LEESON SCR Thyristor Motor Control - Manual (Page 40)

34 Operation SPEEDMASTER™ OPERATION MANUAL
Sizing the dynamic brake resistor
Size the dynamic brake resistor according to the motor current
rating (Table 3). The dynamic brake resistance listed in the table
is the smallest recommended resistance allowed to prevent
possible demagnetization of the motor. The motor stops less
rapidly with higher brake resistor values.
Table 3. Recommended Dynamic Brake Resistor
Sizes
Minimum Minimum
Motor Armature Dynamic Brake Dynamic Brake
Current Rating Resistor Value Resistor
Wattage
Less than 2 ADC
1 ohm 1W
2–3 ADC 5 ohm 5W
3–5 ADC 10 ohm 10W
5–10 ADC 20 ohm 20W
10–17 ADC 40 ohm 50W
For motors rated 1/17 horsepower and lower, a brake resistor is
not necessary since the armature resistance is high enough to
stop the motor without demagnetization. Replace the dynamic
brake with 12 gauge wire.
NOTE: Models 174105, 174308 and M1740006 are factory-
equipped with dynamic braking.