Automatic Healthy Phase Selectors (PEF series)

Novatek Electro India’s PEF series (such as the PEF-301, PEF-319, and PEF-320) consists of microprocessor-based automatic phase selectors. These devices are designed to maintain an uninterrupted power supply to a single-phase load by monitoring a three-phase network and selecting the “healthiest” phase.

How It Works: The Selection Logic

The PEF series operates on a Priority-Based Selection system. The device is connected to all three phases (L1, L2, L3) and a Neutral (N).

1. Continuous Monitoring: The internal microcontroller simultaneously measures the voltage levels of all three incoming phases.
2. Health Check: It compares these levels against user-defined thresholds for Minimum (U_{min}) and Maximum (U_{max}) voltage.
3. Priority Connection: Under normal conditions, the device defaults to Phase L1 (the priority phase).
4. Automatic Switching:
   • If L1 fails or its voltage goes out of bounds, the device instantly checks L2. If L2 is healthy, it switches the load there within < 0.2 seconds.
   • If L2 is also faulty, it moves to L3.
   • If all phases are “unhealthy,” the device disconnects the load entirely to prevent equipment damage.
5. Return to Priority: Once the voltage on L1 stabilizes, the device waits for a user-set “Return Delay” (Tr) before switching back from a reserve phase to the priority phase.

Key Features

• Microprocessor Control: Unlike analog selectors, the PEF series uses digital logic for precise voltage sensing and faster switching.
• Dual-Threshold Protection: Users can manually set both upper and lower voltage limits via front-panel potentiometers.
• High Current Capacity: PEF-301: Supports up to 16A (approx. 3.6 kW) direct load or any load by using external magnetic contactors.
  • PEF-319: Supports up to 30A (approx. 6.6 kW) direct load or any load by using external magnetic contactors.
• External Contactor Support: For industrial loads exceeding their direct rating, the units can act as a controller for external magnetic starters/contactors.
• Adjustable Timing: T{on} (Start/Reclosing Delay): Protects compressors (like ACs or fridges) by preventing immediate restarts after a power flicker.
  • Tr (Return Delay): Prevents “hunting” (frequent switching) when a priority phase is unstable.
• Anti-Sticking Protection: High-end models (like PEF-301 & PEF-319) monitor internal relays to ensure they haven’t “welded” shut, preventing phase-to-phase short circuits, which also acts as electrical interlock while using external contactors.

How it Differs from Traditional Selectors

Traditional phase selectors are often manual rotary switches or simple relay-based “dumb” circuits. Here is how the Novatek PEF series stands out:

 Summary Table: Popular PEF Models