, a loop of wire is spinning within a magnetic field. The current that flows through this new capacitor is called the dielectric absorption current (Ida) and will be explained later. The short burst of capacitive current flow may put a rather substantial stress on any test equipment that is applied to very large insulation systems such as cables or large rotating machine. This monitoring principle is patented under AMP (adapted monitoring pulse) by Bender Germany for the worldwide use. This AC electrical current is a sine wave that starts at 0 volts (point A), as it moves forward in time, it sweeps up to positive 120 volts, then sweeps down past 0 volts (point B) to negative 120 volts, then sweeps back up to 0 volts (point C).
You seem to know a lot about it, if you think it would help people to do that kind of post here, please feel free. Then they move back up towards the middle line and eventually hit 0, just where we started. But RC planes don't use AC current - they use a much simpler and easier to deal with form of current called Direct Current or DC. But when I just hook the main battery, the VTx transmits just black (its transmitting, but its just black screen, when I plug the power off it gives static).
So its the voltage, the 3s seems to be too much, though they say on Hobbyking that Tx works with up to 15 volt.
Solid-state current sensors are easier to install and more reliable than electromechanical devices–and they deliver more information. Installing this device requires cutting and re-terminating the current carrying conductor–an expensive and time-consuming proposition. This isolation ensures personnel safety and creates an almost imperceptible insertion loss (voltage drop) on the monitored circuit.
Inductive transducers are easier to install because they are two-wire, self-powered (0–5 VDC or 0–10 VDC outputs), or loop-powered (4-20mA output) instruments. Average responding transducers simply cannot provide an accurate measure of these distorted waveforms. For relay logic systems, switches should be equipped with integral time delays to allow for start-up surge and momentary sags or swells.
In this operation, controlling the feed rate helps prevent jamming, improves the uniformity or structure of the ground product, and enhances the efficiency of subsequent processing operations. If equipment is taken out of service at the disconnect, the contactor’s auxiliary contact will give a false on indication that can have serious safety or operational consequences.
Installing a current switch on the motor lead, and using the signal to run a counter or feed into an automated system, provides an accurate count of motor starts.
Installing a current transducer on one leg of the motor leads allows the operator to monitor both overload and underload conditions and take corrective action before the equipment is compromised. These enhanced control capabilities, higher ratings, and solid-state reliability have led to wider acceptance of current sensing technology as a replacement for conventional instrumentation.
In the end, Thomas Edison revolutionized the world, yet lost control of the industry that he founded. So when George Westinghouse introduced his system based on high-voltage alternating current (AC), which could carry electricity hundreds of miles with little loss of power, people naturally took notice. The reason it does is because of the resistance created by your thumb.It works much the same way for a light bulb. This is one cycle of this wave, power from the wall does this 60 times per second, hence 60 Hz is its frequency. Everyone is not in the some boat as you, but believe me, I'm happy for you that you did not need it. You are not the first one to notice this, I may appear angry sometimes, but I am not, I have very thick skin and try to take all criticism as constructive. When the energized Hall device is exposed to a magnetic field from the core, it produces a potential difference (voltage) that can be measured and amplified into process level signals such as 4-20mA or a contact closure. This secondary current is converted to a voltage and conditioned to output process-level signals such as 4-20mA or contact closures. Furthermore, because the shunt is a fixed voltage drop (insertion impedance) in the monitored circuit, it generates heat and wastes energy. Hall effect transducers are generally four-wire devices and require a separate power supply.
Understanding the two principal methods of amp measurement can help you specify the right device for these demanding applications. They are self-powered and consequently are a good choice for retrofits, renovations, and temporary monitoring (see Photo 1). This information can be used to schedule preventive maintenance and reduce costly emergency repairs.
In other words, a transformer can take a low-voltage current and make it a high-voltage current, and vice versa.This comes in handy in transmitting electricity over long distances.
Any fluxuations in the voltage or current causes the wave to become imperfect, bumpy, spiky, or dirty. It is alternating between +120 volts and -120 volts, swinging back and forth as time goes on. It produces 3 separate waves (one for each wire to the motor.) the speed of the motor has nothing to do with voltage or amps, but instead the timing of the current fed into it. The shunt is suitable only for DC current measurement and low-frequency AC measurement (<100 Hz). Because both types can be connected directly to data systems and display devices, they are ideal for monitoring motors, pumps, conveyors, machine tools, and any electrical load that requires an analog representation over a wide range of currents. By increasing and decreasing the wave length (frequency) of the trapezoidal wave on the 3 phases, the ESC causes the motor to spin faster and slower.
Their high power requirements preclude a self-powered design, and a separate power source requirement increases their installation cost.
Answer: The compressor in your refrigerator turning off and on, in fact anything anywhere that is hooked to your power grid turning off and on, and even lightning strikes during storms and problems at the power company.
Normally, because of the way noise is generated, some of it is generated at curtain frequencies. That is why when we swop any two motor wires, we reverse two of the phases, and that changes the direction of the motor?



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