1. General Information

• Model Number: 0-52806-1 (also 0528061, 0-52806-01)

• Brand: RELIANCE Electric (later ABB Baldor-Reliance)

• Product Category: Industrial DC Drive Safety Protection Board (Plug‑in Control Card)

• Alias: TLOA (Tach Loss/Overspeed) Board, TLOB Board, Speed Monitoring Protection Card

• Description: Rack‑mounted plug‑in PCB with conformal coating, gold‑plated edge connector, front‑panel indicators and calibration potentiometer

• Status: Obsolete (legacy OEM part; available as refurbished/used stock)

• NSN: 5998‑01‑217‑1441

2. Function & Operating Principle

• Primary Function: Dedicated speed safety protection for Reliance DC drive systems

• Core Functions:

  • Tachometer Loss Detection: Continuously monitors tachometer generator (tach) signal; triggers alarm/trip on signal loss

  • Overspeed Protection: Compares actual speed to reference; trips on over‑speed threshold (prevents motor “runaway”)

  • Fault Indication: Front‑panel LEDs for Tach Loss and Overspeed; reset button for fault clearing

  • Calibration: Onboard potentiometer (“Tach Calibration”) for tach signal scaling adjustment

• Role: Final safety barrier in speed loop; protects drive and load from speed‑feedback faults

3. Technical Specifications

3.1 Electrical

• Monitoring Signal: AC tachometer generator voltage/frequency signal

• Signal Input: 1‑phase tach signal (typical 0–100 VAC, 50/60 Hz)

• Output Contacts: Relay output for fault alarm/trip (SPDT, rated for control‑circuit voltage)

• Power Supply: 115/230 VAC (drive internal supply)

• Power Consumption: ≤ 15 VA

3.2 Environmental

• Operating Temperature: 0 °C to +55 °C

• Storage Temperature: −20 °C to +70 °C

• Relative Humidity: 5%–95% (non‑condensing)

• Vibration Resistance: 0.15 mm (10–55 Hz)

• Protection Class: Conformal coated PCB (moisture, dust, chemical resistance)

3.3 Mechanical

• Form Factor: Standard 19” rack plug‑in card

• Dimensions (W × H × D): 120 mm × 220 mm × 30 mm

• Weight: ~1.4 kg (3 lb)

• Connector: Gold‑plated edge connector (backplane interface)

• Front Panel: 12‑position terminal strip, 2 LEDs, 1 reset button, 1 calibration pot, 2 locking screws

3.4 Performance

• Response Time: Millisecond‑level fault detection & trip

• Trip Accuracy: ±2% of calibrated speed setpoint

• Repeatability: ±1% (stable over temperature range)

• EMI Immunity: Compliant with industrial drive EMC standards

4. Circuit Configuration (Key Components)

• Transformer: TR‑12174 (411027‑5‑R)

• Relay: 1 × SPDT fault relay

• Semiconductors: 6 × ICs, 6 × transistors, diodes

• Passives: Disk capacitors, polyester capacitors, metal‑film resistors

• Connectors: Edge connector, 12‑position terminal block, calibration pot header

5. Compatibility & Applications

5.1 Compatible Drives

• Reliance MaxPak Plus DC Drives

• Reliance V‑Series DC Drives

• Reliance Legacy DC Motor Control Systems

5.2 Industrial Fields

• Metallurgy: Rolling mills, continuous casters

• Paper & Textile: High‑speed web processing lines

• Chemical & Water Treatment: Pump/fan speed control

• Material Handling: Cranes, conveyors, port equipment

• Legacy Equipment: Retrofit/replacement for aging Reliance DC drive systems

6. Installation & Maintenance

• Mounting: Direct plug‑in into drive backplane; secure with front‑panel locking screws

• Wiring: Tach signal to terminal block; fault output to drive control circuit

• Calibration: Adjust “Tach Cal” pot for correct speed scaling (per drive manual)

• Maintenance: Inspect connectors annually; clean conformal coated surface; test relay & LEDs periodically

7. Ordering Information

• Part Number: 0-52806-1

• Alternative Part Numbers: 0-52806-01, 0528061

• Replacement: Direct replacement for 0-52806 (non‑1 suffix)