AP4 Group – Full-Service Heavy-Duty & Aeroderivative Industrial Gas Turbine Maintenance Provider.

The Solution for Retrofitting Agin Excitation Systems

TC&E - A Division of AP4 Group offers turnkey solutions for retrofitting aging excitation systems. With the ability to upgrade most excitation control systems up to 6000 field amps, our team can evaluate your system and suggest a turnkey solution that best fits your plant's application and budget. Whether a DFE or complete system rip and replace, we will work with your team to determine the best solution for your plant.

Most often a Digital Front End Upgrade using Basler™ DECS Series AVR’s is the easiest and most economical solution. Our team has lots of experience installing Basler™ DECS AVR’s, from Hydro to Large Steam applications. TC&E - A Division of AP4 Group and Basler™ have developed a relationship that ensures quick & dependable responses from Engineering Support and Product Delivery.

In most circumstances the Exciter Bridge and SCR Components are long lasting and require very little maintenance and repair. The AVR Portions of the exciter control the voltage regulation and communications to the turbine control panel. By upgrading the AVR with a Digital Front End, you bring your Exciter back to the most modern levels of reliability and ensure safe and consistent generator control.

Upgrading to the latest Digital Technology offered by Basler™ and other AVR Manufactures ensures operational readiness and compliance with NERC & ISO Capacity reliability requirements.

Examples of Retrofit Options


GE™ 7FA EX2000 Dual Bridge upgraded with DECS 2100 DFE. Benefits are the DECS Cores are redundant as compared to EX2000 Primary and Secondary Cores. If the EX2000 main core “fails over” to the Secondary Core, the Unit cannot be started up in this condition. With the DECS2100 Redundant Core Technology, the unit would still be “ready to start”.

BASLER™ DECS 400 AVR GE 7EA/6B SCT-PPT style Exciters are typically upgraded with a DECS400 AVR system. This takes an older analog system up to the Digital Age and allows system monitoring, trending and analysis. You can add PSS and Fault Capture trending.

Smaller Steam Turbines and Hydro’s are typically upgraded with DECS250 AVR System..


Full Replacements

In most cases, a digital front end upgrade is the best option to keep excitation systems up to date and reliable. In some cases, such as brushless systems, it can be more cost effective to replace the complete excitation system. Our designers will work with your team to determine the most cost-effective solution for your upgrade needs.