The drive motor


Types of drive

• Petrol engines should be considered when the power generator should be compact for mobile use and when only running for average periods for variable operation is expected.
• Diesel engines are heavier and more sturdy and therefore better suited for longer running times. The specific fuel consumption of diesel engines is lower.

Starting system

There are two basic types of starting systems:
• Recoil starter to crank the engine manually as opposed to an automatic wind-up rope.
• Electrical starting over an ignition switch (a prerequisite being that the battery is present)


When high speed and when low speed?


High speed:

• 3000 rpm petrol or diesel engines
• Engines for daily use: for about 4 - 10 hours
• Life = service time: about 3,000 - 5,000 hours
• Applications: Building sites, skilled trades, road construction.u

Slow runners:

• 1500 rpm diesel engines
• Engines for constant operation: 24 hours
• Life = service time: 10,000 - 20,000 hours
• Applications: Current and emergency power supply

  Synchronous Asynchronous
Application All ohmic and inductive consumers Only ohmic consumers without any restrictions. Inductive consumer with considerable restrictions.
Starting behaviour Trouble-free starting, regardless of the consumer. Compound-regulated generators with three times the starting current. DUPLEX generators with four times the starting current Problematic starting with the most difficult to start consumers - especially for generators without start amplification. For generators with start amplification, larger generator dimensions are needed.
Load capacity The generator can handle a 100% load even with inductive consumers and it can therefore have a smaller design. With inductive consumers, the generator can only be loaded up to 1/3 (without start amplification) and 2/3 (with start amplification).
Regulation Mechanical regulation IP 23,Electronic regulation IP 54 Usually unregulated, condenser
Protection Class Design-dependent internal cooling IP 23,Design-dependent external cooling IP 54 Design-dependent IP 54, external cooling.
Protective measures Safety-separated circuit as personal protection An FI circuit breaker is not necessary Safety-separated circuit as personal protection - A circuit breaker is not needed
Asynchronous 230 / 400V generator with condenser controlling for appliances with a low starting current, cannot be overloaded
Synchronous 230V generator with condenser controlling for consumers with starting current, not suitable for electronic consumers
Synchronous 230V generator with AVR controlling (1) a stable output voltage for simple electronic consumers as well as for appliances with a low starting current, not suitable for electronic consumers with a very high starting current
Synchronous 400V generator with compound controlling (2) consumers with a very high starting current, not suitable for electronic consumers, never suitable for an asymmetric load (3)
Synchronous 230V generator with inverter controlling universally usable, a precise output voltage and frequency for sensitive consumers, as well as consumers with a starting current
DUPLEX 230 / 400V generator with electronic controlling universally usable / suitable for an asymmetric load (3), a precise output voltage and frequency for sensitive consumers as well as consumers with a high starting current (4)

(1) AVR - Automatic Voltage Regulation
(2) Control of the generators voltage takes place through an additional magnetic field (a compound transformer is installed in the stator)
(3) An asymmetric load is understood as non-uniform loading of a three-phase generator.
(4) The smaller the distortion factor the cleaner the supply voltage


12V DC which can be used for charging batteries
230V AC the most frequently used type of current. Nearly all electric tools, lights and garden and construction machines can be run on it
400V three-phase used at home for appliances like washing machines or cookers, and on construction sites for powerful consumers suxh as cranes or circular construction / table saws
V volts Voltage (12 / 230 / 400)
Hz Hertz Frequency (50 / 60)
A Amperes Current strength
W Watts (x 1000 = kW) Active power (2)
VA Volts Amperes (x 1000 = kW) Apparent power (1)
Cos ϕ Nominal established output factor Power factor (0.8-1)

(1) Apparent power (3) - data in VA or kVA - is the power the generator can generate
(2) Active power (3) - data in W or kW - is the power that can be drawn from the generator, depending on the generator’s power factor.
(3) Reactive power - the difference between active and apparent power. This is important for covering the starting current.

Electrical safety


All mobile generators are designed as standard in the protection measure with a circuit breaker with potential equalization. They fulfil the requirements according to DIN EN 12601. No earthing is necessary for this protection measure.


The FI protection switch (RCD)

The FI circuit breaker provides further protection against dangerous currents. It shuts off the power supply if there is fault current. This protection measure requires appropriate earthing in which the earthing spike is connected to the generator’s earthing screw for potential equalisation by an earthing cable. This is how a potential equalization is created.


Safety-separated circuit - insulation monitoring with shut-off.

The appliances turn themselves off automatically if the insulation resistance reaches a critical level. The insulation monitoring function is controlled from a test button. Costly earthing with an earthing spike and earthing cable are no longer necessary. This equipment provides a high level of safety, especially in underground construction such as work on gas and water mains (moist environments). It is even obligatory for pipeline construction according to DVGW GW 308.

IP = International Protection according to DIN 40050

The IP code consists of two digits that indicate the specific degree of protection. The first digit indicates the protection class for touch and foreign object protection, and the second indicates water and moisture protection.

- O Unprotected
- 1 Dripping water, vertical
- 2 Dripping water, diagonal to 15° from the vertical
- 3 Spray water diagonally up to 60° of the vertical
- 4 Splashed water, from all directions
- 5 Water jet, from all directions
O - Unprotected
1 - Foreign objects > 50 mm
2 - Foreign objects > 12 mm
3 - Foreign objects > 2.5 mm
4 - Foreign objects > 1.0 mm
5 - Dust protected


Appliances in a nutshell


Ohmic appliances (active load appliances)

These are consumers that convert their power input completely into heat or light and therefore they do not present problems for any generator. The listed output power (watts) is always also the input power that is taken from the generator. Such appliances include heating devices and hot plates.

Inductive consumers

These are appliances that are driven by an electric motor. With these inductive devices, friction losses and winding losses result in only about 70% of the input power being available as output power. Additionally, when the motor is turned on, more power is needed. Depending on the type of device and the motor’s quality, this can be 3 to 6 times the input power. Such appliances include compressors, table saws and high-pressure cleaners.

Capacitive appliances

These include critical consumers that, due to their charging function, can be powered safely by specially equipped DUPLEX or synchronous generators. They include flashers or discharge lamps.