The SPS-100-88-21091 frequency relay (NSN 5930-01-396-2940) serves as an essential protective device integrated into diesel-powered electric generators, including tactical field units such as the SPS-100-88-21091 Tactical Quiet Generator (TQG). Engineered to military-grade specifications, this frequency relay continuously monitors generator output and initiates an automatic shutdown under abnormal operating conditions, specifically targeting overspeed scenarios indicated by frequency deviations.
Functional Overview
The frequency relay operates by sensing deviations in the output frequency of the generator’s alternator. In nominal operation, generators such as the SPS-100-88-21091 are designed to produce 60 Hz AC output under full load conditions. Frequency instability, particularly excursions above acceptable upper thresholds (typically above 63 Hz in many military designs), signals a mechanical overspeed condition.
Upon detection of such deviations, the frequency relay:
- Triggers a trip command to the generator’s control system
- Interrupts engine operation, either through direct shutdown or by initiating a fault lockout sequence
- Prevents mechanical damage to the alternator, connected load equipment, and ancillary systems
This protective action is critical for safeguarding sensitive battlefield electronics, preserving generator longevity, and maintaining operational continuity under dynamic field conditions.
Technical Characteristics
Key characteristics of the SPS-100-88-21091 frequency relay include:
- Continuous real-time monitoring of AC output frequency
- Preset trip points, calibrated in accordance with MIL-DTL-53133/3 requirements for Tactical Quiet Generators
- High-speed response time, allowing near-instantaneous actuation upon threshold breach
- Solid-state architecture, providing enhanced reliability under shock, vibration, temperature extremes, and EMI exposure
- Field-replaceable module design, facilitating rapid maintenance and minimizing generator downtime
Integration Parameters
- Mounting: Internal to generator control panels
- Operating Temperature Range: -40°C to +70°C
- EMI Compliance: MIL-STD-461 for electromagnetic compatibility
- Environmental Standards: MIL-STD-810 for vibration, shock, humidity, and dust resistance
- Reset Modes: Configurable for manual or automatic reset following a trip event
The device architecture prioritizes durability and fault tolerance, aligning with overall system design objectives for deployable military power systems.
Application in the SPS-100-88-21091 Generator System
Within the SPS-100-88-21091 generator platform, the frequency relay functions as a core element of the broader generator protection strategy, alongside:
- Low oil pressure cutoff
- High coolant temperature cutoff
- Overvoltage protection
- Short-circuit protection
The relay directly enhances mean time between failures (MTBF) performance metrics and contributes to the generator’s high operational availability rate, which is critical for military readiness.
In field environments, the relay’s ability to rapidly disengage power during unstable operating conditions:
- Prevents catastrophic mechanical failures such as rotor throw or winding insulation breakdown
- Protects attached load circuits, including radar, communications, life-support, and computing systems
- Reduces field repair and replacement burdens, enhancing logistical sustainability
Maintenance and Diagnostics
The SPS-100-88-21091 frequency relay is designed for minimal maintenance. Standard service procedures involve:
- Periodic functional verification during preventive maintenance inspections (PMI)
- Calibration checks as specified in the generator’s technical manual
- Module swap capability, enabling fast in-field replacement without requiring specialized tools
- System diagnostics may report frequency trip events via fault codes or indicator lights on the generator control panel, assisting field technicians in troubleshooting.
Safeguarding Tactical Power Systems
The SPS-100-88-21091 frequency relay (NSN 5930-01-396-2940) is a mission-critical subsystem that provides generator overspeed protection by actively monitoring and controlling output frequency parameters. Its high-reliability design, environmental hardening, and rapid actuation make it a vital safeguard for military-grade generator platforms operating under extreme and unpredictable conditions.
By preventing overspeed-related failures and protecting sensitive downstream loads, the frequency relay substantially strengthens the survivability, availability, and resilience of tactical power infrastructure across combat and support missions.
Ready to learn more or place an order?
Contact Quantum Controls for detailed product specifications, expert support, and secure ordering options. Our team is ready to assist you in selecting the right protection solutions for your critical power systems.