Excitation faults rarely announce themselves until they cause a trip. A failed diode or a drifting AVR can push a set into overexcitation or loss of field, trip it off the bus and overload the others. The risks are an outage, damaged equipment on your site and failed tests when gas turbine units later join the same bus and must share reactive load with your gensets.
USP&E Helps You Keep the Voltage Steady
We know you want stable voltage and gensets that share load evenly. USP&E has delivered 150+ power projects in 45+ countries, with 25,000 MW contracted since 2002, and our 400+ engineers and project managers test, repair and run gensets and gas turbines on shared buses. USP&E is independent and is not a Caterpillar dealer. Our systems are ISO 9001 and ISO 45001 certified, and every deal runs under FCPA and OFAC controls. USP&E is a full-service EPC and O&M contractor, not a broker.
You do not need to replace your alternators to fix unstable voltage. You need readings under load, a check of the settings, tests of the exciter and diodes, and a plan for how future gas turbine units will share the job.
Record Voltage and Reactive Load Under Real Load
Start with readings, not guesses. Record voltage, current, real and reactive load, power factor and excitation current or voltage on each set while it carries normal load, and again during a large motor start. A set that sags far more than its neighbours, recovers slowly or hunts around its setpoint has an AVR or excitation issue worth chasing.
When sets run in parallel, look at reactive load sharing. Sets of the same size should share reactive load roughly in proportion. If one set carries most of it, its AVR settings, droop or reactive compensation may be wrong, or its sensing may be faulty. Uneven sharing heats the overloaded alternator and can trip it on overexcitation protection.
Compare today’s settings with the commissioning record. Settings often change during repairs and are never written down. A clear record of the settings each set should have is the first tool you need, and our natural gas gensets in stock ship with that record for the same reason.
Test the Exciter, Diodes and AVR
During a planned outage, test the exciter stator and rotor windings for insulation resistance and continuity. Test each rotating diode and the surge suppressor. A single failed diode can cause high excitation current, heating and voltage ripple, and a second failure can follow quickly. Replace diodes as a matched set when you find a fault.
Check the AVR itself: sensing wiring, power supply, setpoints, gain and stability settings, under-frequency roll-off and any limiters. Check that the voltage sensing is wired to the right phases and that the protection for overexcitation and loss of field is set and tested. After any repair, run the set on load and record the new settings before it goes back into service.
Fit these checks into the wider electrical plan. The balance-of-plant electrical scope covers switchgear, protection and cabling, and your AVR tests should match the protection settings that scope defines.
Plan How Gas Turbine Generators Will Share the Bus
When gas turbine generators join a bus that your gensets already serve, they bring larger alternators with their own excitation systems. Plan how reactive load will be shared, which units will control voltage, and how the station control system will coordinate them. Check whether your genset AVRs need new settings or upgrades so they work with the turbine units rather than against them.
The same planning applies whether you add used/new gas turbines, a remanufactured GE Frame 6B or natural gas engines/stations. Data centre campuses face it at larger scale under hyperscale EPC/O&M, where AI gas turbines, hyperscale generators and gas turbines for compute share buses, and New USP&E FX-45 45MW Modular Gas Turbine for the Hyperscale Data Center sector in the USA will be planned with reactive sharing in mind. Read more on gas turbine plant design.
Until the turbines arrive, keep your genset excitation healthy and well recorded. Our sister site covers Cat-class engine care and the path to turbines, from cooling to combustion.
Global Offices Behind Your Cat Genset Programme
Your plant does not run on head-office time. USP&E anchors your Cat genset switchgear and GT campus expansion in Johannesburg (22 Kildoon Rd, Bryanston) and Cape Town (31 Brickfield Road, Woodstock), where engineering, project controls and commissioning support sit, close to the African sites USP&E has powered for years.
When paralleling switchgear, Cat gensets and gas turbine packages must be financed, sourced or shipped, London (162-168 Regent Street) structures contracts and finance, Colorado Springs (1755 Telstar Dr, Suite 300) and Knoxville (800 S Gay St, Suite 700) reach US equipment supply, and Wuxi, China (No. 1, Ningzhou Road, Wuxi) supports China supply chain and manufacturing.
For Cat genset voltage and excitation work, Johannesburg and Cape Town engineers test sets on African sites, while Wuxi follows up AVRs, diodes and panels sourced from China. Regions served: USA | AFRICA | UK | UAE | CHINA. One accountable team behind 150+ power projects in 45+ countries and 25,000 MW contracted since 2002, ISO 9001 and ISO 45001 certified.
What USP&E Has Delivered for Cat Genset Buyers
You want proof that USP&E can keep gensets stable on demanding networks. These projects show that record.
- USP&E supplied 28 Cummins KTA50 containerised diesel gensets, 1,275 kVA each, for Perseus Mining’s Nyanzaga Gold Project in Tanzania.
- Barrick Gold, Loulo-Gounkoto, Mali: USP&E rebuilt more than 80 MW of Caterpillar CM32 engines and added 24 MW of new zero-hour capacity, delivering a 104 MW station with 300% greater reliability and availability than previously recorded at site. Read the case study.
- Kinross Gold, Tasiast, Mauritania: USP&E supplied and installed a Caterpillar backup power station of low-hour Cat 3516B gensets with new switchgear, on time and on budget. Read the case study.
HowTo: Check Cat Genset AVR and Excitation and Plan for GT
Your 3-step plan: 1. Share voltage, reactive load and settings records for each set. 2. Receive a test plan for exciters, diodes and AVRs. 3. Fix faults, record settings and plan for gas turbine units.
- Record voltage, reactive load and excitation readings on each set under load.
- Check the AVR settings against the commissioning record and the site needs.
- Test exciter windings and rotating diodes during planned outages.
- Check reactive load sharing when sets run in parallel.
- Fix faults and record new settings after every repair.
- Plan how gas turbine generator excitation will share reactive load with your gensets.
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FAQ: Cat Genset AVR and Excitation Checks Before GT
What does the AVR do on a Cat genset?
USP&E describes the automatic voltage regulator as the controller that holds output voltage steady. It adjusts the excitation current to the alternator’s rotating field as load changes. When it drifts or its sensing fails, voltage becomes unstable and the set may trip on protection.
What are signs of a failed rotating diode?
USP&E looks for high excitation current, voltage ripple, heating in the exciter and a set that cannot hold voltage under load. A failed diode puts extra strain on the others. Testing each diode during a planned outage finds the fault before a second one fails.
Why does one genset take more reactive load than the others?
USP&E usually finds wrong AVR settings, incorrect droop or reactive compensation, or faulty voltage sensing. Uneven sharing overheats the overloaded alternator and can trip it on overexcitation. Matching settings across sets and testing them on load usually restores even sharing.
Do AVR settings change after a repair?
USP&E often finds that they do. Settings are adjusted during repairs and not written down, so the set behaves differently afterwards. Recording the correct settings for every set, and checking them after each repair on load, keeps voltage stable and sharing even.
Where are USP&E’s offices for Cat genset electrical work?
USP&E supports Cat genset electrical work in Africa from Johannesburg and Cape Town. Knoxville and Colorado Springs support US sites, London handles contracts and finance, and Wuxi follows up AVRs, diodes, control panels and other electrical parts made in China for your sets.
Has USP&E delivered genset projects with new switchgear before?
USP&E supplied and installed a Caterpillar backup power station of low-hour Cat 3516B gensets with new switchgear for Kinross Gold at Tasiast, Mauritania, on time and on budget, as a public case study shows. Barrick’s Loulo-Gounkoto station is another public example.
Is USP&E a broker or a Caterpillar dealer?
USP&E is neither a broker nor a Caterpillar dealer. USP&E is an independent EPC and O&M contractor that tests, repairs and runs gensets with its own engineers, and answers for every setting it records and every repair it makes on your site.
How fast can USP&E look at my voltage problems?
USP&E can start reviewing your readings and settings records as soon as you share them. Engineers flag likely causes first, such as diode faults or wrong settings, so the right tests, parts and people can be ready for your next planned outage.
Hold the Voltage, Share the Load
Test the excitation and your gensets hold steady voltage and share load evenly, ready for gas turbines to join. Ignore it and the next trip may take the site down. USP&E will help you test, fix and plan with confidence.
Talk to an engineer about your Cat genset switchgear and GT campus expansion: use the USP&E contact page, call +27 10 822 2324 or email info@uspeglobal.com. You can also search the USP&E inventory for equipment that fits.
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