Overview
The General Electric 12IAC66B4A is a Type IAC electromechanical time overcurrent relay built for protection coordination in industrial power systems and switchgear installations. This proven design combines adjustable time-delay characteristics with instantaneous and time-overcurrent pickup settings, making it suitable for backup protection schemes and feeder protection applications in facilities requiring selective coordination.
Key Features
- Type IAC design with proven electromechanical operation
- Adjustable time-overcurrent (TOC) range: 4–8A
- Adjustable instantaneous overcurrent (IOC) range: 20–80A
- Time-delay dial settings for coordination with other protective devices
- Compact form factor suitable for retrofit into existing relay panels
- Field-adjustable current taps for application flexibility
Technical Specifications
This relay features a robust electromechanical design typical of legacy GE protective relays used in medium-voltage switchgear. The nameplate-rated pickup current can be adjusted via tap selection, and the operating time is controlled by a time-dial adjustment. The relay contacts provide the output signal to trip or alarm circuits downstream.
Typical Applications
- Feeder and transformer protection in industrial substations
- Backup protection in medium-voltage networks
- Coordination with fuses and other protective devices
- Retrofit and replacement in legacy control panels
- Switchgear control circuits requiring selective time-delay
Compatibility & Replacements
Compatible With
- GE Magne-Blast and other medium-voltage switchgear platforms
- Legacy industrial power distribution and control systems
- DC or AC coil energization (verify coil voltage for your application)
- Electromechanical protection relay schemes
Replaces / Drop-In Replacement For
The 12IAC66B4A is a direct replacement for identical Type IAC relays in GE switchgear. Verify your existing relay’s nameplate rating and current-tap settings before ordering. Interchangeability with other IAC variants (66A, 66C) depends on coil voltage and current ranges; consult your control panel documentation or system integrator.
Works With
- Electromechanical relay control and monitoring systems
- AC and DC trip coils (standard industrial voltages)
- Mechanical time-delay coordination schemes
- Switchgear control wiring and protection logic
