New from Softstart UK is the Solbrake range of dc injection brakes, providing dynamic braking of ac squirrel cage motors from 220-690V. Manufactured by Solcon Industries, these solid state motor brakes dramatically reduce motor stopping time compared with either regenerative braking or reversing, so increasing safety with hazardous machinery or enabling production rates in machine tools and high inertia loads to be increased.
The dynamic brakes provide fast, smooth, frictionless braking of squirrel cage motors by injecting controlled dc current into the motor windings. This induces a stationary magnetic field which exerts a braking torque on the rotor. The smooth, soft stopping helps to prevent wear and tear of mechanical parts, whilst the adjustable braking torque allows the required stopping time to be precisely set against the load size.
Maintenance free and highly reliable, the Solbrake provides an inherently more predictable braking characteristic than simply reversing the drive, which can result in the motor rotation actually going into reverse with severe operational and safety implications. Further, unlike regenerative braking which requires the installation of heavy duty resistors to absorb the energy, the Solbrake offers inherently simple installation in electrical switchgear.
As well as improving on traditional electrical braking technologies, Solbrake dc injection brakes complement mechanical braking systems, bringing motor speed softly to zero before the mechanical brake is operated. Using the mechanical brake only for holding instead of actually stopping the motor significantly reduces wear.