Electrically-operated crane control unit 4011

Type 4011 AC Crane Hoist Controller, Dynamic Lowering This AC Dynamic Lowering hoist motioncontroller provides braking action by applying asingle-phase connection to the primary of athree-phase wound rotor motor. It isrecommended where slow lowering speeds arenot required for overhauling loads of 50% ormore.Fire speed points are provided for hoisting. Thefirst-point hoist applies weak torque for hookingon, slack cable take-up and light loads.Successive hoist points continue to cut outsecondary resistors and increase motor torque.Lowering is controlled by three master switchpoints. In the first-point lowering, sing-phasepower is applied to the motor primary with adynamic braking connection. An overhaulingload will lower at a speed depending on theload, but a non-overhauling load will not lower.On second-point lowering, weak down torquedrives down non-overhauling loads and permitsaccurate inching of light loads If the motor accelerates to 80% speed, the lastaccelerator closes and drives the load down inregeneration. This prevents motoroverspeeding with an overhauling load on thehook. The third-point lowering accelerates themotor to full speed similar to full-speed hoisting.Type 4011 ac dynamic lowering control panelsare suitable for use with ac wound rotor motorson crane hoist drives.Type 4011 controllers are for use on hoist orother overhauling drives that do not usemechanical or electric load brakes, and whereaccurate positioning and slow steady speedsare not required.Panels are arranged for use with a power limitswitch and separate ac or rectifier operated dcbrakes.