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Semidan Power

Uninterruptible Power Supplies (UPS), Chargers, Inverters and Ground Power Units (GPU)

Allingebjergvej 3,
DK-4050 Skibby,
Fax Number

Semidan develops standard and special UPS systems, chargers, inverters, frequency and DC/DC converters and ground power units (GPU). We are a 100% Danish-owned engineering company, established in 1978.

Uninterruptible power supply systems (UPS)

Semidan Power designs and manufactures UPS systems from 200VA – 4.8MVA.

All Semidan systems are controlled by an advanced power transistor technology PWM inverter with high-frequency switching, which also ensures very low acoustic noise, low weight and small dimensions.

Semidan UPS system construction

A modern UPS system consists of charger, battery, static inverter and static switch. A Semidan UPS system is often constructed in such a way that a completely uninterruptible supply is achieved.

Semidan Power is a Danish engineering company that manufactures uninterruptible power supplies (UPS), chargers, inverters and ground power units (GPU).<br/><br/><br/><br/><br/><br/><br/><br/><br/><br/>
The 28V GPU is very user friendly - it can be single-handedly operated by one person.<br/><br/><br/><br/><br/><br/><br/><br/><br/><br/>
The 400Hz GPU is a static frequency converter (SFC) available in 20kVA, 40kVA, 60kVA, 90kVA, 120kVA, 150kVA and 180kVA versions; it can be either mobile or stationary and is suitable for both indoor and outdoor use. <br/><br/><br/><br/><br/><br/><br/><br/><br/><br/>
Stationary and bridge-mounted anti-rust GPUs for indoor and outdoor applications.<br/><br/><br/><br/><br/><br/><br/><br/><br/><br/>

In normal operation the charge condition of the battery is maintained by the charger. At the same time the charger supplies the inverter with DC voltage. Within the inverter the DC voltage is converted into a sinusoidal alternating voltage completely independent of the incoming mains and therefore always stable with regard to voltage and frequency.

In the event of mains failure the inverter will still supply the load, but now from the energy stored in the battery. The supply of the connected load will therefore be completely independent of mains failure(s).


The charger in a static no-break system can be a thyristor or switch mode-regulated charger with galvanic isolation. It can be a one or three-phase system depending on consumer specifications or the size of the load. The charger is in each case adapted to the batteries and is equipped with high, discharge and low DC alarms as standard.

The charger can also be equipped with a monitoring system that will monitor the charging voltage and test the capacity of the batteries at intervals decided by the user. Alarms can be visual and/or controlled remotely by switches.

Semidan Power produces chargers with all input voltages depending on customer application, for example:

  • 3 × 115V, 400Hz – 3 × 230V, 60Hz – 3 × 400V, 50Hz
  • Output voltages: 24V, 36V, 48V, 60V, 110V, 220V and 400V (or as requested)
  • Output currents: 10A to 2,500A (or as requested)

The chargers can also be constructed with voltage and/or current controlling for applications such as anti-fouling systems, multi-battery systems and airplane engine testing.


Semidan inverters are manufactured up to 4MVA and are controlled by PWM technology.

As input, any source of DC can be used, as long as it is within the specifications of the inverter, typically from +24V to +400V, +20% / -15%.

The output voltage will be ±1% and the frequency will be ±0.5%, independent of input voltage and load.

Ground power units

Sold to various airports around the world. There are two main versions of GPU produced by Semidan: 28V and 400Hz.

28V ground power unit

The mobile or stationary, semiconductor-controlled 28V GPU is available in 300A and 600A versions or to customer specifications upon request. It is highly efficient and is suitable for use both indoors and out. It has and overload of 500% (1,500A/sec or 3,000A/sec).

The 28V GPU is user friendly – it can be single-handedly operated by one person, has no sharp edges and is easily towable. The GPU is made of a glass fibre canopy meaning that the unit will not rust or corrode. The canopy may also be provided in a choice of colours.

The GPU cable is easily stored and the unit has very quiet operation.

400HZ ground power unit

The 400Hz GPU is a static frequency converter (SFC) available in 20kVA, 40kVA, 60kVA, 90kVA, 120kVA, 150kVA and 180kVA versions. It can be either mobile or stationary and is suitable for both indoor and outdoor use.

The GPU can operate in parallel and has 250% load/sec. At full load the efficiency is greater than 93%. The unit also has a logical fault diagnosis system.

The 400Hz GPU has similar additional features to the 28V ground power unit making it very user friendly.

Semidan Power ApS

Allingebjergvej 3
DK-4050 Skibby

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