Overhead Crane Retrofitting – Case study

PROJECT SUMMARY
  • Project: 175T/25T Heavy Lift Crane NASA Vehicle Assembly Building (VAB)
  • Location: Cape Canaveral, FL, USA
  • Application: Heavy Lift Crane NASA Vehicle Assembly Building (VAB)
NIDEC'S ROLE

NASA’s SLS program requires the use of heavy lift cranes with very precise operation. Retrofitting the existing obsolete control system was a requirement for the support of this program. The existing crane was mechanically sound and originally designed to CMAA requirements.

Scope of Supply
Crane for NASA
THE CHALLENGE
THE SOLUTION

Due to the critical nature of the cargo and precision needed during assembly; no single point of failure can stop the crane from operating.

Design specification called out stand-alone AC drives with capacitor base power factor correction equipment [2]. NIS Americas’ engineering and sales team provided an alternate proposal utilizing common-bus AC drive technology. Multiple active front ends (AFE’s) were supplied so that a failure of one unit would not stop the crane from working at full capacity. In addition, the AFE units provide unity power factor back to the main power system [2]. Based converters also provided power back to the grid which could be reused in place of losing it through heat in resistor banks.

Each section of the crane had multiple motors for operation. Hoist sections had two motors which were designed to allow the crane to operate on one if needed. Travel motions were also designed with multiple motors in case of failure. NIS provided redundant AC inverter
drives that could operate as either a hoist or travel section. This reduced the number of drives required for back-up mode of the cranes.

All electrical equipment required for the project had to meet UL requirements. Panels were manufactured to UL 508 [3] which also included a site inspection of the equipment in order to certify the system installation. Control equipment also had to meet UL519 at the main
power feed of the crane. NIS AFE’s provided the PF correction and harmonic filtering that met the UL519 specification.