AVR Cross Reference Guide: R230, R250, AVR328, SE350, AS440 and Common Interchange
The automatic voltage regulator (AVR) is the most frequently replaced electrical component on a generator alternator. The AVR senses the alternator output voltage, compares it with the reference setting, and adjusts the exciter field current to hold the voltage stable under changing load. When an AVR fails, the alternator output becomes unstable, the voltage may collapse, or the protection trips, and the generator cannot supply the load. Because so many AVR models are installed on generator sets worldwide, the service engineer and the parts buyer need a reliable cross-reference to identify the correct replacement, determine which models are interchangeable, and source the part quickly. This guide provides a practical AVR cross reference covering the most common models: R230, R250, AVR328, SE350, AS440, SX440, DVR2000, and the equivalent units from major manufacturers.
The tables in this guide list the common AVR models, their specifications, the alternator brands they fit, and the interchange relationships. The installer must always verify the alternator model, the excitation system, the voltage and frequency range, and the sensing configuration before replacing an AVR, because a mismatched AVR can damage the alternator or fail to regulate.
Understanding AVR Types and Specifications
AVRs are classified by three main characteristics: the excitation input type, the sensing configuration, and the control output. The excitation input is either self-excited (power taken from the main terminals) or PMG (power from a permanent magnet generator). The sensing configuration is single-phase, three-phase, or RMS sensing, and it determines the voltage range that the AVR can measure. The control output is the DC field current supplied to the exciter stator, rated in amps at a given voltage. The AVR must match the alternator’s excitation requirements, and the interchange must preserve the correct excitation input type, sensing range, and field current rating.
The most common AVRs in the industry can be grouped into three families: the Chinese AVR family (R230, R250, R448, R450, AVR328, and the equivalent WUXI/STAMFORD-style units), the Leroy-Somer family (R230, R250, R448, R450, and the newer DSR/DVR series), and the Stamford family (AS440, AS480, SX440, MX321, and SE350 in the Marathon configuration). The R230 and R250 are among the most widely copied AVRs in the world, and the AVR328 is a common equivalent for small alternators in Chinese-made generator sets.
Main AVR Cross Reference Table
The following table shows the most common AVR models and their interchange relationships:
| AVR Model | Excitation Type | Sensing | Typical Alternator / Application | Common Equivalent Models |
|---|---|---|---|---|
| R230 (Leroy-Somer style) | Self-excited | 3-phase sensing (or 1-phase by connection) | Leroy-Somer and Chinese alternators, 5-50 kVA | R230 clone, AVR-R230, SX440 (similar class) |
| R250 (Leroy-Somer style) | Self-excited | 3-phase / 1-phase | Leroy-Somer and Chinese alternators, 10-100 kVA | R250 clone, AVR-R250, SX460 (similar class) |
| AVR328 | Self-excited | 1-phase sensing | Small Chinese alternators, 5-40 kVA | AVR328A, EA16A, R-448 (small frame) |
| R448 / R449 | Self-excited | 3-phase | Medium alternators, 30-200 kVA | R448A, R449, AVR448 |
| R450 / R450T | Self-excited | 3-phase / 1-phase | Medium alternators, 50-300 kVA | R450A, AVR450 |
| AS440 (Stamford) | Self-excited | 4-wire sensing | Stamford BC16-UCDI274, 10-100 kVA | SE350, SX440 (functional equivalent) |
| SX440 / SX460 (Stamford) | Self-excited | 3-phase | Stamford UCI-UCDI, Leroy-Somer | R448/R450 class, SE350 |
| SE350 (Marathon) | Self-excited | Single-phase / 3-phase sensing options | Marathon 242-482, Stamford small frames | AS440, SX440 (functional equivalent) |
| MX321 / AS480 (PMG) | PMG | 3-phase sensing | Stamford HC4-LVI6, large frames | DVR2000, DSR series (PMG) |
| DVR2000 (Marathon digital) | PMG / self-excited option | Digital, 3-phase | Marathon 542-843, digital upgrade | MX321 class (PMG) |
The R230, R250, and AVR328 are the most commonly interchanged models in the field, because the Chinese alternator industry produces thousands of units with these AVRs, and the replacement units are widely available as OEM and aftermarket parts. The AVR supplier channel provides the full range with specification verification.
R230 and R250 Specification and Interchange
The R230 and R250 AVRs are self-excited regulators used on Leroy-Somer style alternators and their Chinese equivalents. The R230 provides a field current of up to about 3.5 A at 90 V DC, suitable for small alternators, while the R250 provides up to about 6 A at 90 V DC for larger frames. Both support single-phase or three-phase sensing by connection, and the voltage adjustment range covers 190-460 V AC. The interchange between the R230 and R250 is limited: the R250 can often be used on a smaller alternator, but the R230 should not be used on a larger alternator that requires more field current. The table below summarizes the key specifications:
| Specification | R230 | R250 | AVR328 |
|---|---|---|---|
| Input voltage (sensing) | 190-460 VAC (3-phase) / 110-260 VAC (1-phase) | 190-460 VAC (3-phase) / 110-260 VAC (1-phase) | 100-260 VAC (1-phase) |
| Frequency range | 50/60 Hz | 50/60 Hz | 50/60 Hz |
| Field output | Up to 3.5 A DC @ 90 V | Up to 6 A DC @ 90 V | Up to 3 A DC @ 75 V |
| Regulation | ±1% | ±1% | ±1% |
| Typical alternator frame | Small (5-50 kVA) | Medium (10-100 kVA) | Small (5-40 kVA) |
When interchanging an R230 with an AVR328, the installer must verify the sensing connection (the AVR328 is typically single-phase sensing) and the field current requirement. When interchanging an R230 with an R250, the field current capacity and the terminal layout must be verified. The replacement should be a certified equivalent with the same terminal functions and mounting holes.
Stamford, Marathon and Leroy-Somer AVR Interchange
The Stamford AS440, the Marathon SE350, and the Leroy-Somer R450 are the three most common self-excited AVRs in the international market, and the interchange between them is possible when the sensing voltage, the frequency, and the field current match. The AS440 is a 4-wire sensing AVR with a compact terminal block, the SE350 offers single-phase or three-phase sensing options with a trimmer adjustment, and the R450 provides a higher field current for larger alternators. The interchange table below shows the practical combinations:
| From (Original) | To (Replacement) | Conditions for Interchange | Wiring Note |
|---|---|---|---|
| AS440 | SE350 | Same alternator size; verify sensing voltage and field current | Terminal functions differ; remap terminals |
| AS440 | SX440 | Three-phase sensing required; verify range | SX440 senses 3-phase; AS440 uses 4-wire sensing |
| SE350 | AS440 | Same application; verify 4-wire sensing connection | AS440 requires the 4-wire sensing harness |
| R250 | AS440 / SE350 | Verify field current and sensing range | R250 uses 3-phase/1-phase sensing; adapt harness |
| R448 / R450 | SX440 / SE350 (large) | Verify the field current requirement | Large alternators need a higher field current AVR |
The terminal layout and the sensing connection are different across the brands, so the replacement requires a wiring adaptation and a configuration check. The AVR should be set to the correct voltage and frequency before the generator is loaded, and the output voltage should be verified at no load and under load. The Stamford AVR channel and the universal AVR channel provide the AVRs and the wiring support.
PMG AVR Interchange: AS480, MX321, DVR2000 and DSR
PMG (permanent magnet generator) systems use a separate PMG stator to supply the AVR, providing stable excitation even under heavy load transients. The PMG AVRs include the Stamford AS480 and MX321, the Marathon DVR2000, and the Leroy-Somer DSR series. The interchange between PMG AVRs is limited by the PMG output voltage and frequency, the AVR input requirements, and the field current capacity. The table below summarizes the common PMG AVR interchange:
| From (Original) | To (Replacement) | Conditions for Interchange | Notes |
|---|---|---|---|
| MX321 | DVR2000 | Verify PMG voltage (typically 170-220 VAC) and field current | Digital AVR adds programmable features |
| AS480 | MX321 | Same alternator frame; verify sensing and PMG input | MX321 adds auto start and higher capability |
| MX321 | DSR (Leroy-Somer) | Verify PMG connection and voltage range | Adapt the harness to the DSR terminal layout |
| DVR2000 | MX321 (analog) | Verify the control inputs and droop option | Digital-to-analog replacement requires reconfiguration |
PMG AVR replacement requires careful verification of the PMG output, because an incorrect input voltage or frequency damages the AVR. The digital AVRs (DVR2000, DSR) offer advanced features such as droop adjustment, soft start, and communication, but they also require a programming step before commissioning. The service engineer should request the AVR manual and the alternator data from the supplier before the replacement.
How to Select the Correct AVR
To select the correct AVR, follow these steps. First, identify the alternator manufacturer, model, and serial number from the nameplate. Second, identify the excitation system (self-excited or PMG) from the alternator manual or the connection diagram. Third, measure or record the sensing voltage, the frequency (50 or 60 Hz), and the required field current. Fourth, compare the specification with the candidate AVR models in the cross-reference table. Fifth, verify the terminal functions and the mounting dimensions. Sixth, select the replacement AVR and the required harness or mounting kit. For critical applications, use the OEM AVR or a certified equivalent with a test report, and confirm the warranty with the supplier.
The governor actuator and the AVR are often replaced together during a control system upgrade, and the supplier should provide the complete control package with the wiring documentation. The alternator parts, including the speed sensor and the rectifier kit, are also commonly ordered with the AVR to complete the repair.
Common AVR Failure Symptoms and Replacement Checks
The common symptoms of an AVR failure include voltage instability, voltage collapse under load, overvoltage, low voltage at no load, and the failure of the generator to build voltage. Before replacing the AVR, the service engineer should check the alternator wiring, the excitation components, the rotating rectifier, the brushes (if any), and the generator speed, because a faulty rectifier or a loose connection produces the same symptoms as a failed AVR. The table below lists the common symptoms and the checks:
| Symptom | Possible Cause | Check |
|---|---|---|
| No voltage build-up | Failed AVR, residual magnetism lost, open field circuit | Check AVR supply, field wiring, residual magnetism (flash the field) |
| Low voltage at no load | AVR setting, sensing voltage mismatch | Verify the sensing connection and the voltage adjustment |
| Voltage collapse under load | AVR field capacity, rectifier failure, PMG fault | Test the rectifier, the PMG output, and the AVR output |
| Overvoltage | AVR failure, sensing loss | Verify the sensing circuit and replace the AVR |
| Intermittent voltage | Loose connections, damaged harness | Inspect the connectors and the AVR terminals |
After the AVR replacement, the generator should be tested at no load, at 25%, 50%, 75%, and 100% of the rated load, with the voltage and frequency recorded at each step. The AVR’s voltage trim, stability, and droop settings should be adjusted according to the alternator manual, and the protection settings should be verified.
Sourcing B2B AVRs and Alternator Parts
AVRs are sourced by generator service companies, panel builders, and distributor networks, and the supply channel should provide verified models, quality documentation, and fast dispatch. The buyer should specify the alternator model, the excitation type, the voltage and frequency, and the required field current, and the supplier should confirm the correct AVR model and the equivalent options. The supplier should provide the test report for the AVR, the wiring documentation, and the warranty. For mixed fleets, a supplier with the full range of R230/R250/AVR328/SE350/AS440/SX440/MX321/DVR2000 and the alternator spare parts simplifies the inventory. The generator spare parts supplier can consolidate the AVR, the rectifier kit, the sensors, and the engine parts in a single shipment with the export documentation.
How to Select the Right AVR for Your Alternator
The selection of the correct AVR starts with the alternator identification. The nameplate lists the alternator model, the serial number, the voltage code, and the excitation type, and the alternator manual provides the winding configuration and the AVR specification. The AVR must match the excitation system: a self-excited alternator requires a self-excited AVR such as the R230, R250, SE350, or AS440, while a PMG alternator requires a PMG-rated AVR such as the AS480, MX321, or the DVR series. The voltage sensing range must cover the generator output voltage, the frequency range must match the 50 or 60 Hz system, and the excitation output must be adequate for the alternator frame. The AVR supply channel provides the cross-reference and the specification for the popular models.
The physical fit and the wiring are the next step. The AVR mounting, the connector layout, and the terminal functions should be compared with the original unit, and the harness should be adapted where necessary. The installer should verify the sensing connection (single-phase or three-phase), the droop CT connection for the parallel operation, and the stability adjustment range. The Stamford AVR supply channel covers the Stamford models and the certified equivalents, and the same verification applies to the Marathon, Leroy-Somer, and Mecc Alte units.
AVR Troubleshooting and Common Failure Modes
The common AVR failure modes include the no-output failure, the output drift, the instability, and the failure under load. The no-output failure is often caused by an open input fuse, a failed power stage, or a disconnected excitation wire; the output drift is often caused by a failed sensing circuit or a loose voltage adjust potentiometer; the instability is often caused by a faulty stability capacitor, a wrong frequency setting, or an oscillation in the excitation circuit; and the failure under load is often caused by an overloaded AVR, a failing rectifier diode, or a shorted rotor. The troubleshooting should measure the input voltage, the sensing voltage, and the excitation output at each stage, and the measurements should be compared with the alternator manual.
The replacement should follow the verified procedure: the engine is stopped, the battery is disconnected, the AVR is removed with the harness marked, and the new unit is installed with the correct sensing and excitation connections. After the start, the output voltage is adjusted, the stability is checked from no load to full load, and the speed sensor and the governor are verified for the frequency stability. The battery charger and the battery condition should also be verified, because a failing battery can cause the voltage instability that is wrongly attributed to the AVR. The generator spare parts supplier should provide the technical support and the test documentation for the replacement.
AVR Cross Reference Database and Certification
The reliable cross-reference of the AVRs depends on the database quality, and the B2B buyer should verify that the cross-reference comes from the manufacturer data, the alternator builder data, or the tested equivalence, not from the copied marketing tables. The cross-reference database should record the alternator model, the voltage code, the excitation type, the sensing configuration, the frequency range, the excitation output, the mounting, and the connector layout for each AVR, and the database should be updated when the alternator builder releases the new specification. The buyer should request the cross-reference certificate for the critical AVRs: the certificate should confirm the electrical specification, the test result, and the warranty for the interchange, and should be valid for the specific alternator application.
The certification and the quality control are the key differentiators in the aftermarket AVR market. The certified AVR should be tested at the rated voltage and frequency, the excitation output should be verified against the alternator field requirement, and the stability should be tested with the representative alternator load. The supplier should provide the test report with the measured values, the batch number, and the date, and should offer the replacement warranty for the manufacturing defects. The AVR supplier should also provide the technical support for the installation, the configuration, and the troubleshooting, and the support should cover the cross-brand and the cross-model applications.
The buyer should compare the price and the delivery of the certified AVR against the OEM unit: the certified aftermarket unit should offer the comparable quality at the lower price, but the critical applications such as the hospitals, the data centers, and the process plants may require the OEM part by the specification. The Stamford AVR supply channel provides the original and the certified units for the Stamford alternators, and the generator spare parts supplier consolidates the AVR with the rectifier kits, the speed sensors, and the engine parts for the complete service order. The ordering should include the alternator model and the serial number, the voltage code, and the required documents, so the supplier can confirm the correct AVR and the delivery time.