The resistor is marked on the housing with indelible ink high temperature
FAIRFILD – RFZ/C 300 150R 5% WW/YY (week / year)
Warning: Units must never be mounted with the terminals uppermost
The resistor is packed in a way to preserve incidental damages due to transport. To avoid resistor’s break we recommend to never take it from the cables and to handle with care inside the original boxes provided by the factory.
Every effort has been made to ensure that the information in this datasheet is accurate. Fairfild is not responsible for printing or clerical errors. All properties and characteristics mentioned in this datasheet are only for informational purposes. The information in this datasheet is offered solely for your consideration and should not be taken as a warranty or representation for which we assume legal responsibility. The customer bears all responsibility for use and application of Fairfild products. There is no responsibility of the manufacturer for any damage to persons and properties in case of improper use. Fairfild reserves the right to change specifications without prior notice.
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XXX Model 100, 160, 200, 260, 300, 320 RRRR Resistance value (nominal at 20°C)
RFZ/C 300 150R 5%
RFZ/C is the name of the product
300 is the model
150R means 150 Ω that is the nominal ohmic value at 20°C
5% is the tolerance on the ohmic value, in this case the value of the resistor is accepted when is within 142.5 Ω ÷ 157.5 Ω
Active materials: calculation for min ohmic value are made considering wire material CuNi44, whereas max ohmic value refers to wire material FeCrAl. Resistors can be made also with NiCr alloys. Temp. Coefficient Resistance depends on the used alloy, typically it is between 20 and 240 10-6/°C.
The standard version cable is single core with flexible conductor silicone rubber insulated with fiberglass braid.
For cross section AWG14 and AWG16 the cable is classified 200°C – 600 V and made according to UL Style 3071.
For cross section 1 mm2, 4 mm2 and 6 mm2 the cable is classified 180°C – 500 V and made according to IEC EN 60228 cl. 5 /CEI EN 50363-5.
The tolerance on cable length is ±5 mm. The choice of cross section to be used depends on the current that flows in the resistor.
Internal thermal switch 160±5°C (rated voltage: 250 V; rated current: 2,5 A; leads single core conductor silicone rubber insulated cross section 0,25 mm2 length 300 mm), it is an option and must be specified in the order.
Housing is aluminum extrude, it is oxidized to prevent corrosion.
Standard tolerance on ohmic value is ±5%.
Max power can be supplied to the resistor for not more than 60 minutes.
Picture above refers to RFZ/C 100.
MECHANICAL DATA & DRAWING
Unless otherwise specified, applicable standard of general tolerances for linear and angular dimensions is ISO 2768-1 class c; applicable standard for aluminum profile is EN 755-9:2008.
CYCLIC WORK LOAD
Case resistors are mostly used for overload operation, such as precharge of capacitors, dynamic braking of VFD, crowbar operations.
We can distinguish between 3 typical overload conditions: one is the isolated single pulse (emergency braking, precharge in case of short circuit or abnormal duty), the second one is the cyclic work load (i.e. braking of a lift), and the third one is a long overload (i.e. due to a fault in the system).
In all 3 cases, we can state that for pulses of duration less than 60 s, the mass of the wire must be taken in account to define the admissible overload. The mass of the wire depends on the ohmic value.
Unless the pulse is very short (<0,5 s), the mass of the quartzite sand inside plays an important role for the calculation of the global thermal capacity. The longer is the duration of pulse, the higher is the multiplier of the thermal capacity of the wire.
Fairfild technical office is at your disposal for further detailed information.
As far the operation in the cyclic work load condition, we can easily calculate the admissible braking power in respect off the duty cycle (ton / total time): Braking power = Rated power * (1 / Duty cycle)
This is valid only if the period does not exceed 240 s.
In the following table is shown the max power that is possible to supply for different duty cycle and period.
MECHANICAL DATA & DRAWING
In the following graph is shown, for ohmic value range between 10 Ω and 150 Ω, the maximum pulse energy of max 1 second that is possible to supply to the resistor in a cyclic load. In case of isolated pulse, the value can be multiplied times 2.
The rater power stated in this datasheet refers to the resistor mounted in horizontal position (with no possibility to exchange heat in the bottom direction) at the ambient temperature of 25°C and 250°C on the external surface. The power dissipation is influenced by:
Mounting position and arrangement (wall, heat – sink)
Number of resistors mounted together (grouping)
Ambient temperature (in free air or inside an enclosure)
Ask the appropriate test reports for more details. See the following graph to know the external temperature corresponding to a certain