Fuse .ps



Fuse 200?A Industrial fuse. 80?kA breaking capacity.Electronic symbols for a fuse. IEC (upper) and American (lower two) versions.In electronics and electrical engineering a fuse (short for fusible link) is a type of overcurrent protection device. Its typical component is a metal wire or strip (element) that melts when too much current flows, which interrupts (disconnects) the circuit in which it is connected. Circuit or device failure is often a reason for excessive current. A fuse blows (interrupts excessive current) so that further damage (ie. fire) is prevented. A fuse typically is not intended to protect from the initial cause of overcurrent.Overcurrent protection devices are an essential part of appliances and of power distribution systems to limit both threats to human life and damage. For example, too much current for too long may cause a wire to overheat, be damaged, or even start a fire. Wiring regulations often define a maximum fuse current rating. Fuses are selected to allow passage of normal current and of excessive current for short periods. And to interrupt what is called a short circuit, overload condition, or fault current.A fuse was patented by Thomas Edison in 1890 [1] as part of his successful electric distribution system. Edison writes, "The passage of an abnormal electric current fuses the safety-catch and breaks the circuit, as will be understood."Contents1 Characteristic parameters 2 Markings 2.1 Approvals 2.2 UK domestic fuses and their markings 3 Packages 3.1 Materials 3.2 Dimensions 3.3 Special features 4 Automotive fuses 4.1 Blade type 4.1.1 Color-coding 4.2 Bosch type 4.3 Lucas type 5 High voltage fuses 6 Fuses compared with circuit breakers 7 Fuse Boxes 8 British plug fuse 9 Coordination of fuses in series 10 Other fuse types 10.1 Resettable fuses 10.2 Thermal fuses Characteristic parametersRated current IN A maximum current that the fuse can continuously conduct without interruption to the circuit, or harmful effects on its surroundings. A fuse is derated 25% when selected. For example a 10 amp fuse is typically used for loads of up to 7.5 amps.Speed The speed at which a fuse blows depends on how much current flows through it and the material of which the fuse is made.Fuses are often characterized as "fast-blow", "slow-blow" or "time-delay", according to time required to respond to an overcurrent condition. Fuse selection depends on the load's characteristics. Details provided in I2t charts in manufacturer datasheets.Semiconductor devices may use a fast or ultrafast fuse since circuit board conductors may have little capacity to withstand the resulting overcurrent after a semiconductor fails. Fuses applied on motor circuits may have a time-delay characteristic, since the initial current surge during startup soon decreases and is harmless to wiring and the motor.The I2t value A measure of energy required to blow the fuse element relates actual current to time that a fuse actually blows (clears or disconnects). For example, 1.5 amps through a one amp fuse may take 45 seconds. Same fuse may blow after 3 amps for 2 seconds or 6 amps for 100 milliseconds. That same 1 amp fuse might conduct 2 amps for 2 seconds and remain conductive.These characteristics vary for each fuse family. Ballpark numbers suggests a standard fuse may require twice its rated current to open in one second. A fast-blow fuse may require twice its rated current to blow in 0.1 seconds. And a slow-blow fuse may require twice its rated current for tens of seconds to blow. Unique I2t parameters are provided by charts in manufacturer datasheets for each fuse family.Voltage drop A voltage drop across the fuse is usually provided by its manufacturer. Resistance may change when a fuse becomes hot due to energy dissipation while conducting higher currents. This resulting voltage drop should be taken into account particularly when using a fuse in low-voltage applications. Voltage drop often is not significant in more traditional wire type fuses. But can be significant in other technologies such as resettable fuse (PPTC) type fuses.Breaking capacity The breaking capacity is a maximum current that can safely be interrupted by the fuse. Generally this should be higher than the prospective short circuit current. Miniature fuses may have an interrupting rating only 10 times their rated current. Some fuses are designated High Rupture Capacity (HRC) and are usually filled with sand or a similar material. Fuses for small low-voltage (ie residential) wiring systems are commonly rated to interrupt 10,000 amperes. Fuses for larger power systems must have higher interrupting ratings, with some low-voltage current-limiting HRC fuses rated for 300,000 amperes. Fuses for high-voltage equipment, up to 115,000 volts, are rated by the total apparent power (megavolt-amperes, MVA) of the fault level on the circuit.Rated voltage Voltage rating of the fuse must be greater than or equal to what would become the open circuit voltage. For example, a glass tube fuse rated at 32 volts (a 0.25 inch diameter by 1.25 inch fuse typically found in older automobiles) would not reliably interrupt current from a voltage source of 120 or 230 volts. Fuses carrying a 250 V rating may be safely used in a 125 V circuit. If a 32 volt fuse attempts to interrupt the 120 or 230 volt source, an arc may result. Plasma inside that glass tube fuse may continue to conduct current until current eventually so diminishes that plasma reverts to an insulating gas. Rated voltage should be larger than the maximum voltage source it would have to disconnect. This requirement applies to every type of fuse.Rated voltage remains same for any one fuse even when similar fuses are connected in series. Connecting fuses in series does not increase a resulting rated voltage.Medium-voltage fuses rated for a few thousand volts are never used on low voltage circuits, due to their expense and because they cannot properly clear the circuit when operating at very low voltages.Temperature Rerating Ambient temperature will change a fuse's operational parameters. A fuse rated for 1 amp at 25°C may conduct up to 10% or 20% more current at -40°C and may open at 80% of its rated value at 100°C. Of course, rerating values will vary with each fuse family and are provided in manufacturer datasheets.MarkingsA sample of the many markings that can be found on a fuse.Most fuses are marked on the body or end caps with markings that indicate their ratings. Surface mount technology "chip type" fuses feature few or no markings, making identification very difficult.When replacing a fuse, it is important to interpret these markings correctly as fuses that may look the same could be designed for very different applications. Fuse markings[2] will generally convey the following information;Ampere rating of the fuse Voltage rating of the fuse Time-current characteristic ie. element speed Approvals Manufacturer / Part Number / Series Breaking capacity ApprovalsThe majority of fuse manufacturers build products that comply with a set of guidelines and standards, based upon the application of the fuse. These requirements are devised by many different Government agencies and certification authorities. Once a fuse has been tested and proven to meet the required standard, it may then carry the approval marking of the certifying agency.UK domestic fuses and their markingsThere are generally two sizes of modern domestic fuse found in the UK. The first is the standard plug top fuse which measures 1 inch (25mm) long by 1/4 inch (6.3mm) in diameter. The second is a smaller fuse which is generally found inside modern electrical equipment, and measures 20mm long by 5mm in diameter.The performance of both types of fuse is governed by the characteristic parameters (mentioned above), which can be identified from the markings on the side of the fuse.Speed The first marked parameter is the speed with which the fuse blows. The fastest blowing fuses are designated "FF" (or flipping fast!), these are designed for the most sensitive electrical equipment where even a short exposure to an overload current could be very damaging. Next on the scale are normal fast blow fuses designated simply "F", these are the most general purpose fuses and are very widely used in applications where the ultra fast blow speed of "FF" fuses is not required. The next type of blow speed is the time delay fuse (also known as anti-surge, or slow-blow), designated "T". Time delay fuses are designed to allow a current which is above the rated value of the fuse to flow for a short period of time without the fuse blowing. These types of fuse are used on equipment which draw a large initial current for a few milliseconds after they have been switched on.Rated current The second marked parameter is the rated current of the fuse. This is simply the maximum current that will be allowed to flow through the fuse before it blows. This will be written in either Amps (A) or milliamps (mA) on the side of the fuse.Breaking capacity The third marked parameter is the breaking capacity, or the potential maximum current the fuse can withstand without shattering. There are two types of fuse in this case, High Blow Current (HBC) and Low Blow Current (LBC). HBC fuses (sometimes known as HRC or High Rupture Current) are generally defined as being able to withstand more than 10 times their rated current without shattering. They typically have a ceramic body and are filled with sand. UK plug fuses are HBC fuses. HBC fuses are designated "H". LBC fuses on the other hand are designed for situations where the maximum fault current is likely to be less than 10 times the rated fuse current. They typically have a glass body in which the fuse wire can clearly be seen, making it very easy to see if the fuse has blown. LBC fuses are designated "L".Rated voltage The fourth marked parameter is the rated voltage of the fuse. In the UK domestic fuse, this will generally be 240/250V.These attributes are marked on the side of the fuse, in the order presented here. So for example a fuse which has "F500mAL250V" written on the side is a fast blow fuse rated to 500 milliamps and is an LBC fuse designed for circuits with a smaller maximum fault current and running at 250 Volts, and a fuse with "T5AH250V" written on the side is a time delay fuse rated to 5 Amps and is HBC and rated to 250 Volts.PackagesFuses come in a vast array of sizes & styles to cater for the immense number of applications in which they are used. While many are manufactured in standardised package layouts to make them easily interchangeable, a large number of new styles are released into the marketplace every year. Fuse bodies may be made of ceramic, glass, plastic, fiberglass, Molded Mica Laminates, or molded compressed fibre depending on application and voltage class.Cartridge (ferrule) fuses have a cylindrical body terminated with metal end caps. Some cartridge fuses are manufactured with end caps of different sizes to prevent accidental insertion of the wrong fuse rating in a holder. An example of such a fuse range is the 'bottle fuse', which in appearance resembles the shape of a bottle.Fuses designed for soldering to a printed circuit board have radial or axial wire leads. Surface mount fuses have solder pads instead of leads.Fuses used in circuits rated 200-600 volts and between about 10 and several thousand amperes, as used for industrial applications such as protection of electric motors, commonly have metal blades located on each end of the fuse. Fuses may be held by a spring loaded clip or the blades may be held by screws. Blade type fuses often require the use of a special purpose extractor tool to remove them from the fuse holder.Semi-enclosed fuses are fuse wire carriers in which the fusible wire itself can be replaced. These are used in consumer units in some parts of the world, but are becoming less common.[edit] MaterialsWhile glass fuses have the advantage of a fuse element visible for inspection purposes, they have a low breaking capacity which generally restricts them to applications of 15 A or less at 250 VAC. Ceramic fuses have the advantage of a higher breaking capacity facilitating their use in higher voltage/ampere circuits. Filling a fuse body with sand provides additional protection against arcing in an overcurrent situation.DimensionsCartridge fuses are generally measured as the overall length and diameter of the fuse. Due to the large variety of cartridge fuses available, fuse identification relies on accurate measurements as fuses can differ by only a few millimeters between types. 'Bottle style' cartridge fuses also require the measurement of the cap diameter as this varies between ampere ratings.Other fuse packages can require a variety of measurements such as;body (width x height x depth) blade or tag (width x height x depth) overall length of the fuse (when the fuse features blades or tags) overall width of the fuse (when the fuse features 2 bodies) width of the mounting holes (when the fuse features tags) distance between blades (when radially configured) fixing centre (when the fuse features tags - see below) Fuses fitted with tags require the fixing centre measurement. This measurement is the distance between the tag mounting holes on either end of the fuse as measured from the centre of each mounting hole.Special featuresGlass cartridge and plug fuses allow direct inspection of the fusible element. Other fuses have other indication methods including:Indicating pin or striker pin: extends out of the fuse cap when the element is blown. Indicating disc: a coloured disc (flush mounted in the end cap of the fuse) falls out when the element is blown. Element window: a small window built into the fuse body to provide visual indication of a blown element. Flag: an external sprung arm that is released to an extended position once the element is blown. External trip indicator: similar function to striker pin, but can be externally attached (using clips) to a compatible fuse. Some fuses allow a special purpose microswitch or relay unit to be fixed to the fuse body. When the fuse element blows, the indicating pin extends to activate the micro switch or relay which in turn triggers an event. Color-codingBlade fuses use a color-coding standard. [6] The Mini (ATM) and ATO style fuses use the same color-coding system, while the larger maxi fuses use a different system, with only some colors representing the same current ratings.Mini, Low-Profile Mini, and ATO Color-coding:ColorCurrent (A)black*1grey2violet3pink4orange/tan5brown7.5red10aqua/blue15yellow20clear/natural25green30blue green*35amber*40Maxi Color-coding:ColorCurrent (A)yellow20grey25green30brown35orange40red50blue/aqua60tan70clear/natural80Bosch typeBosch type fuse (used in older cars)Bosch type fuses (also known as torpedo type fuses) are used in old (often European) automobiles. The physical dimension of this type of fuse is 6x25 mm with conical ends. Bosch type fuses usually use the same color coding for the rated current. The DIN standard is 72581/1. The size of the fuse is: 6x25 mm.ColorAmpereyellow5Awhite8Ared16Ablue25Agrey40ALucas typeLucas type fuses are used in old British made or assembled automobiles. The physical length of this type of fuse is either 1" or 1.25" with conical ends. Lucas type fuses usually use the same color coding for the rated current. Lucas fuses have three ratings; the continuous current they are designed to carry, the instantaneous current at which they will fuse, and the continuous current at which they will also fuse. The figure found on Lucas fuses is the continuous fusing current which is twice the continuous amp rating that the system should be using; this can be a source of confusion when replacing Lucas fuses with non Lucas fuses. High voltage fusesA set of pole-top fusible cutouts with one fuse blown, protecting a transformer- the white tube on the left is hanging downFuses are used on power systems up to 115,000 volts AC. High-voltage fuses are used to protect instrument transformers used for electricity metering, or for small power transformers where the expense of a circuit breaker is not warranted. For example, in distribution systems, a power fuse may be used to protect a transformer serving 1-3 houses. A circuit breaker at 115 kV may cost up to five times as much as a set of power fuses, so the resulting saving can be tens of thousands of dollars. Pole-mounted distribution transformers are nearly always protected by a fusible cutout, which can have the fuse element replaced using live-line maintenance tools.Large power fuses use fusible elements made of silver, copper or tin to provide stable and predictable performance. High voltage expulsion fuses surround the fusible link with gas-evolving substances, such as boric acid. When the fuse blows, heat from the arc causes the boric acid to evolve large volumes of gases. The associated high pressure (often greater than 100 atmospheres) and cooling gases rapidly extinguish (quench) the resulting arc. The hot gases are then explosively expelled out of the end(s) of the fuse. Other special High Rupturing Capacity (HRC) fuses surround one or more parallel connected fusible links with an energy absorbing material, typically silicon dioxide sand. When the fusible link blows, the sand absorbs energy from the arc, rapidly quenching it, creating an artificial fulgurite in the process.A 115 kV high-voltage fuse in a substation near a hydroelectric power plantFuses compared with circuit breakersFuses have the advantages of often being less costly and simpler than a circuit breaker for similar ratings. The blown fuse must be replaced with a new device which is less convenient than simply resetting a breaker and therefore likely to discourage people from ignoring faults. On the other hand, replacing a fuse without isolating the circuit first (most building wiring designs do not provide individual isolation switches for each fuse) can be dangerous in itself, particularly if the fault is a short circuit.High rupturing capacity fuses can be rated to safely interrupt up to 300,000 amperes at 600 V AC. Special current-limiting fuses are applied ahead of some molded-case breakers to protect the breakers in low-voltage power circuits with high short-circuit levels."Current-limiting" fuses operate so quickly that they limit the total "let-through" energy that passes into the circuit, helping to protect downstream equipment from damage. These fuses clear the fault in less than one cycle of the AC power frequency. Circuit breakers cannot offer similar rapid protection.Some types of circuit breakers must be maintained on a regular basis to ensure their mechanical operation during an interruption. This is not the case with fuses, in which no mechanical operation is required for the fuse to operate under fault conditions.In a multi-phase power circuit, if only one fuse opens, the remaining phases will have higher than normal currents, and unbalanced voltages, with possible damage to motors. Fuses only sense overcurrent, or to a degree, over-temperature, and cannot usually be used independently with protective relaying to provide more advanced protective functions, for example, ground fault detection.Some manufacturers of medium-voltage distribution fuses combine the overcurrent protection characteristics of the fusible element with the flexibility of relay protection by adding a pyrotechnic device to the fuse operated by external protection relays.Fuse Boxesrewirable fusesMEM rewirable fuse boxMEM rewirable fuse holders (30A & 15A)Wylex fuse boxfuse wire as sold to UK consumersIn the UK, older electrical consumer units (also called fuse boxes) are fitted either with semi-enclosed (rewirable) fuses (BS 3036) or cartridge fuses (BS 1361). (Fuse wire is commonly supplied to consumers as short lengths of 5A-, 15A- and 30A-rated wire wound on a piece of cardboard.) Modern consumer units usually contain miniature circuit breakers (MCBs) instead of fuses, though cartridge fuses are sometimes still used, as MCBs are rather prone to nuisance tripping.Renewable fuses (rewirable or cartridge) allow user replacement, but this can be hazardous as it is easy to put a higher-rated or double fuse element (link or wire) into the holder (“overfusing”), or simply fitting it with copper wire or even a totally different type of conducting object (hairpins, paper clips, nails etc.) to the existing carrier. Such tampering will not be visible without full inspection of the fuse. Fuse wire was never used in North America for this reason, although renewable fuses continue to be made for distribution boards.The fuse boxes pictured in this section are (right) a MEM consumer unit with four rewirable fuse holders (two 30A & two 15A) installed c.1957 (cover removed); a “Wylex standard” unit with eight rewirable fuse holders.The “Wylex standard” consumer unit was very popular in the United Kingdom until the wiring regulations started demanding Residual-Current Devices (RCDs) for sockets that could feasibly supply equipment outside the equipotential zone. The design does not allow for fitting of RCDs or RCBOs. Some Wylex standard models were made with an RCD instead of the main switch, but (for consumer units supplying the entire installation) this is no longer compliant with the wiring regulations as alarm systems should not be RCD-protected. There are two styles of fuse base that can be screwed into these units — one designed for rewirable fusewire carriers and one designed for cartridge fuse carriers. Over the years MCBs have been made for both styles of base. In both cases, higher rated carriers had wider pins, so a carrier couldn't be changed for a higher rated one without also changing the base. Cartridge fuse carriers are also now available for DIN-rail enclosures.[7]In North America, fuses were used in buildings wired before 1960. These "Edison Base" type fuses, would screw into a fuse socket similar to Edison-base incandescent lamps. Ratings were 5, 10, 15, 20, 25, and 30 amperes. To prevent installation of fuses with an excessive current rating, later fuse boxes included rejection features in the fuseholder socket. Some installations use resettable miniature thermal circuit breakers which screw into that fuse socket.One form of fuse box abuse was to put a penny in the socket, which defeated overcurrent protection and resulted in a dangerous condition.In the 1950s, fuses in new residential or industrial construction for branch circuit protection were superseded by low voltage circuit breakers.British plug fuse20?mm 200?mA glass cartridge fuse used inside equipment and 1?inch 13?A ceramic British plug fuse.The BS 1363 13?A plug has a BS 1362 cartridge fuse inside. This allows the use of 30?A/32?A (30?A was the original size; 32?A is the closest European harmonised size) socket circuits safely. In order to keep cable sizes manageable these are usually wired in ring mains. It also provides better protection for small appliances with thin flex as a variety of fuse ratings (1?A, 2?A, 3?A, 5?A, 7?A, 10?A 13?A with 3, 5 and 13 being the most common) are available and a suitable fuse should be fitted to allow the normal operating current while protecting the appliance and its cord as well as possible. With some loads it is normal to use a slightly higher rated fuse than the normal operating current. For example on 500 W halogen floodlights it is normal to use a 5?A fuse even though a 3?A would carry the normal operating current. This is because halogen lights draw a significant surge of current at switch on as their cold resistance is far lower than their resistance at operating temperature.In most other wiring practices the wires in a flexible cord are considered to be protected by the branch circuit overcurrent device, usually rated at around 15 amperes, so a plug-mounted fuse is not used. Small electronic apparatus often includes a fuseholder on or in the equipment, to protect internal components only.The rating on a BS1362 fuse specifies the maximum current the fuse can pass 'indefinitely' under standard conditions. The fuse will pass higher currents than the rated value for significant periods, depending on how high the overload is. Fuse manufacturers publish tables or graphs of fuse characteristics to allow electrical system designers to specify the correct fuse for the conditions under which it will be expected to operate. One example is the table published by Cooper-Bussmann for their BS1362 fuses[8]. In this table it can be seen that the fuse is specified to be able to carry its rated current for a minimum of 1,000 hours; 1.6 times its rated current for a minimum of 30 minutes; and 1.9 times its rated current for a maximum of 30 minutes. Thus, this BS1362 13A fuse is only rated to break its circuit after carrying 24.7 Amps for 30 minutes.Coordination of fuses in seriesWhere several fuses are connected in series at the various levels of a power distribution system, it is desirable to blow (clear) only the fuse (or other overcurrent device) electrically closest to the fault. This process is called "coordination" and may require the time-current characteristics of two fuses to be plotted on a common current basis. Fuses are selected so that the minor, branch, fuse disconnects its circuit well before the supplying, major, fuse starts to melt. In this way, only the faulty circuit is interrupted with minimal disturbance to other circuits fed by a common supplying fuse.Where the fuses in a system are of similar types, simple rule-of-thumb ratios between ratings of the fuse closest to the load and the next fuse towards the source can be used.Other fuse typesResettable fusesSo-called "self-resetting" fuses use a thermoplastic conductive element known as a Polymeric Positive Temperature Coefficient (or PPTC) thermistor that impedes the circuit during an overcurrent condition (by increasing device resistance). The PPTC thermistor is self-resetting in that when current is removed, the device will cool and revert back to low resistance. These devices are often used in aerospace/nuclear applications where replacement is difficult, or on a computer motherboard so that a shorted mouse or keyboard does not cause motherboard damage.Thermal fusesA "thermal fuse" is often found in consumer equipment such as coffee makers or hair dryers or transformers powering small consumer electronics devices. They contain a fusible, temperature-sensitive alloy which holds a spring contact mechanism normally closed. When the surrounding temperature gets too high, the alloy melts and allows the spring contact mechanism to break the circuit. The device can be used to prevent a fire in a hair dryer for example, by cutting off the power supply to the heater elements when the air flow is interrupted (e.g. the blower motor stops or the air intake becomes accidentally blocked). Thermal fuses are a 'one shot', non-resettable device which must be replaced once they have been activated (blown).Low Voltage HRC Fuse High Voltage HRC FusesDescription : High Voltage HRC Fuses as per BS:2692 DIN 43625, IEC:282 for protection of Motors Distribution Transformers, Capacitors, Cables, Voltage Transformers are available for both Air and Oil applications. They are available from 3.6kV upto 36kV Class. Striker pins of heavy, medium and spring operated types are provided in specific rating for appropriate applications.CT –current transformerDesigning, installing, and maintaining a voltmeter capable of directly measuring 13,800 volts AC would be no easy task. The safety hazard alone of bringing 13.8 kV conductors into an instrument panel would be severe, not to mention the design of the voltmeter itself. However, by using a precision step-down transformer, we can reduce the 13.8 kV down to a safe level of voltage at a constant ratio, and isolate it from the instrument connections, adding an additional level of safety to the metering system: Now the voltmeter reads a precise fraction, or ratio, of the actual system voltage, its scale set to read as though it were measuring the voltage directly. The transformer keeps the instrument voltage at a safe level and electrically isolates it from the power system, so there is no direct connection between the power lines and the instrument or instrument wiring. When used in this capacity, the transformer is called a Potential Transformer, or simply PT. Potential transformers are designed to provide as accurate a voltage step-down ratio as possible. To aid in precise voltage regulation, loading is kept to a minimum: the voltmeter is made to have high input impedance so as to draw as little current from the PT as possible. As you can see, a fuse has been connected in series with the PTs primary winding, for safety and ease of disconnecting the PT from the circuit. A standard secondary voltage for a PT is 120 volts AC, for full-rated power line voltage. The standard voltmeter range to accompany a PT is 150 volts, full-scale. PTs with custom winding ratios can be manufactured to suit any application. This lends itself well to industry standardization of the actual voltmeter instruments themselves, since the PT will be sized to step the system voltage down to this standard instrument level. Following the same line of thinking, we can use a transformer to step down current through a power line so that we are able to safely and easily measure high system currents with inexpensive ammeters. Of course, such a transformer would be connected in series with the power line, like this: Note that while the PT is a step-down device, the Current Transformer (or CT) is a step-up device (with respect to voltage), which is what is needed to step down the power line current. Quite often, CTs are built as donut-shaped devices through which the power line conductor is run, the power line itself acting as a single-turn primary winding: Some CTs are made to hinge open, allowing insertion around a power conductor without disturbing the conductor at all. The industry standard secondary current for a CT is a range of 0 to 5 amps AC. Like PTs, CTs can be made with custom winding ratios to fit almost any application. Because their "full load" secondary current is 5 amps, CT ratios are usually described in terms of full-load primary amps to 5 amps, like this: The "donut" CT shown in the photograph has a ratio of 50:5. That is, when the conductor through the center of the torus is carrying 50 amps of current (AC), there will be 5 amps of current induced in the CT's winding. Because CTs are designed to be powering ammeters, which are low-impedance loads, and they are wound as voltage step-up transformers, they should never, ever be operated with an open-circuited secondary winding. Failure to heed this warning will result in the CT producing extremely high secondary voltages, dangerous to equipment and personnel alike. To facilitate maintenance of ammeter instrumentation, short-circuiting switches are often installed in parallel with the CT's secondary winding, to be closed whenever the ammeter is removed for service: Though it may seem strange to intentionally short-circuit a power system component, it is perfectly proper and quite necessary when working with current transformers.Split Core Transformer -CTSplit Core CT Current Transformer Split core current transformers have interleaved joint and hinge structure.Split core CTs have a removable section, so that they can be installed without interrupting the circuit.A split core current transformer for coupling monitoring apparatus to a current carrying conductor includes a two-piece annular core structure formed by first and second arcuate core assemblies having windings, connectable to the monitoring apparatus, wound on laminated core sections, the laminated core sections each including a plurality of flat lamination elements arranged in a stacked configuration with alternate elements having generally circular end portions which project beyond the main body portion of the arcuate core section at each end thereof defining generally circular gaps, permitting interleaving of the projecting end portions of the core sections of the two core assemblies providing an annular core structure having two interleaved joints which are held together by way of removable hinge pins which permit separation of the interleaved projecting end portions at either one of the joints to facilitate coupling to the current carrying conductor.MSQ Current TransformersThis series of CT can be applied to test, control, display and record the running of the electrical equipment, and to protect the equipment against the damage, in the AC circuit with the rated voltage value below 720V and the frequency of 50-60Hz. The product can be also applied to form a complete set of mine transformer The products comply with VDE 0414, BS7626 and IEC 44-1 standard. Technical characteristics of current transformers: WITH BUSBARType Rated current (A) Rated power (VA) Weight (kg) Class:0.5 Class:1 MSQ-30B 5/510/515/520/525/530/540/550/560/575/580/5100/5120/5125/5150/5200/5250/5 5-105-105-105-105-105-105-105-105-105-105-105-105-105-105-105-105-10 5-105-105-105-105-105-105-105-105-105-105-105-105-105-105-105-105-10 0,600,600,600,600,600,600,600,600,600,600,600,600,600,600,600,600,60 Type Rated current(A) Rated power (VA) Weight (kg)Class:0.5 Class:1 MSQ-30T 100/5125/5150/5160/5200/5250/5 2.5-53-55-105-105-105-10 55-105-105-105-105-10 0,620,620,620,620,620,62 ? Technical characteristics of current transformers:WINDOWS TYPE WITH BUSBAR Bar: 30 X 10mm.conductor: ?20mm. Type Rated current (A) Rated power (VA) Weight (kg) Class:0.5 Class:1 MSQ-30B 30/540/550/560/575/580/5100/5150/5200/5250/5300/5 ----11.52.55-105-105-105-10 11111.52.555-105-105-105-10 0,40,40,40,40,40,40,40,40,40,40,4 WINDOWS TYPE Bar: 40 X 10mm.conductor: ?30mm. Type Rated current (A) Rated power (VA) Weight (kg) Class:0.5 Class:1 MSQ-40 100/5150/5200/5250/5300/5400/5500/5 2.5355-105-105-105-10 2.555-105-105-105-105-10 0,380,380,380,380,380,380,38 WINDOWS TYPE Bar: 60 X 20mm.conductor: ?40mm. Bar: 80 X 30mm.or 100 X 10mm.conductor:?60mm. WINDOWS TYPE Bar: 80 X 30mm.or 100 X 10mm.conductor:?60mm. Type Rated current (A) Rated power (VA) Weight (kg) Class:0.5 Class:1 MSQ-100 1500/51600/52000/52250/52500/53000/5 151515151515 151515151515 0,800,800,941,101,16 Technical characteristics of current transformers: WINDOWS TYPE WINDOWS TYPE Bar: 82 X 30mm.conductor: ?80mm.. Type Rated current (A) Rated power (VA) Weight (kg) Class:0.5 Class:1 MSQ-85 750/5800/51200/51500/5 1515151515 1515151515 0,750,820,890,991,02 WINDOWS TYPE Bar: 125 X 57mm. or 125 X 10mm.conductor: ?60mm. Type Rated current (A) Rated power (VA) Weight (kg) Class:0.5 Class:1 MSQ-125 1500/52000/52500/53000/54000/55000/5151515151515 303030303030 1,01,151,451,601,902,20 WINDOWS TYPE Bar: 125 X 38mm.. Type Rated current (A) Rated power (VA) Weight (kg) Class:0.5 Class:1 MSQ-100 800/5100/51200/51250/51500/51600/5 2000/52250/52500/53000/54000/55000/5 7.5101012.51515 151515151515 152025303030 3030 30 3030 30 1,01,01,01,01,0 1,051,151,201,451,60 1,902,20 Ring Type Oil Immersed Bushing Ct's1543685147955Mahendra Electrical Works is the established name in manufacturing of Bushing CT's for almost 3 decades. These Cts are used in distribution and power transformers upto 500MVA capacity and voltage class upto 400kv.Mahendra Electrical Works has been supplying bushing CT's to all major transformer manufacturers in India like CGL, EMCO, Alstom, Bharat Bijlee, Transformers and Rectifiers India Ltd., Asea Brown Boveri. All products of Mahendra Electrical Works have been approved by major consultants, electricity boards and railways.Features:Mounted inside the transformer tank It replaces the outdoor C.T. in the switchyard hence cost effective and maintenance free Used for protection of high value power transformers C.Ts. are manufactured in single as well as multi core, multi ratio This product is type tested by ERDA, Baroda.Application : Used in distribution & power transformers, for metering & protective applicationsOutdoor Oil cooled Current Transformer2018665339725-2374902590803366135228600General Information:Oil cooled transformers are made for use on various systems ranging from 11kv to 33kv. the basic construction of the CT is similar to CT of all voltage classes in that the core is placed in a tank mounted on top of the bushing and adequate paper insulation is provided on it. The secondary leads are run through the bushing to the secondary terminal box placed at the bottom of the bushing.The advantage of this type of construction is that the transformer is dynamically more stable under short circuit conditions, the various forces on the primary conductors tending to balance on another. Requisite number of the primary turn are put on the core and the two ends are bought out for connection into the system. The primary ends are terminated on the terminals 30 mm dia 80mm long for easy connection into the system.In the case of two ratio current transformer in which the different ratios are obtained by primary reconnection, four primary terminals are brought out on the tank(corresponding to the two primary windings) and these are connected in series or parallel, by connecting links provided depending upon the ratio required. The transformers are fully sealed in construction and are supplied filled with required quantity of oil. Adequate allowance is made for expansion of oil due to temperature variations and as such a breather is considered unnecessary.Since the transformer oil is never exposed to atmosphere the danger of its contamination is completely avoided. It is therefore not necessary to clean the oil during the life of the transformer. Oil fills and oil drains are, therefore not provided on the current transformers for voltages less than 132kv. For current transformers for 132 kv systems, oil fill and oil drain is provided but these are purely for manufacturing convinience and these are fully sealed before despatch.?This product is type tested at ERDA, BarodaTechnical information required for tenderingRatio Number of Cores VA Burden Accuracy Class Rated Short Time Current Rating Voltage Class System conditions LT Bar Primary CT in moulded caseLT Bar Primary Current Transformer in Moulded CaseFeatures: CT is housed in attractive & rigid ABS case(color as required) Easy to slip on busbars upto 40x12mm round conductors upto 35mm 5 types of mounting arrangement available Secondary Terminal sealing arrangement available(to avoid tampering) Type tested at ERDA, Baroda Application: Very useful for control panels and UPS Used for revenue metering Widely used by Electricity boards along with energy meters Specifications required for orderingRatio VA Burden Accuracy Class ? Round conductors upto 35 mmFlat bars upto 40 mm * 13 mmRatioRated VA burdenAccuracy class50/5A2.5375/5A53100/5A53100/5A31150/5A153150/5A7.51200/5A151200/5A50.5300/5A7.50.5300/5A51400/5A150.5500/5A150.5600-1000/5A300.5Secondary of 1A can be offered for all the ratios?LT Bar Primary Tape wound CTLT bar Primary Tape Insulated Current TransformerFeatures: Can be designed as per customers requirement to slip on busbars and cables of higher diameters available in RYB coloured tapes Customized mounting arrangements available Application: CTs for metering protective applications Specifications required for orderingRatio VA Burden Accuracy Class Standard Dimension for Tape Wound C.Ts.RatioApproximate Overall Dimensions in mmRated Burden VAAccuracy ClassABC50/5A30855055.050/5A30855055.075/5A30855055.0100/5A35865051.0150/5A35855051.0200/5A5011040101.0250/5A5010045101.0300/5A5010035101.0400/5A6010535151.0500/5A6010535151.0600/5A6010535151.0800/5A10514035151.01000/5A10514035151.01200/5A10514035151.01600/5A11516535151.01600/5A11516535151.02000/5A11616535151.02400/5A13019035151.02500/5A13019035151.03000/5A13019035151.0Tolerance for A, B, C is +/- 3mm ................
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