Dynamic Braking (Db) Hardware; Appendix A - Baldor 18H Series Installation & Operating Manual

Appendix A

Dynamic Braking (DB) Hardware

MN718
Whenever a motor is abruptly stopped or forced to slow down quicker than if
allowed to coast to a stop, the motor becomes a generator. This energy appears on the
DC Bus of the control and must be dissipated using dynamic braking hardware. Dynamic
braking (DB) hardware can be a resistor or transistor load. Table A-1 provides a matrix of
DB turn ON and turn OFF voltages.
Table A-1
Parameter Description
Nominal Voltage
AC Input Voltage Range
Overvoltage Fault (Voltage exceeded)
DB ON Voltage
DB UTP *
DB OFF Voltage
DBUTP (DB Upper Tolerance Peak) + 1.02 x 2 x V
*
Braking torque and time should not exceed the available drive braking torque and time
rating. The drive braking torque is limited to the available peak current and peak current
time rating of the control. If the peak current or peak current time limit is exceeded during
braking, the control may trip on an over voltage or a regen power fault. Selecting an
oversized control or a line regenerative control should be considered in these cases.
Selection Procedure
1. Calculate the Watts to be dissipated using the following formulas for the
appropriate load type.
2. Identify the control model number and determine which braking hardware is
required based on the model number suffix: E, EO, ER, MO or MR.
3. Select appropriate braking hardware from Baldor 501 Catalog or Tables A-2,
A-3 and A-4.
Hoisting Load Calculations
1. Calculate braking duty cycle:
Duty Cycle +
2. Calculate braking Watts to be dissipated in dynamic braking resistors:
duty cycle
Watts +
where: lbs = weight of load
FPM = Feet Per Minute
efficiency = mechanical efficiency
i.e., 95% = 0.95
Continued on next page
230VAC
180-264VAC
400VDC
381VDC
388VDC
375VDC
Lowering Time
Total Cycle Time
lbs FPM efficiency
44
Control Input Voltage
460VAC 575VAC
340-528VAC 495-660VAC
800VDC 992VDC
762VDC 952VDC
776VDC 970VDC
750VDC 940VDC
L*L
Appendix A-1