AC alternators (synchronous generators) for generating sets · kVA rating at 50/60 Hz, continuous or standby rating and insulation class, voltage and poles, AVR and excitation, ambient and altitude de-rating, speed, enclosure and mounting
An alternator — an AC synchronous generator — converts the shaft power of an engine or turbine into AC electricity, and in a generating set it sets the kVA available, the voltage quality and how the set copes with motor starting and faults. Settle three things before choosing one: the rating and duty at your frequency and voltage, the excitation and voltage regulator the loads need, and the de-rating, speed, enclosure and mounting for the site and prime mover.
Brushless AC synchronous alternators for diesel and gas engine generating sets, turbines, marine auxiliary, combined heat and power and similar duties, from small single-bearing units to multi-megawatt machines. Vehicle charging alternators, complete generating sets, permanent-magnet wind generators and motors are outside this page; emergency generator sets have their own page.
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01
STAMFORD lists wire-wound alternators from 7.5 to 5,000 kVA for marine, oil and gas auxiliary, UPS, telecoms, combined heat and power, construction and other continuous or standby applications, with SAE adaptors for coupling to a range of prime movers; its models run from the S0 (30 kVA at 50 Hz, 36 kVA at 60 Hz) to the P80 (4,200/5,100 kVA) and S9 (4,500/5,000 kVA). [1] Its S4 lists 450 kVA continuous at 50 Hz and 560 kVA at 60 Hz across a 210–560 kVA range, 380–690 V, 4 poles, 2/3 winding pitch, IP23, Class H insulation and self-excitation, with options including PMG excitation, single or double bearings, air filters, thermistors, winding RTDs and anti-condensation heaters. [2]
Its guidance note on ratings explains that alternator ratings follow IEC 60034-22: a Basic Continuous Rating (duty type S1, unlimited hours) offered at Class H (125 °C rise over 40 °C), Class F (105 °C) and Class B (80 °C) temperature rise, and a Peak Continuous or standby rating (duty type S10) that allows a higher temperature — for low-voltage Class H, 150 °C over 40 °C or 163 °C over 27 °C — at the cost of reducing alternator life by 2 to 6 times; the life factor is marked on the rating plate. [4]
The brochure lists prime movers including diesel and gas engines and steam and gas turbines, and compatibility with CE, CSA, UL, NEMA, EN, VDE, IEC and UKCA standards, with marine classification available. [3]
Give the supplier the prime mover and coupling (SAE adaptor, single or double bearing), frequency and speed, voltage and connection, kVA and power factor, continuous or standby duty and temperature-rise class, load types (motor starting, non-linear, unbalanced), AVR and excitation, parallel operation, site ambient and altitude, enclosure and filters, sensors and heaters, standards and marine class, and quantity.
02
The STAMFORD | AvK brochure describes the automatic voltage regulator (AVR) as maintaining steady-state output voltage within close limits, encapsulated against moisture, salt and sand and on anti-vibration mounts; its AVR table runs from ±1.0% regulation (analogue self-excited AS440, AS540, AS480; MX341 with PMG) through ±0.5% (MX322, VITA 01) and ±0.25% (digital DM110, DECS 100/250) to ±0.2% (UNITROL 1010/1020). [3]
Its environmental rating note de-rates low-voltage Class H output by 3% for every 5 °C above 40 °C (0.97 at 45 °C down to 0.88 at 60 °C, the maximum permissible ambient), and by 3% for every 500 m above 1,000 m up to 4,000 m (0.97 at 1,500 m down to 0.82 at 4,000 m), with no extra output allowed below 1,000 m. [5] Its speed note says the alternators are designed for a governor running 5% above synchronous speed at no load and falling to synchronous speed at full output; in variable-speed use a 4-pole alternator has a maximum continuous speed of 1,800 rpm (±5%), with a 750 rpm minimum and 2,250 rpm overspeed for 2 minutes. [6]
Editorial calculation: a 450 kVA rating at a 50 °C, 2,000 m site becomes 450 × 0.94 × 0.94 ≈ 398 kVA if both factors are applied together; at 0.8 power factor that is about 318 kW. A 4-pole machine runs at 120 × 50 ÷ 4 = 1,500 rpm on 50 Hz and 1,800 rpm on 60 Hz. [5] [2] [6]
03
ENGGA (Yangjiang) lists N-series low-voltage, GS-series medium- and high-voltage and M-series marine AC alternators.
Ask each supplier for the datasheet for the exact core and winding, with continuous and standby ratings, efficiency, reactances, motor-starting curves, voltage regulation and de-rating factors for your site. [2] [4]
04
Each part is tied to the STAMFORD document that rates it: winding, bearings and enclosure to the S4 sheet, insulation to AGN 013, and the AVR to the Power Portfolio table.
| Part | What it controls | Fix in the order |
|---|---|---|
| Stator winding | Voltage; kVA; pitch. [2] | Winding; pitch. |
| Insulation system | Temperature rise; life. [4] | Class H/F. |
| Rotor and exciter | Excitation. [2] [3] | Self-excited; PMG. |
| AVR | Voltage regulation. [3] | ±%; digital. |
| Bearings and adaptor | Coupling to engine. [2] [1] | 1 or 2 bearings; SAE. |
| Enclosure and cooling | Protection; airflow. [2] | IP23; filters. |
05
Values are STAMFORD's, with the S4 (450/560 kVA) as the worked example; efficiency, harmonic distortion, weight and noise depend on the exact core and winding and are not given in these sources.
| Field | What it means and published values | Ask the supplier for |
|---|---|---|
| Rated Power | 7.5–5,000 kVA range; S4 450/560 kVA. [1] [2] | kVA; kW at pf. |
| Rated Voltage | 380–690 V (S4). [2] | V; connection. |
| Frequency | 50/60 Hz. [2] | Hz. |
| Efficiency | Core and winding dependent. | % at load. |
| Speed Range | Variable-speed use, 4-pole: 750 rpm minimum to 1,800 rpm (±5%) maximum continuous, 2,250 rpm overspeed for 2 minutes; fixed speed 1,500 rpm at 50 Hz and 1,800 rpm at 60 Hz. [6] | rpm. |
| Insulation Class | Class H. [2] [4] | Class; rise. |
| Protection Rating | IP23. [2] | IP; filters. |
| Ambient Temperature | 40 °C base; 60 °C max. [5] | °C; de-rate. |
| Voltage Regulation | ±1.0% to ±0.2% by AVR. [3] | AVR; ±%. |
| Total Harmonic Distortion | Waveform quality. | %. |
| Weight | Machine mass. | kg. |
| Noise Level | Machine noise. | dB(A). |
06
Paste it into your enquiry below or into an email to a maker, then replace every bracket.
Prime mover: [engine/turbine; SAE; bearings] Output: [kVA; pf; V; Hz] Duty: [continuous; standby; class] Loads: [motors; non-linear; unbalanced] AVR/excitation: [±%; PMG] Site: [°C; altitude] Enclosure/options: [IP; filters; RTDs; heaters] Quantity: [units]
1 company lists this product among what they make. Company figures are quoted from each company's own website; every card states where the relationship came from.
Its website lists N-series low-voltage, GS-series medium- and high-voltage and M-series marine AC alternators.
Product scope checked 2026-10-12
Explore company information and manufacturing capabilities, then discuss the scope of your project with a relevant supplier.
STAMFORD's AGN 013 defines continuous (S1) at Class H 125 °C rise and standby (S10) at higher temperature, cutting life 2–6 times. [4]
For low-voltage Class H output at the base continuous rating, STAMFORD de-rates 3% for every 500 m above 1,000 m, to 0.82 at 4,000 m. [5]
For low-voltage Class H output at the base continuous rating, STAMFORD de-rates 3% for every 5 °C above 40 °C, to 0.88 at 60 °C, the maximum permissible ambient. [5]
STAMFORD | AvK lists AVRs from ±1.0% (analogue) to ±0.25% and ±0.2% (digital). [3]
Sources checked 2026-10-11. STAMFORD | AvK product pages, its Power Portfolio brochure and its application guidance notes AGN 012, 013 and 041 are used to show what an alternator specification covers; values for your order must come from the supplier's datasheet for the exact machine.
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