the motor and th i s brak ing energy i s re s i stors on stee l , offers h igh pu l se 1 .5kW , 2kW , 3 .5kW , 5kW , 7kW IRC th i ck f i lm p lanar power re s i stors In an AC ma ch ine dr ive , the l ine fed AC an e levator, where the smooth de ce lerat ion to a comp lete stop i s a ch ieved by brak ing IRCUnder braking conditions, power will ow back into the DC rail and as the reverse DC current cannot return to the AC supply because of the recti er stage, the energy ow into the link capacitor causes the DC link voltage to rise. When the DC link voltage reaches the maximum permitted limit, the electronic braking circuit switches on and o in a pulse mode. The pulse is usually 1 milli-second time interval during its normal on period for up to two seconds and with a duty cycle of perhaps 1:5 to 1:10. However, there appears to be no unifying standard in industry as to what this duty cycle should be. In an overload or fault condition, the braking resistor is designed to go open circuit in a fail-safe manner with no short circuit to ground and be ame retardant. A low inductance on the resistor is generally preferred to allow e ective electronic switching. IRCs Dynamic Braking Resistor is an insulated stainless steel substrate on to which a thick lm circuit / resistor is printed. A high temperature overglaze protects the surface of the resistor. The dielectric layer provides a high voltage insulation breakdown typically in the region of a min. 2.5 kVDC. The WDBR gives a fast thermal response (high power dissipation as heat is rapidly transferred to the heat sink) because of the low thermal mass and an improved temperature distribution from e ective element designs. In addition, the substrate itself also behaves as a heat sink and provides mechanical strength and robustness. These coupled with excellent closely matched thermal expansion coe cients between the stainless steel and the dielectric lm enable the resistor to withstand severe temperature cycling (up to 400C) in high power pulse applications. The intrinsic robustness, thermal capacity, e ective resistive track designs and electrical performance of the thick lm on steel braking resistor o er a high performance, cost competitive solution to dynamic braking. Extensive power pulse laboratory testing has demonstrated good stability and reliability in the WDBR resistor. WDBR1 WDBR5 WDBR2 WDBR3 WDBR7 Standard Resistance Values (ohms) ** 12, 22, 47, 100, 150 47, 100, 150 47,100, 150 Resistance tolerance Max pulse power (>50,000 cycles per Fig 2) (Ref 1) 1.5kW 2kW 3.5kW 5kW 7kW Stability (nominal load) after 50,000 cycles) Maximum resistor hot spot temperature 365C Minimum dielectric withstanding voltage (DWV) 2500 VDC 180W 200W Maximum continuous load without cooling (ref 2) * 260W 270W 280W Maximum continuous load with cooling (ref 2) * 700W 780W 900W 1100W 1490W Derating SeeFig 1 Inductance (Typical) <3 H <3 H <3 H <4 H <6 H Ref 1 Testing carried out on a heatsink (thermal resistance 0.53C/W), force cooled at 5 m/s air velocity for 50 kcycles. Ref 2 Testing carried out on a heatsink (thermal resistance 0.53C/W), with no air-cooling, RT = 25C. * Limited by the solder type, the Maximum continuous load can be improved with HMP solder. ** Resistance values available from 1 to 100 k. Contact IRC for custom values - afdsales irctt.com