type cfh series the cfh is a high quality range of aluminium housed power resistors offering environmental protection to ip55, 6kv dielectric strength, 1.8kw power dissipation, and the ability to absorb electrical pulses of up to 24kj. the use of advanced materials in the construction of this device enables operating temperatures of up to 450oc giving very high power density. key features 2200w in a 72cm 2 footprint ? unparalleled power density of 31w/cm 2 impressive pulse capability ? large active element can absorb up to 24kj no heatsink required ? dissipates up to 950w in free air slimline casing ? 30mm casing height for design flexibility environmental protection to ip55 ? reliable in the harshest conditions applications braking balancing capacitor charging & discharging crowbar filter power supplies electrical machinery inrush limiting characteristics - electrical cfh350 cfh500 cfh750 cfh1100 dissipation @ 25c with heatsink (watts): 650 850 1300 1800 without heatsink: 350 500 750 1100 with water cooled heatsink (40c): 750 1000 1500 2200 overload rating (5s): 4000 5600 8000 12000 ohmic value min (ohms): 0r5 0r5 0r5 0r5 max: 10k 18k 27k 27k tolerance: 5% standard maximum working voltage (dc/acrms) volts: 1500 2500 3500 4000 insulation resistance (volts): >=10000 m? dielectric strength (ac peak) volts: 4500 standard and 6000 special inductance (henries): 5-50 h at 7-70 h at 10-100 h at 20-200 h at 1000 hz 1000 hz 1000 hz 1000 hz standard heatsink area (mm 2 ): 1600 1600 1600 1600 thickness (mm): 135 135 135 135 protection grade (ip): ip55 mounting: vertically cable length: 300mm weight (g): 460 670 920 1250 heat dissipation: although the use of proprietary heat sinks with lower thermal resistance is acceptable, up rating is not recommended. the use of proprietary heat sink compound to improve thermal conductivity is essential. dimensions type cfh350 cfh500 cfh750 cfh1100 l 110 mm 160 mm 220 mm 320 mm p 60 mm 110 mm 140 mm 240 mm l p 30 l f ?6.2 71 95 82 2 literature no. 1773318 issued: 09-08 dimensions are shown for reference purposes only. dimensions are in millimetres unless otherwise specified. specifications subject to change. tycoelectronics.com passives.tycoelectronics.com aluminium housed power resistors type cfh series
literature no. 1773318 issued: 09-08 dimensions are shown for reference purposes only. dimensions are in millimetres unless otherwise specified. specifications subject to change. tycoelectronics.com passives.tycoelectronics.com aluminium housed power resistors type cfh series power rating. the dissipation power of a resistor depends also from the mounting position. if the resistor is mounted onto a surface, the latter takes part positively (if it is large and conductive) or negatively (if it is small and insulating) to the thermal dissipation. data of power rating are referred to a resistor mounted vertically, with terminals in the lower side and away from the nearest surface at least 10cm, in order to avoid thermal influence from the wall. surface temperature rise @ pn. during the load application, the surface temperature is not homogeneous, and it is higher on the flat surface of the resistor (surface that in the practical application shall be fixed to a heat sink or to a metallic surface to help the thermal dissipation). max.power rating of a resistor mounted onto a heat sink. standard heat sink is a common heat sink (as shown) used for the cooling of semiconductors, with two grooves for components mounting. the distance between the axes of these two grooves is 80 mm. in this case both heat sink and resistor will be mounted upright. the length of the heat sink shall be at least 40 mm longer than the resistors body (20 mm for each side). power rating of a resistor mounted on a water-cooled heat sink. if the heat sink is water-cooled, power dissipation increases considerably, and the limiting power rating is due to temperature of the resistor body. in the case illustrated in the specifications board, the temperature of the heat sink is 40c and the resistors surface reaches 300c. in this case too, the length of the heat sink shall be at least 20 mm longer than the resistors body. absorbed energy @ 250c t. it represents the quantity of energy stored into the resistor when it has reached 250c of temperature rise. the above indication is an index of the thermal capacity of the resistor. absorbed energy in 5. it gives an index of behaviour of the resistor to short overloads. absorbed energy in time 0.2. during a short impulse (from 0 to 2 sec.), the resistor may stand only the energy that the thermal capacity of the resistance wire is able to absorb. in fact the phenomenon is too short to let significant heat conduction from wire to filling material. the energy absorbed from the resistor in this case results from this simple equation: q j = cs p t where: - qj is the quantity of energy expressed in joule, - cs is the specific heat of the employed resistance alloy expressed in j g -1 ? k -1 , - p is the weight of the wire in grams and - t is the rise of temperature, expressed in k, reached by the wire during the impulse. as type and quantity of wire are characteristics of every resistance value and resistor model, the acceptable temperature limit of wire is relevant. this limit (@ 25c) is: - 500c for the standard operations (steady state load); - 800c for not repeatable overload. the following graphs show these two conditions for each resistance value and resistor type. application notes 10 cm 135 80 pulse energy absorbed energy for wire temperature of 500c (impulse time 0,2) absorbed energy for wire temperature of 800c (impulse time 0,2) 0.2 1 10 100 1000 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 energy (kj) resistance (ohms) cfh1100 cfh750 cfh500 cfh350 0.2 1 10 100 1000 24 22.5 21 19.5 18 16.5 15 13.5 12 10.5 9 7.5 6 4 2 energy (kj) resistance (ohms) cfh1100 cfh750 cfh500 cfh350 these graphs are irregular owing to the necessity to adapt the commercial dimension of wire to the resistance range, however they are enough to show the trend of this characteristic. should the energy value of an impulse be too close to the limits given from these graphs, it is suitable to consult the factory for further information concerning the precise value of absorbed energy for the used resistor.
literature no. 1773318 issued: 09-08 dimensions are shown for reference purposes only. dimensions are in millimetres unless otherwise specified. specifications subject to change. tycoelectronics.com passives.tycoelectronics.com aluminium housed power resistors type cfh series resistance range. the resistance range fulfils almost all the use of power resistors, but in cases of special requirements, lower or higher resistance values are available on request as well as closer tolerances. inductance. the inductance changes with the resistance value and is not very influenced from frequency. on request the cfh resistors are available with non inductive windings (airton-perrys system) and are identified by adding the letter n after the cfh identification (e.g.cfhn500). the inductance of the cfhn resistors is less then 1 h. parasitic capacity. parasitic capacity does not depend on the resistance value, but it changes with frequency. the supplied value are just referred to 1 khz (the higher) and 100 khz. during normal load conditions the effects of parasitic capacity are negligible. however in the presence of transients of high voltage <10sec, the housing may be a source of interference for most sensitive electronic circuits. for a correct grounding of the housing, cfh resistors are available, on request, with a threaded hole m5. limiting element voltage. this is the maximum voltage, which should not be exceeded during the application conditions. the rated values are rather elevated, but special designs with higher limiting element voltage are available for particular requirements. the limiting element voltage of non inductive resistors is lower than the standard resistors (please contact us for advice). insulation resistance and dielectric strength. after a long load time, the insulation resistance of cfh resistors keeps elevated as the employed insulating material does not get damaged despite the high thermal conditions. thermal time constant. the dimension of the resistor models is proportional to power rating and weight, therefore their behaviour during the rise of temperature, when the rated power is applied, is analogous. of course the application of a heat sinks or the mounting of the resistor on a surface, will modify the thermal time constant which is peculiar for each application. application notes (continued) thermal time constant kt 5 1015202530354045 390 350 300 250 200 150 100 temperature (c) time (mins) 2 / 3 rated power 1 / 2 rated power rated power kt
derating curve surface temperature rise 0 100 200 300 400 500 2500 2000 1500 1000 500 0 power (w) heatsink temp. (degc) cfh1100 cfh750 cfh500 cfh350 0 200 400 600 800 1000 1200 1400 1600 1800 2000 400 350 300 250 200 temperature rise (c) power (w) cfh750 cfh1100 cfh500 cfh350 literature no. 1773318 issued: 09-08 dimensions are shown for reference purposes only. dimensions are in millimetres unless otherwise specified. specifications subject to change. tycoelectronics.com passives.tycoelectronics.com aluminium housed power resistors type cfh series how to order cfh 750 a 680r j common part 350 w 500 w 750 w 1100 w power rating a - 300mm flying leads b - 1000mm flying leads termination resistance value cfh - aluminium housed power resistor 0.1ohm (100m?) r10 1 ohm (1000m?) 1r0 1k (1000?) 1k0 tolerance j C 5%
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