Altivar® 58 TRX AC Drives
Dynamic Braking Resistor Kits
DB resistor requirements:
Peak braking power required to develop braking torque (Tb) when decelerating from a given speed
Pi = Tb x Nbase/(7.04) = (1.97 x 1740)/(7.04) = 487 W
The braking power that must be absorbed for a time (td) during stopping or speed changing operation: Pd = 0.5 x Pi = 0.5 x 487 = 243 W for a period of td seconds
The average braking power that must be dissipated during a machine cycle:
Pa = Pd x td/tc = 243 x 5/30 = 40.5 W
Capability of VW3A66711 DB resistor assembly for ATV58U72N4 controller:
Peak braking power that can be developed with VW3A66711 DB resistor assembly with controller
configured for 460 Vac input line operation: P | = (V )2/R | db | = (850 V)2/120 Ω = 6020 W |
i | db |
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The braking power that can be absorbed for td (based on DB resistor hot state
characteristic curve shown on page 37): |
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P | d | = R | x ((Multiple of I | r | at t ) x Ir)2 | = 120Ω x (3.5 x 1.0)2 | = 1470 W |
| db |
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Since Rdb limits the peak current that can be drawn from the drive controller DC bus, the value of [(Multiple of Ir) x Ir] must be limited to no greater than (√ pi/Rdb).
The average braking power that can be dissipated continuously:
P | = R | x (I )2 | = 120 Ω x (1)2 = 120 W |
a | db | r |
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For this example, the VW3A66711 DB resistor assembly will work as intended for the application.
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| 09/2003 |
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