Presentation Applications Fuse range selection 0550N 05579N Public distribution Protection of motors Our Fusarc CF, Soléfuse, Tépéfuse and MGK fuses make up a broad, consistent and uniform range of high breaking capacity fuses and limiters. They are all of combined type and they are constructed so that they can be installed both indoors and outdoors (according to the type). Their main function is to protect medium distribution devices (from 3 to 3 kv) from both the dynamic and thermal effects of short circuit s greater than the fuse s minimum breaking. Considering their low cost and their lack of required maintenance, medium fuses are an excellent solution to protect various types of distribution devices: b medium consumers (transformers, motors, capacitors, etc.); b public and industrial electrical distribution networks. They offer dependable protection against major faults occuring either on medium or low circuits. This protection can be further enhanced by combining the fuses with low protection systems or an over relay. Selection table Depending on the equipment to be protected and its rating, the table below gives the range of fuses which are suited to the protection application. Voltage Motors Power transformers Capacitors Voltage transformers 3. Fusarc CF Fusarc CF Fusarc CF Fusarc CF MGK 7. Fusarc CF Fusarc CF Fusarc CF Fusarc CF MGK Soléfuse Soléfuse Fusarc CF Fusarc CF Fusarc CF Tépéfuse Soléfuse Soléfuse Fusarc CF 7.5 Fusarc CF Fusarc CF Tépéfuse Soléfuse Soléfuse Fusarc CF Fusarc CF Fusarc CF Tépéfuse Soléfuse Fusarc CF Soléfuse 3 Fusarc CF Fusarc CF Tépéfuse Soléfuse Soléfuse Fusarc CF Soléfuse (UTE standard; transformer protection) 0557N MGK (UTE standard; motor protection) Fusarc CF (DIN standard; transformer, motor and capacitor protection) Tépéfuse (UTE standard; transformer protection) Schneider Electric
Presentation Main characteristics 0553N Key characteristics The most significant features provided by our range of fuses are as follows: b high breaking capacity; b high limitation; b dependable interruption of critical s; b low breaking over; b low dissipated power; b no maintenance or ageing; b for indoor and outdoor; b with a striker for indication and tripping. Standards Our fuses are designed and manufactured according to the following standards: b IEC--, IEC-77 (Fusarc CF, Soléfuse,Tépéfuse, MGK); b DIN 35 (Fusarc CF); b VDE 070-0 (Fusarc CF); b UTE C00, C (Soléfuse, Tépéfuse). Quality assurance system In addition to being tested in our own laboratories, as well as in official laboratories such as the CESI, Les Renardiers and Labein, with their own respective certificates, our fuses are manufactured according to quality guidelines within the framework of the ISO-900 and ISO- quality system certification awarded by the AENOR (IQ-NET) which provides additional guarantees for customers. Testing During manufacture, each fuse is subject to systematic routine testing with the aim of checking its quality and conformity: b dimensional control and weight control; b visual control of markings, labelling and external appearance; b electrical resistance measurement: a key point to ensure that the fuses have the required performance levels at the end of the production process and to check that no damage has occured during assembly. Measurement of the room temperature resistance of each fuse is therefore carried out in order to check that they are in line with values according to their rated and rated. Furthermore we carry out internal type-testing on our fuses in order to comply with our quality policy. Seal testing: in order to test the sealing of our Fusarc CF fuses, they are plunged into a hot water bath (0 C) for 5 minutes, according to standard IEC -. Quality certified to ISO 900 and ISO A major advantage Within each of its production units, Schneider Electric integrates a functional organisation whose main mission is to check quality and monitor compliance with standards. MESA, the only company within Schneider that makes fuses, is certified by AENOR (the Spanish Standards Association), and is certified to ISO 900 and ISO (IQ-NET). Schneider Electric 3
Presentation Main characteristics MT000 Key definitions Un: rated This is the highest between phases (expressed in kv) for the network on which the fuse might be installed. In the medium range, the preferred rated s have been set at: 3. - 7. - - 7.5 - and 3 kv. In: rated This is the value that the fuse can withstand on a constant basis without abnormal temperature rise (generally 5 K for the contacts). Dependable operating range I3: minimum rated breaking This is the minimum value which causes the fuse to blow and break the. For our fuses, these values are of between 3 and 5 times the In value. Comment: it is not enough for a fuse to blow to interrupt the flow of. For values less than I3, the fuse will blow, but may not break. Arcing continues until an external event interrupts the. It is therefore essential to avoid using a fuse in the range between In and I3. I: critical s (s giving similar conditions to the maximum arc energy). The value of I varies between 0 and times the In value, depending on then design of the fuse element. If the fuse can break this, it can also break s between I3 and I. I: maximum rated breaking This is presumed fault that the fuse can interrupt. This value is very high for our fuses ranging from 0 to 3 ka. Comment: it is necessary to ensure that the network short circuit is at least equal to the I of the fuse that is used. Figure : definition of a fuse s operating zones. Information to provide on ordering The customer has to give certain key data when ordering to avoid any misunderstandings. This includes the following: b rated ; b operating ; b rated ; b transformer power (or motor power); b operating conditions (open air, cubicle, fuse chamber, etc.); b fuse length and cap diameter; b standards. For orders, please note the reference and characteristics of the fuses. Schneider Electric
Fusarc CF, Soléfuse, Tépéfuse, MGK Construction MT0009EN force (N) 0 70 0 50 0 30 0 0 0 5 5 0 3 travel (mm) Figure : this graph shows the value of the force provided by the striker according to its length of travel. End contact caps () Together with the enclosure, they form an assembly which must remain intact before, during and after breaking the. This is why they have to withstand mechanical stresses and sealing stresses due to overpressure caused by arcing. They also have to provide the stability of the internal components over time. Enclosure () This part of the fuse must withstand certain specific stresses (related to what has already been mentioned): b thermal stresses: the enclosure has to withstand the rapid temperature rise that occurs when the arc is extinguished. b electrical stresses: the enclosure has to withstand the restoring of after breaking. b mechanical stresses: the enclosure has to withstand the increase in pressure caused by expansion of the sand when breaking occurs. Core (3) This is a cylinder surrounded by ceramic fins onto which the fuse element is wound. The striker control wire together with the latter are lodged within the cylinder. They are insulated from the fuse elements. Fuse element () This is the main component of the fuse. Materials with low resistivity and which do not suffer wear over time are used. Our fuses have fuse elements with a carefully chosen configuration, defined after a lot of testing. This allows us to achieve the required results. Extinction powder (5) The extinction powder is made up of high purity quarzite sand (over 99.7%), which is free from any metal components and moisture. When it vitrifies, the sand aborbs the energy produced by the arc and forms an insulating component called fulgurite with the fuse element. Striker () This is a mechanical device which indicates the correct functioning of the fuse. It also provides the energy required to actuate a combined breaking device. The striker is controlled by a heavy duty wire which, once the fuse element has blown, also melts and releases the striker. It is important that the control wire does not cause the premature tripping of the striker, nor must it interfere with the breaking process. The strikers used on our fuses are of medium type and their force/travel characteristics (approximately joule according to standard IEC-.) are illustrated in figure. - contact caps - enclosure 3 - core - fuse element 5 - extinction powder - striker MT00 3 5 5 3 Cross sectional diagram of a fuse Schneider Electric 5
Fusarc CF Characteristics and dimensions MT00 Dimensions Ø5 33 striker * The following page gives the diameter and length of the fuse according to its rating. L* Ø* 33 Ø 3 Fusarc CF This is Schneider Electric s DIN standard fuse range. When designing this range, we paid particular attention to minimise power dissipation. It is increasingly common to use RMU units with SF gas as the insulating material. In view of these operating conditions, in which the fuse is inserted inside a hermetically sealed fuse chamber virtually without any ventilation, these fuses avoid the premature ageing, both of themselves and of the whole device, which would be caused by a non-optimised fuse. The enclosure in the Fusarc CF range up to A (rated ) is made from crystallised brown porcelain, which withstands ultra violet radiation and can therefore be installed both outdoors as well as indoors. Fuses with rated values greater than A have glass fibre enclosures and are only for indoor installations. You will find the full list of the Fusarc CF range in the table given on the following page. With rated s ranging from 3 to 3 kv and rated s of up to 50 A, customers can meet their exact requirements in terms of switchgear short circuit protection. Time/ fuse curves These characteristic curves show the rms value for each type of fuse and how this correlates with the associated fusing duration or pre-arc duration. Careful selection and design of fuse elements, together with meticulous industrial control, ensures an accuracy limit of ±%, i.e. more demanding than that recommended in IEC standards. During the design of our Fusarc CF fuses, we focused on a relatively high fusing at 0. s in order to withstand transformer making s and at the same time a low fusing at s in order to achieve quick breaking in the case of a fault. See page for the time/ characteristics of Fusarc CF fuses. Current limitation curves The Fusarc CF fuse range is specially adapted to protecting transformers from short circuits. Short circuits will not reach their maximum value if you choose a Fusarc CF fuse with a correct rated. For example, as shown in the limitation curves on page, for a short circuit whose presumed is 5 ka in an unprotected installation, the maximum value would be 7 ka for symmetrical flow and 3 ka for an asymmetrical case. If we had used a Fusarc CF fuse with a rated of A, the maximum value reached would have been.5 ka. Fusarc CF fuses installed in an SM type fuse-switch Fusarc CF fuses installed in an RM distribution cubicle 055N 055N Schneider Electric
Fusarc CF References and characteristics Reference Rated Operating Rated (A) Max. breaking I (ka) Min. breaking I3 (A) Room temp. resistance* (mω) Dissipate of power (W) Length Diameter (mm) (mm) (kg) 75737 AR 3. 3/3. 50 50.000 0. 5 9 3. 53 00 M0 0 7 0 5 500 M0.3 3 05 5 50 M0 3 50.5 5 50 M0.5 5 503 M0 0 55 53.5 3 5 50 M0 5 79 3. 35 5 505 M0 3.5 3 9 55.3 5 50 M0 7. 3/7. 0 35 5 507 M0 50.7 5 50 M0 3 5. 5 Weight 7. 5 509 M0 0 0. 5 5 M0 30 5.5 5 75735 BN 5 50 3. 75735 BP 50.000. 7 9 3. 75735 BQ 00.00. 95 75737 BR 50.00 0.9 95 5 53 007 M0 0 3 7 5 5 M0.3 3 39 5 5 M0 3 5 50.5. 5 53 M0 37 5 5 M0 0 55 5 55 M0 5 79 5 5 5 5 M0 3.5 3 0 59 9 55. 5 57 M0 / 0 35 7 5 5 M0 50 7. 70 5 59 M0 3 5 3. 5 50 M0 0 0 7 3. 5 5 M0 30 7573 CN 5 50 5,3 3 75735 CP 0.000 3.5 7 5 75735 CQ 00.00.7 7 5 5 M0 3 03 3 5 53 M0 3 7 50.5. 5 5 M0 5 79 7 7 9 55. 5 55 M0 3.5 5 7 5 5 M0 0 35 35 90 7 3. 53 00 M0 0 3 3 5 57 M0.3 0 3 0 5 5 M0 3 03 5 50.5.5 5 59 M0 7.5 /7.5 3 5 530 M0 0 55 3 5 5 53 M0 5 79 7 5 53 M0 3.5 5 7 37 55. 5 533 M0 0 35 35 9 5 53 M0 50 93 5 535 M0 3 3 5 9. 7 3.9 5 53 M0 0 330 3.5 5 5 537 M0 50 9. 53 009 M0 0 3 3 5 53 M0.3 3 5 5 5 539 M0 3 3 50.5.7 5 50 M0 0 5 5 5 5 M0 0 55 3 7 5 5 M0 5 79 5 79 5 53 M0 / 3.5 9 55. 5 5 M0 0 35 9 5 55 M0 50 3.5 3 5 5 M0 3 3 5. 7.5 5 57 M0 0 300 00 5 5 M0 50 3.5 0 5.7 53 0 M0 0 9 5 5 59 M0.3 3 750 39 5 550 M0 3 30 50 5 55 M0 5 9 50.5.9 5 55 M0 0 5 97 5 553 M0 3 0/3 5 0 79 33 33 537 55 3. 5 55 M0 3.5 3 7 5 555 M0 0 35 70 07 7 5. 5 55 M0 50 00 7 9 5 557 M0 3 50 35 0.5 *Resistances are given at ±% for a temperature of 0 C. Schneider Electric 7
Fusarc CF Fuse and limitation curves Fuse curve 3. - 7. - - 7.5 - - 3 kv Time (s) MT00 0 A.3 A A A 0 A 5 A 3.5 A 0 A 50 A 3 A 0 A A 5 A A 00 A 50 A 0. 0.0 0 00 Current (A) Limitation curve 3. - 7. - - 7.5 - - 3 kv Maximum value of the limited broken (ka peak) The diagram shows the maximum limited broken value as a function of the rms value which could have occured in the absence of a fuse. MT003 Ia =. Ik Is = Ik 50 A 00 A A 5 A A 0 A 3 A 50 A 0 A 3.5 A 5 A 0 A A A.3 A A 0. 0. Rms value of the presumed broken (ka) Schneider Electric
Soléfuse References and characteristics The Soléfuse ranges of fuses is manufactured according to standard UTE C00. Their rated varies from 7. to 3 kv. they can be supplied with or without a striker and their weight is of around kg. They are mainly intended to protect power transformers and distribution networks, and are solely intended for indoor installations (glass fibre enclosure). Electrical characteristics Reference Rated Operating Rated Min. breaking Max. breaking Room temp. resistance* Room temp. resistance* (A) I3 (A) I (ka) with striker (mω) without striker (mω) reference 7573 BC.3 3.5 50.5 7573 BE 0 50 5.7 7573 BH 7. 3./7. 3.5 57.5 50.5 7573 BK 3 35 50.3 7573 BN 5 5 50. 7573 CM / 500 50 7.7 7573 DL 7.5 3./5 0 00 0 5. 7573 EC.3 3.5 30 03. 7.3 75733 EC 7573 EE 0 30. 7. 75733 EE 7573 EH 3./ 3.5 57.5 30. 7.9 75733 EH 7573 EJ 3 5 30 3.5 39 75733 EJ 7573 EK 3 35 30.9 9.3 75733 EK 7573 FC.3 3.5 0 5 7573 FD 50 0 5.9 7573 FE 3 30/33 0 0 07. 7573 FF 0 0 33. 7573 FG 5 5 0 7573 FH 3.5 57.5 0 93 *Resistances are given at ±% for a temperature of 0 C. Dimensions striker MT00 50 Ø Ø55 35 50 3 max. Weight:.3 kg Schneider Electric 9
Soléfuse Fuse and limitation curves Fuse curve 7. - - 7.5 - - 3 kv Time (s) MT005 0.3 A A A 0 5 A 3.5 A 3 A 3 A 0 A A 5 A 0. 0.0 0 00 Limitation curve 7. - - 7.5 - - 3 kv Maximum value of limited broken (ka peak) Current (A) The diagram shows the maximum limited broken value as a function of the rms value which could have occured in the absence of a fuse. MT00 Ia =. Ik Is = Ik 5 A A 0 A 3 A 3 A 3.5 A 5 A 0 A A A.3 A 0. 0. Rms value of presumed broken (ka) Schneider Electric
Tépéfuse, Fusarc CF (metering transformer protection) References, characteristics and curves Type Reference Rated Operating We manufacture Tépéfuse and Fusarc CF type fuses intended for metering transformer protection which have the following references and characteristics: Characteristics Rated (A) Max. breaking I (ka) Min. breaking I3 (A) Length Diameter (mm) (mm) (kg) Tépéfuse 75 A < 75 B 3./ 0.3 0 0 30 7.5 0. Fusarc CF 53 00 MO 7. 3/7..5 3 9.5 9 50.5 0.9 *Resistances are given at ±% for a temperature of 0 C. Tépéfuse fuses are made only in glass fibre when intended for indoor usage. Fuses for transformer protection are made without strikers. Weight 53 000 MO / 53 003 MO.5 3 9.5 9 50.5. 53 00 MO / 53 00 MO.5 0 9.5 50.5. 53 005 MO 3 0/3.5 0 9.5 537 50.5. Dimensions 33 MT005 Ø 5 Ø 50.5 MT007 Ø7.5 33 L Fusarc CF 5 Tépéfuse 30 Fuse curve 7. - - - 3 kv Time (s) MT00 0 A 0.3 A.5 A 0. 0.0 Current (A) Schneider Electric
MGK References, characteristics and curves MGK fuses are intended to protect medium motors at 7. kv (indoor application). MT00 Dimensions Ø weight. kg 3 striker Electrical characteristics Reference Rated Operating rated (A) Min. breaking I3 (A) Max. breaking I (ka) Room temp. resistance* (mω) 7573 30 50. 75735 5 570 50. 7573 7. y 7. 900 50. 75737 00 50.53 7573 50 00 50 0.95 *Resistances are given at ±% for a temperature of 0 C. Fuse curve 7. kv Time (s) MT000 0 A 5 A A 00 A 50 A 0. 0.0 0 00 Limitation curve 7. kv Maximum value of limited broken (ka peak) Current (A) The diagram shows the maximum limited broken value as a function of the rms value which could have occured in the absence of a fuse. MT00 Ia =. Ik Is = Ik 50 A 00 A A 5 A A 0. 0. Rms value of presumed broken (ka) Schneider Electric
Selection and usage guide General Transformer protection MT00 I cc Short circuit General According to their specific characteristics, the various types of fuses (Fusarc CF, Soléfuse, Tépéfuse and MGK) provide real protection for a wide variety of medium and high equipment (transformers, motors, capacitors). It is of the utmost importance to always remember the following points: b Un of a fuse must be greater than or equal to the network. b I of a fuse must be greater than or equal to the network short circuit. b the characteristics of the equipment to be protected must always be taken into consideration. Even if only one fuse blows, it is recommended to change all three since the two others may have been subject to damage. Important: even if only one of the three fuses is in service, it is recommended to change them all because the two others may also have been subject to damage. I 3 I n Fuse () Transformer Closing () In this zone, any overloads must be eliminated by LV protection devices or by an MV switch equipped with an over relay. I n I Transformer protection A transformer imposes three main stresses on a fuse. This is why then fuses must be capable of: b withstanding the peak start up which accompanies transformer closing without spurious fusing. The fuse s fusing at 0. s must be higher than times the transformer s rated. If(0. s) > x In transfo. b breaking fault s across the terminals of the transformer secondary A fuse intended to protect a transformer has to break the circuit in order to prevent the transformer s rated short circuit level (Isc) from damaging the latter. Isc > If( s) b... withstanding the continuous operating together with possible overloads In order to achieve this, the fuse s rated must be more than. times the transformer s rated.. In transfo. < In fuse Choice of rating In order to correctly choose the fuse s rated s to protect a transformer, we have to know and take account of: b the transformer characteristics: v power (P in kva), v short circuit (Usc in %), v rated. b the fuse characteristics: v time/ characteristics (If 0.s and If s), v the minimum rated breaking (I3). b the installation and operating conditions: v open air, cubicle or fuse chamber, v presence or otherwise of permanent overload. Comment: whether used with Schneider Electric s SM or RM or in a device from another manufacturer, the equipment manufacturers own user s instructions must be referred to when choosing the fuse. Schneider Electric 3
Selection and usage guide Transformer protection Selection tables Fusarc CF fuses/din standard for transformer protection (rating in A) () () (3) Operating Rated Transformer power (kva) 5 50 75 5 00 50 35 00 500 30 00 0 50 0 000 5 3.5 0 50 3 3 0 3 7. 0 3.5 0 50 3 0 0 5 5 00 50 5 0 50 3 0 5 5 3.5 3.5 0 50 3 3 0 5 7. 0 3.5 0 0 50 3 0 0 5 5 00 50 5 0 50 50 3 0 5 0 5 3.5 0 0 50 3 3 0 7. 0 5 3.5 0 50 50 3 0 0 5 5 00 50 5 3.5 0 50 3 3 0 5 0 5 5 3.5 0 50 50 3 0. 7. 0 5 3.5 3.5 0 50 3 3 0 5 5 00 50 5 3.5 0 0 50 3 0 0 5 0 5 3.5 3.5 0 50 3 3.3 0 5 3.5 0 0 50 3 0 0 0 5 5 0 5 3.5 0 50 50 3 0 5 0 5 5 3.5 0 50 50 3.3 0 5 3.5 3.5 0 50 3 3 0 0 5 5 0 5 3.5 0 0 50 3 0 0 5 0 5 5 3.5 0 50 50 3 3. 7.5 0 0 5 3.5 3.5 0 50 3 3 0 0 5 5 3.5 0 0 50 3 0 0.3 0 5 5 3.5 0 50 50 3 3. 7.5 0 5 3.5 3.5 0 50 3 3 0 0 0 5 3.5 0 0 50 3 0 0 5 3.5 0 0 50 3 3 0 5 7.5.3 0 0 5 3.5 0 50 50 3 0 0 0 5 5 3.5 0 50 3 3 0 0 5 3.5 3.5 0 50 3 0.3 0 0 5 3.5 0 0 50 3 3 0 0 0 5 5 3.5 0 50 50 3 0 0 5 5 3.5 0 50 50 3.3.3 0 5 3.5 3.5 0 50 3 3 0 0 0 5 3.5 0 0 50 3 0 5 3.5 0 0 50 5 3.3 0 0 5 3.5 0 50 50 3 3 3 0 5 5 3.5 0 50 3 3 5 3.5 0 0 50 30 3.3.3 0 0 5 3.5 0 50 50 3 3 3 0 5 5 3.5 0 50 3 Soléfuse fuses/ute standard for transformer protection (rating in A) () () (3) Operating Rated Transformer power (kva) 5 50 5 00 50 35 00 500 30 00 0 50 0 3 7. 3.5 3 3 3 0 5 3.3 7. 3.5 3.5 3 3 0 0 5. 7..3 3.5 3.5 3.5 3 3 0 0 5 5.5 7..3 3.5 3.5 3.5 3 3 3 0 5 7..3 3.5 3.5 3.5 3 3 3 0 5. 7..3 3.5 3.5 3.5 3 3 0 0 5.3.3 3.5 3.5 3.5 3 3 3 0 0.3.3 3.5 3.5 3.5 3 3 3 0 3. 7.5/.3.3 3.5 3.5 3.5 3 3 3 0 5 7.5/.3.3 3.5 3.5 3.5 3 3 3 0 0 0.3.3.3.3 3.5 3.5 3 3 3 3.3.3.3.3 3.5 3.5 3.5 3 3 3 30 3.3.3.3 3.5 3.5 3.5 () Fuse ratings correspond to open air installation with a transformer overload of 30%, or to an indoor installation without transformer overload. () If the fuses are incorporated in a distribution switchboard, please refer to the selection table provided by the manufacturer of this device. (3) Although the ratings shown in bold type are the most appropriate, the others also protect transformers in a satisfactory manner. Schneider Electric
Selection and usage guide Motor protection Capacitor bank protection Fusarc CF fuse selection for motor protection Max. Start-up Start-up duration (s) operating 5 0 (A) No. of start-ups per hour 3.3 50 90 50 50 50 50 50 50 50 50 50 30 50 50 50 50 50 50 90 50 50 50 50 50 50 790 00 50 50 50 50 50 7 00 00 00 50 50 50 0 00 00 00 00 00 50. 00 00 00 00 00 00 50 00 00 00 0 00 00 00 0 00 3 0 5 50 5 5 5 0 5 5 5 5 5 30 5 5 5 5 5 5 5 5 5 5 5 5 70 0 33 0 0 0 0 0 0 0 0 0 0 0 0 0 0 9 3 0 0 0 0 0 3 3 3 3 0 0 3 3 3 3 3 3 0 73 50 3 3 3 3 3 7 50 50 50 3 3 3 50 50 50 50 50 3 57 50 50 50 50 50 50 Motor protection When combined with a contactor, the fuse provides a particularly effective protection system for an MV motor. The specific stresses that the fuses have to withstand are due to: b the motor to be protected; b the network on which it is placed. Stresses due to the motor b the start up (Id). b the start up duration (Td). b the number of successive start ups. b when the motor is energised, and throughout the start up period, the impedance of a motor is such that is consumes a Id which is significantly greater than the rated load In. Normally this Id is around times the rated (Id/In = ). b the start up duration Td depends on the type of load that is being driven by the motor. It is of around seconds. b we also have to take account of the possibility of several successive start ups in choosing the fuse rating. Stresses related to the network b the rated : the rated for MV motors is at most equal to kv. b the limited broken : networks with MV motors are generally high installed power networks with very high short circuit s. Choice of rating The fuse rating chosen depends on 3 parameters: b the start up ; b the duration; b the start up frequency. Capacitor bank protection Fuses intended to protect capacitor banks have to withstand special s: b when the bank is energised, the inrush is very high and can lead to premature ageing or fusing of the fuse element. b in service, the presence of harmonics can lead to excessive temperature rise. Choice of rating A common rule applied to any switchgear in the presence of capacitor banks is to derate the rated by 30 to 0% due to the harmonics which cause additional temperature rise. It is recommended to apply a co-efficient of between.7 and.9 to the capacitive in order to obtain the appropriate fuse rating, i.e..7 or.9 times the rated capacitor. As for transformers, it is necessary to know the rms inrush value and its duration. Schneider Electric 5
Selection and usage guide Motor protection Selection charts The 3 charts given below enable the fuse rating to be determined when we know the motor power (P in kw) and its rated (in kv). Chart : this gives the rated In (A) according to P (kw) and Un. Chart : this gives the start-up Id (A) according to In (A). Chart 3: indicates the appropriate rating according to Id (A) and the start-up duration time Td (s). Comments b chart is plotted for a power factor (cos ϕ) of 0.9 and an efficiency of 0.9. For values different to this, use the following equation: P In = ------------------------------ h 3Uacosϕ b chart 3 is given in the case of start-ups spread over an hour or successive start-ups. For n spread start-ups (n > ), multiply Td by n --. For p successive start-ups (p > ), multiply Td by p -- (see selection table). In the absence of any information, take Td = s. b if the motor start up is not direct, the rating obtained using the charts below may be less than the full load of the motor. In this case we have to choose a rating of 0% over the value of this to take account of the cubicle installation. MT003EN Example A 50 kw motor powered at. kv (point A, chart ) has a of 7 A (point B). The start-up, times greater than the rated = 0 A (point C, chart ). For a start-up time of s, chart 3 shows a rating of 50 A (point D). P (kw) 50 kw 0 A 00 Td (s) 3A 3A 0A 5A A C 00 50A 0 x00a 50A 00A D x50a Id (A) Td (s) In (A) kv kv.kv kv 5.5kV.kV A 3.3kV 3kV B 7 A x x x x x 0 A In (A) 0 P (kw) 0 00 0 Id (A) 00 Schneider Electric