Basler Electric RA-70-MDCT7 – Fully Controlled Three‑Phase Rectifier
The Basler Electric RA-70-MDCT7 (model also referenced as RA70MDCT7) is a high‑power, three‑phase fully controlled bridge rectifier assembly that converts AC power into controlled DC output. It is primarily used in large generator excitation systems and DC motor drives, where precise voltage regulation and high current capability are required.
Construction and Rating
The assembly consists of six thyristor (SCR) modules mounted on a robust heat sink, along with gate drive and snubber circuits. The design allows for continuous DC current output up to 70 A, with a peak repetitive reverse voltage of 1200 V. An integrated cooling fan ensures efficient heat dissipation, while the rugged housing protects against environmental contaminants. The unit is designed for chassis mounting inside a control cabinet.
Input voltage: 3‑phase, 200–600 V AC
Output DC current: 70 A continuous (100 A surge)
Output voltage: variable, depending on firing angle and input
Thyristor module: 1200 V, 70 A (average), with isolated base
Control signal: 0–10 V DC or 4–20 mA for firing angle
Cooling: forced air (integral fan), temperature switch
Protection: overcurrent detection, dV/dt snubber
Dimensions: 300 x 200 x 150 mm, weight approx. 5 kg
Application in Excitation Systems
In generator excitation, the RA-70-MDCT7 serves as the main power converter, supplying the rotor field winding with controlled DC. The firing pulses are derived from a voltage regulator (e.g., Basler DECS or SSR), which adjusts the thyristor conduction angle to maintain terminal voltage. This rectifier is suitable for both brushless and static excitation arrangements.
Installation and Maintenance
Mounting is via four screws, and connections are made through heavy‑duty bus bars or terminal blocks. Gate drive signals are supplied via a ribbon cable or twisted‑pair wires. Routine maintenance includes checking fan operation and inspecting for dust accumulation. The thyristor modules are replaceable individually, minimizing downtime.
Reliability and Standards
Built with high‑grade semiconductor devices and engineered for continuous duty, the RA-70-MDCT7 complies with IEC 60146 and UL 508 standards for power conversion equipment. Basler’s rigorous testing ensures stable performance over a wide temperature and load range. This rectifier assembly is a dependable choice for demanding industrial applications.
In summary, the Basler Electric RA-70-MDCT7 rectifier offers robust, controlled DC power for generator excitation and motor drives, backed by reliable construction and thermal management.
