Motor-generator sets 10–25 000 kVA: frequency conversion 25–1200 Hz, load isolation, transformer testing
Motor-generator sets from 10 to 25 000 kVA and above, in which an electric motor drives a synchronous generator. They galvanically isolate sensitive loads from the network, convert frequency and supply transformer test stations. The sets are produced at the plant in Mankato, USA.
- Power
- 10–25 000 kVA and above
- Input
- 50 or 60 Hz; optional motor with frequency converter
- Output
- 50, 60, 400 Hz standard; 25–1200 Hz on request; adjustable frequency
- Design
- common shaft, common or twin enclosure, brushless exciters, optional PMG, pony motor
Price, availability and lead time on request. We help with analogue selection, customs clearance and delivery.
Description
With an input frequency of 50 or 60 Hz, output frequencies of 50, 60 or 400 Hz are available as standard. In custom systems the output is fixed in the range from 25 to 1200 Hz, or it is continuously adjustable when the motor is powered from a frequency converter. Network isolation is used for computer and other sensitive electrical systems.
The motor and the generator are placed in a common enclosure or in two enclosures joined by an adapter. The rotors of both machines sit on a common shaft, so couplings, alignment, gearboxes and belts are absent on horizontal single-shaft sets. Brushless exciters are located at the shaft ends or paired at one end, and a permanent magnet pilot exciter is optional. The fan is placed between the rotors or at one end, and some models have a run-up “pony motor”. The stator and rotor windings are VPI impregnated, and the damper bars are soldered to the short-circuit rings.
The generator is built to NEMA and withstands short circuits and overloads: the continuous short-circuit current is 300% of rated for 10 s. Total harmonic distortion of the line voltage is up to 1%. The neutral is usually not connected, so the third harmonic is practically absent under balanced load, and the chosen coil pitch and skew suppress the fifth, seventh and slot harmonics. High voltage formed windings make it possible to simplify the circuit or do without an input or output transformer. Service life to overhaul is 100 000 hours, and the input power factor is 1.0 without compensation. The set is usually supplied with a control cabinet on a programmable controller, which houses the motor starter, output breaker, metering, protective relaying, voltage regulator, and manual and automatic synchronising.
Several schemes are used for measuring no-load losses and heating tests of transformers. These are sets of 1500/1800 rpm for 50–50 or 60–60 Hz, 600 rpm for 50–60 or 60–50 Hz, with adjustable frequency 50–60 Hz, and combinations of generators at 50–60 and 100–200 Hz on one motor. For induced voltage tests 90–400 Hz is used, usually 150 or 180 Hz, with low distortion and a low partial discharge level. The generator operates stably at leading and lagging power factor. The sets are used at factories and transformer test centres, for frequency conversion, for 400 Hz ground power supply and for isolating critical loads.
Technical specifications
| Power | 10–25 000 kVA and above |
|---|---|
| Input | 50 or 60 Hz; optional motor with frequency converter |
| Output | 50, 60, 400 Hz standard; 25–1200 Hz on request; adjustable frequency |
| Design | common shaft, common or twin enclosure, brushless exciters, optional PMG, pony motor |
| Voltage quality | THD up to 1% (line) |
| Overload capacity | 300% of rated current for 10 s |
| Service life | 100 000 h to overhaul |
| Input power factor (cos φ) | 1.0 |
| Transformer testing | no-load and heating at 50/60 Hz; induced voltage at 90–400 Hz, low partial discharge |
| Control | PLC cabinet: starter, breaker, metering, protection, AVR, synchronising |
Request a price and lead time
Motor-generator sets 10–25 000 kVA: frequency conversion 25–1200 Hz, load isolation, transformer testing. We reply within one business day.
Or email sales@usk.ua or call 044 339-50-20.
Questions and answers
What output frequencies can the motor-generator sets have?
As standard 50, 60 or 400 Hz with a 50 or 60 Hz input. In custom systems a fixed frequency from 25 to 1200 Hz, or adjustment through the motor's frequency converter.
What are the service life and overload capacity of the set?
Service life to overhaul is 100 000 hours. The generator's continuous short-circuit current is 300% of rated for 10 s.
Which set is needed for induced voltage tests of transformers?
Generators at 90–400 Hz, usually 150 or 180 Hz, with low distortion and a low partial discharge level. They are often combined on one motor with a 50 or 60 Hz generator for no-load tests.
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