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 = 6020 W

i

db

 

The braking power that can be absorbed for td (based on DB resistor hot state current-time

characteristic curve shown on page 37):

 

P

d

= R

x ((Multiple of I

r

at t ) x Ir)2

= 120x (3.5 x 1.0)2

= 1470 W

 

db

 

d

 

 

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 x (1)2 = 120 W

a

db

r

 

For this example, the VW3A66711 DB resistor assembly will work as intended for the application.

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© 2000–2003 Schneider Electric All Rights Reserved

 

09/2003

 

 

 

 

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Image 36
Schneider Electric manual Altivar 58 TRX AC Drives