Frequency converters and UPS for defence and aerospace
400 Hz ground power, frequency conversion for test benches, and supplies specified against MIL-STD-704 rather than a catalogue.
What actually goes wrong
Aircraft systems run at 400 Hz because a transformer at that frequency needs roughly an eighth of the core mass it would at 50 Hz. Everything on the ground that touches those systems — hangar power, MRO benches, avionics test rigs — has to match, and the tolerances are set by military standards rather than by commercial practice.
What to get right
The decisions on this list are the ones that are expensive to change after the equipment is on site.
MIL-STD-704 compliance
Voltage, frequency, distortion and transient response specified against the standard, with test reports issued for the actual unit supplied.
Fixed or mobile GPU
Trolley-mounted ground power units with the aircraft connector and cable fitted, or fixed hangar installations with pit outlets.
Test bench supplies
Programmable voltage and frequency for qualification testing across the full operating envelope, not just at nominal.
Documentation
Type test reports, factory acceptance test protocols and traceable calibration certificates. Scope this at enquiry stage.
Environmental spec
Extended temperature range, humidity, vibration and EMI/EMC to the applicable standard.
Long-term supportability
Spares availability and repairability over a service life measured in decades, not years.
What we supply into this sector
Static Frequency Converter
Run 60 Hz equipment on a 50 Hz supply — or generate a clean 400 Hz for aviation ground power — with no rotating parts and no maintenance schedule.
Online UPS
True double-conversion topology from 3 kVA to 200 kVA across three series, with single-phase or three-phase output. Zero transfer time, pure sine output held to ±1%, and up to 96% efficiency. Built and load-tested in Pune.
Isolation Transformer
Galvanic separation between supply and load, with electrostatic shielding that attenuates common-mode noise by 100 dB or better. 1 kVA to 500 kVA.
Industrial Battery Charger
SMPS chargers from 5 A to 30 A and float-cum-boost chargers from 5 A to 200 A, sized to the bank rather than to a catalogue number.
Through the life of the machine
Questions we get asked
Anything not covered here, call us — most of it is faster to answer on the phone.
01Do you supply 400 Hz ground power units?
Yes, from 15 to 200 kVA, as fixed hangar installations or trolley-mounted mobile GPUs with the aircraft connector and cable fitted. Output is 115/200 V three-phase at 400 Hz with frequency stability of ±0.01%.
02Can you meet MIL-STD-704 output requirements?
Yes — voltage regulation, frequency stability, distortion and transient response are specified and tested against it. Tell us the applicable revision at the enquiry stage, because the limits differ between revisions and it affects the design, not just the paperwork.
03Why does aerospace ground equipment run at 400 Hz?
Because aircraft systems do. Higher frequency allows transformers, motors and generators to be much smaller and lighter for the same power, which matters enormously in an airframe — so aircraft standardised on 400 Hz and ground support has to match it. Supplying an aircraft or testing its systems on the ground therefore needs a converter from the 50 Hz mains, not a transformer.
04What is a static frequency converter, and how is it different from a motor-generator set?
Both convert one frequency to another; only one of them has moving parts. A motor-generator does it mechanically, with the wear, noise, foundation and maintenance that implies. A static frequency converter rectifies to DC and synthesises the output electronically, so it is quieter, more efficient, needs no rotating maintenance and can hold tighter output regulation. It is the reason most new ground installations are static.
05Can one converter supply both 60 Hz and 400 Hz?
Usually not from the same output at the same time, and the requirement should be stated at enquiry rather than assumed. Output frequency, voltage and phase configuration are design decisions, and a unit built for a 400 Hz ground supply is not automatically able to deliver a 60 Hz test bench. Tell us every frequency and voltage the installation has to serve and we will tell you whether it is one machine or two.
06What documentation is expected on defence supply?
More than on commercial work, and it should be agreed before manufacture rather than after. Test certificates, inspection stages, traceability of major components and any customer or third-party witness of testing are commonly specified, and each affects the build programme. Send the technical specification and the quality requirements together at enquiry so the inspection plan is priced and scheduled into the job.
We will do the load grading with you
Site survey, load list and a single-line diagram before anything is quoted. That is where the specification is actually decided.