Rockwell Automation AK DBU - Dynamic Braking Unit 600/690 VAC - Manual (Page 30)

A-4 Specifications
The DBU contains the BUB diagnostic card which includes the two red
indication LEDs Power ON and Brake ON.
Table A.1 Function/State of Indication LEDs
The time constant (t) of the brake resistor: t = L/R, must be <40 µs
L: Effective inductance of the brake resistor and cable
R: Resistance of the resistor (R)
Due to the many different types of brake resistor constructions their
inductance varies widely. Specifically wire wound resistors on ceramic
core can have high inductance. For example a brake resistor with 3.1
ohm resistance shall not have more than 110µH inductance if the cable
inductance for 30m (90ft) is assumed to be 10µH..
Table A.2 provides the recommended fuse ratings for the DBU.
The recommended fuses meet the UL and IEC requirements and are
based on 40°C (104°F) and the U.S. National Electrical Code. Other
country, state or local codes may require different ratings.
If the available fuse ampere ratings do not match those recommended,
the next higher fuse rating should be chosen.
• IEC – BS88 (British Standard) Parts 1 & 2,
EN60269-1, Parts 1 & 2, type aR or equivalent should be used.
• UL – Recognised; A100P (Ferraz) or FWJ (Bussmann) must be used.
Table A.2 Recommended Short Circuit Protection Fusing
Notes:
(1) Minimum protection device size is the lowest rated device that supplies maximum
protection without nuisance tripping.
Diagnostic Card BUB
Function LED Status Condition
DC Power ON ON when DC bus voltage exceeds 50V
Brake ON ON when braking current flows
Brake Resistor Specifications
Fuse Ratings
AC Line DBU Rating Fuse Fuse Holder
Volt kW Amps Amps Volt Type Type Manufacturer
600 268 300 300 700-800 FWJ-300 BH-3 Bussmann
A100P300-4TI P266L Ferraz
690 305 300 315 1000 G300547 SI DIN 110 630 Ferraz