The Bus Protection Unit First Generation (BPU 1G) is a ground support element designed to protect spacecraft or flight box against wrong voltage levels during integration and test. The BPU 1G can detect an Over/Under/Reverse-Voltage Fault Condition. A BPU 1G 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 1G primarily protects against voltage faults but does include current protection by way of a DC circuit breaker. The BPU 1G must manually be switched on from the front panel.

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 1G 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 1G uses comparator circuits to detect fault conditions. The comparator outputs feed a FPGA that implements the 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 1G also incorporates a separate crowbar circuit for additions over voltage protection. For batter simulator applications, the 150A series diode can be jumpered allowing current to flow either direction.

The BPU 1G 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 a 120 Volt Version, changing the circuit breaker size, changing the circuit breaker to a fuse, additional auxiliary outputs, etc.

• 0 to +50 Volts DC
• 0 to +/-50 Amp
• Digital Input / Output Voltage Meters
• Digital Current Meter
• Fault Indication LEDs
• Front panel adjustable thresholds for Over/Under/Reverse fault detection
• Analog and Digital filtering on threshold signals
• Under Voltage Detect Disable Switch
• Separate Over Voltage Crowbar
• Shunt Diode on output
• 150A Series Diode with bypass jumper
• Series Diode Bypass Indicator
• Three auxiliary power outputs with fuses
• Rear panel accessible voltage & current test points
• Heavy duty mercury relay used to switch power. Mercury contact eliminates 
  contact wear and contact bounce
• 19-inch rackmount chassis, 7-inch Rack Height