What is DB ?
"DB" stands for dynamic braking. Applications with high inertia, regenerative loads, cyclic loads, or any application with "regen energy" may require dynamic braking. Dynamic braking uses a transistor and a resistor to absorb this energy and prevent the VFD from tripping on overvoltage (OVT).
When is a DB unit is required?
The DB unit (DBU) is used to describe the transistor or switching circuit that directs energy to a dynamic braking resistors (DBR). Most LS VFDs up to 30HP have a built-in DBU. Larger capacity VFDs require an external DBU.
Not all kinds of loads require DB circuit. DB is not needed at the loads such as fan and pump which have no restriction of acceleration and deceleration time or when the load has a small inertia.