⚙️ Overview: HMBK‑35 OLTC Controller (Automatic Voltage Regulator)

The HMBK‑35 is an automatic on‑load tap changer (OLTC) controller primarily used to manage voltage regulation in power transformers. It controls tap mechanisms, monitors voltage thresholds, and offers both local and remote control modes .

? Technical Features & Specifications

• Voltage Supply:

  • Standard HMBK‑35: 380 VAC (±15%)

  • HMBK‑10 variant: 220 VAC for CF‑type OLTCs

  • Frequency: 50/60 Hz 

• Scope of Application:

  • HMBK‑35 is designed for SYX (J, T) ZZ‑type tap switches.

  • HMBK‑10D is used with CF‑type OLTCs in different transformer setups 

• Tap Operation & Interface:

  • Gear position display, operation buttons (“1‑N”, “N‑1”, “Stop”)

  • Remote manual commands via inputs

  • BCD-coded position output contacts

  • Contact outputs for “on‑position” signals

  • RS‑485 (Modbus/Hm‑PT/CDT protocols) available for integration/remote control

  • Alarm/fault output contacts and interlock logic with NC input contact 

• Voltage Regulation Settings:

  • Adjustable set voltage: 80–450 VAC (1 V steps)

  • Regulation accuracy: 0.1–10.0% (0.1% steps)

  • Time‑delay for switching: 10–360 s configurable (1 s steps)

  • Compensation functions: under‑voltage (< 70%), over‑ voltage (> 30%), alarm lockout, etc. 

• Environment & Mounting:

  • Indoor installation only

  • Ambient temperature: –10 °C to +40 °C; humidity ≤85%; altitude ≤2,000 m

  • No exposure to shock, corrosive gases, or moisture

  • Rated for typical substation/control room installation conditions 

✅ Why It Matters

• Seamless integration for automated voltage control in transformer tap changers.

• Offers local and remote operation, via push buttons or RS‑485 network control.

• BCD output and contact signaling enable easy PLC/SCADA integration.

• Adjustable regulation thresholds and timing settings offer precise voltage management.

• Built-in alarms and blocking features safeguard misoperation or fault conditions.

? Summary Table