Any fault condition must be eliminated and the latched fault indication must be cleared before power can be switched on to the unit under test. The BPU intentionally does not have a remote control or external control interface. Not having a remote/external control eliminates the chance that an erroneous or rogue command can inadvertently apply power to the unit under test or change voltage thresholds. The BPU uses comparator circuits to detect the fault conditions. The comparator outputs feed a FPGA that implements logic functions and provides digital filtering. Recessed trim pots set the comparator threshold levels from the front panel. The Over/Under/Reverse thresholds can be displayed while adjustments are made. The BPU also incorporates a separate crowbar circuit for additional over voltage protection. For battery simulator applications, the 150A series diode can be jumpered across allowing current to flow either direction.

The BPU is available with several options. One option includes a switched AC outlet. The switched outlet can be used to power a large 'Spacecraft is Powered' warning lamp or be used to power an elapsed counter. The elapsed counter can be useful to keep track of burn-in time. Other options include changing the circuit breaker size, changing the circuit breaker to a fuse, a 120VDC version, additional auxiliary outputs, etc.


BPU Model

• Standard BPU - (50 Volt / 30 Amp) 3-aux outputs
• Standard with 4-aux outputs
• Standard w/different circuit breaker (customer tbd)
• Standard w/fuse instead of CB (customer tbd)
• Standard with switched AC outlet
• 120 Volt BPU - (120 Volt DC / up to 30 Amp fuse)
• ELSE BPU - (Remote controlled launch support)
  

The Bus Protection Unit (BPU) is a ground support element designed to protect a spacecraft or flight box against wrong voltage levels during integration and test. The BPU can detect an Over/Under/Reverse-Voltage Fault Condition. A BPU will not switch on if a Fault Condition is present and will switch off if a Fault Condition occurs after power is switched to the unit under test. The BPU primarily protects against voltage faults but does include current protection by way of a DC circuit breaker. The BPU must manually be switched on from the front panel.