Basler KR4F Voltage Regulator – Compact Excitation for Brushless Generators

The Basler KR4F is a cost-effective, static voltage regulator designed for brushless alternators in the 20–100 kVA range. It provides stable voltage regulation with minimal components, ensuring high reliability and easy field servicing.

Operating Principle

The KR4F uses a phase-controlled SCR bridge to supply the DC field current to the exciter stator. It samples the generator's terminal voltage via a sensing transformer and compares it to a reference. The error signal adjusts the firing angle of the SCRs, modulating the field current to maintain constant voltage.

Key Specifications

• Input Voltage: 120/240 VAC, 50/60 Hz

• Output Current: 4 A continuous, 6 A forcing

• Regulation Accuracy: ±1%

• Droop Adjustment: 0–8% for parallel operation

• Built-in under-frequency roll-off at 95% of nominal

• Operating Temperature: -30°C to +65°C

Adjustments

Three potentiometers are provided: Voltage (Vref), Stability (damping), and Droop. The stability adjustment allows the regulator to be tuned for different generator dynamic responses, preventing hunting.

Protection

The KR4F includes over-excitation limiting, which reduces the output if the field current exceeds a safe level. It also has a loss-of-sensing protection that cuts off excitation to prevent run-away voltage.

Installation

Mounting is via two screws on a flat panel. The unit is compact (approx. 150 x 100 x 60 mm) and weighs less than 1 kg. Terminal connections are pluggable for quick replacement.

Applications

Ideal for standby generators in residential, agricultural, and light commercial applications. Also used in portable generator sets where space and cost are constraints.

Maintenance

The KR4F is maintenance-free. Periodic checks of the heat sink and terminal tightness are recommended.

Compliance

Meets basic EMC requirements for residential and light industrial environments.

Conclusion

The Basler KR4F Voltage Regulator offers an economical yet dependable solution for small generator excitation, backed by Basler's quality and support.