Inverter INV-120V-40A · GaN
GaN inverter INV-120V-40A – 99 % efficiency for 90 days in the stratosphere
Six gallium nitride half-bridges arranged as three full bridges for a motor with open windings: up to 120 V, 40 A phase current (rms), 99.125 % efficiency. Developed for a HAPS platform that stays airborne for 90 days at a time – and optimized for efficiency without compromise.
99.125 %
inverter efficiency
120 V · 40 A
DC-link voltage · phase current (rms)
6 × GaN
half-bridges, arranged as three full bridges
90 days
flight duration of the platform, no maintenance
Application
For 90 days of flight, every watt counts.
HAPS – high-altitude platform stations – are solar-electric aircraft that circle for months at an altitude of around 20 kilometers and perform tasks that would otherwise require a satellite. By day the sun charges the battery, by night the battery carries the flight. The energy budget decides everything: every watt of loss in the drive means more solar area or more battery mass – and both add to the mass the aircraft has to carry.
Then there is the thermal side: in the thin air of the stratosphere, convection hardly cools. Heat generated in the inverter has to be dissipated through surface area and thermal mass – so the most efficient cooling is not to generate the losses in the first place. And 90 days without maintenance demand a design with margin: conservative currents, low junction temperatures, no component at its limit.
The design goals
- Maximum efficiency at the operating point of sustained flight – not only at full load
- Minimum heat loss, because convection barely cools at 20 km altitude
- Continuous operation over 90 days without maintenance, with margin in every component
- Low mass: inverter and motor optimized together
The result: an efficiency of 99.125 %.
Topology
Three full bridges instead of one three-phase bridge.
A classic three-phase inverter consists of three half-bridges; the motor is connected in star or delta, and each phase sees at most the voltage between two bridge legs. The INV-120V-40A takes a different route: its six GaN half-bridges form three full bridges, and each motor phase is connected as a separate winding with two terminals to its own H-bridge – a motor with open windings (open-end winding).
This has three consequences. Each phase can use the full DC-link voltage – for the same power the motor is wound for higher voltage and lower current, and the conduction losses in transistors, cables and winding fall with the square of the current. The three phase currents are controlled independently of each other; the field-oriented control sets Id and Iq and keeps the zero-sequence current at zero. And the phases are electrically decoupled from each other – the basis for fault-tolerant operating modes.
The matching motor also comes from Persystems: winding, pole count and inverter are designed together for the operating point of the platform.
Three full bridges, six half-bridges
Each phase on its own H-bridge – the full DC-link voltage per winding
GaN half-bridge (upper and lower switch) motor winding with two terminals
Schematic. The control sets the three phase currents independently and keeps the zero-sequence current at zero.
Semiconductors
Why gallium nitride.
Switching almost without loss
GaN transistors switch in nanoseconds and have no reverse-recovery charge. Switching losses are a fraction of those of silicon MOSFETs – at the same or a higher switching frequency, which keeps the current ripple in the motor small.
Low conduction losses
Six half-bridges with low on-resistance, operated far below their limits: the chip temperature stays low, and with it the on-resistance.
Less heat, less mass
What is not dissipated as loss does not need cooling: smaller cooling area, less weight – on a platform where every gram costs solar area and battery, the decisive lever.
Technical data
INV-120V-40A at a glance.
| DC-link voltage | up to 120 V |
| Phase current | 40 A rms (maximum) |
| Power stage | 6 GaN half-bridges, arranged as 3 full bridges |
| Motor connection | 3 phases with open windings (6 leads) |
| Efficiency | 99.125 % |
| Control | field-oriented (FOC), independent phase current control |
| Design focus | maximum efficiency, 90-day continuous operation |
| Application | HAPS and long-endurance flight; drives with the highest efficiency demands |
| Motor | matching motor with open windings, developed by Persystems |
| Availability | available |
| Datasheet | on request |
Scope of delivery and integration
What you get
- Inverter INV-120V-40A and matching motor as a tuned drive unit – or the inverter for your motor with open windings
- Adaptation to your platform: voltage, current, interfaces, form factor
- Efficiency map from our own test bench – power analyzer, torque transducer, CAN logging
- Support from our engineering team for design and system integration
Field-oriented control, telemetry and protection functions come from the same firmware base as in the INV-60V-120A.
FAQ
Questions about the INV-120V-40A
Why a full-bridge inverter and not a classic three-phase inverter?
Because with open windings each phase can use the full DC-link voltage. The motor is wound for higher voltage and lower current, and the conduction losses in transistors, cables and winding fall with the square of the current. For a platform where every watt of loss costs solar area and battery mass, that is the most direct lever.
What are the advantages of GaN over silicon MOSFETs?
Gallium nitride transistors switch in nanoseconds and have no reverse-recovery charge – switching losses are a fraction of those of silicon. Together with low conduction losses this yields the efficiency of 99.125 %, and less heat loss means less cooling area and less mass.
Can I use the INV-120V-40A for my project?
Yes. The inverter came about for a HAPS platform, but the design suits any drive where efficiency and mass are decisive: long-endurance flight, solar-electric vehicles, test benches with efficiency requirements. Tell us voltage, current and operating point – we check whether the standard variant fits or an adaptation is needed.
Is there a matching motor?
Yes. For the HAPS platform we developed the motor with open windings together with the inverter. You get inverter and motor as a tuned unit – or the inverter alone for a motor whose six winding ends are brought out.
What does 40 A phase current rms mean?
The maximum rms value of the sinusoidal phase current the inverter can deliver – the figure from which, together with the motor constant, the torque follows. The peak value is higher by a factor of √2, at around 57 A.
Contact
A drive where every watt counts?
Tell us voltage, current and operating point of your drive – you get an answer straight from engineering.
| Product | GaN inverter INV-120V-40A |
| Key data | up to 120 V, 40 A rms, 99.125 % efficiency |
| Sales | sales@persystems.org |
| Phone | +49 941 462 974 40 |
| Company | Persystems GmbH, Regensburg, Germany |