DC Crane Control Components
UNICO’s 2000 series features a full line of products engineered specifically for constant-potential DC crane retrofits. Depending upon the application, these modular components can be selected to provide superior motor control, integral braking control, and auxiliary power solutions using existing motors and plant distribution systems.
The anti-regen diode (ARD) is a high-power blocking diode that isolates the plant DC power supply from the drive system. It is commonly used with systems powered by traditional diode-bridge DC bus supply rectifiers or diesel-driven DC generators. The unit prevents overhauling or regenerating loads from “pumping up” the plant bus by blocking current flow back to the rails or festoons.
The DC converter (DCC) filters the incoming line to stabilize the bus voltage and protect against abnormal overvoltage and undervoltage conditions. The unit is commonly used with systems powered by traditional diode-bridge DC bus supply rectifiers or diesel-driven DC generators.
The amplifier converts the filtered DC bus into variable field and armature voltages for controlling a shunt- or series-wound DC motor. It uses insulated gate bipolar transistors (IGBTs) and pulse-width modulation (PWM) techniques controlled by a digital signal processor (DSP) and patented digital current regulator (DCR) technology. Crane-specific software provides extensive control features for optimizing the performance, safety, and productivity of cranes.
An optional dynamic brake (DB) eliminates excess regenerated energy by shunting it to resistors to be dissipated as heat. Regenerated energy is created during lowering, stopping, and plugging operations. A single dynamic braking unit and resistor grid serves all drives in the system.
The brake driver precisely coordinates an electrically actuated brake with the motor shaft to provide smoother control and extend brake life. Field-forcing techniques allow snap activation of either disc- or drum-type brakes.
AC Power Supply
An optional stand-alone power supply provides auxiliary AC power from the DC bus. The unit converts 230 V DC into single-phase 230 V AC at 60 Hz for powering lighting, air conditioners, fans, heat exchangers, and other devices. A step-down transformer can be added to allow ordinary 115 V tools, test equipment, and other conveniences to be used on the crane.