ALFA IN - development, production, sale and service of Professional Power Generators MEDVED

How to correctly choose MEDVEDA (power generator)


What you need to know for the right choice of power plant.


1. 1 x230V, 3 x 400V or cardan

You need to answer the question of what you will primarily use the generator for, whether it is sufficient

  • single-phase power plant 1x230V,
  • or it will occasionally be necessary to power three-phase appliances 3x400V
  • or the primary job is to weld.

But there’s one more question you can’t ask most of the competition. Do I need it with a motor? Do you need to have an engine or tractor in your fleet that is equipped with a cardan output? If so, M-Watt is the clear choice!

2. What regulation will you need?

If you want to choose the output of the power generator correctly, we need to know quite precisely the input power of your appliance and the type of appliance, especially in terms of requirements for supply voltage fluctuations and the load characteristic of the load changes of the power generator (current peaks during start-up or step changes in input power during operation).

2.1. AVR regulation (Automatic Voltage Regulation)

If, it is an appliance, that you know is sensitive to voltage fluctuations (e.g. computer, sensitive medical devices, tools with electronic control of input voltage), you need to choose carefully the type of power generator output voltage regulation. You will use a power generator with the AVR. It is an electronic regulation of the output voltage, which ensures that the fluctuation of the output voltage will be within a tolerance of ± 2% in the entire range (at constant load) up to the nominal power of the generator. (AVR is not needed for PEGAS or ALFIN welding machines with PFC – power factor correction, which are not susceptible to voltage fluctuations, but it is necessary to count on a power reserve of power plants of at least 30%).

2.2. Compound CCL regulation (Compound Controlof Load)

If, you need to “spin” an asynchronous motor of a circular saw, a ceramic tiles cutter, or air compressor, i.e., a device with a high peak start-up, then you definitely choose a power generator with a compound transformer. These motors really have a “HARD START”, but the compound transformer ensures that the power generator is able to cover a large starting peak current, even in case of the voltage drop. A lower voltage has no influence to the asynchronous motor in any way. You should calculate, that for your “1 kilowatt” motor you need 2 – 4 times of motor nominal power for the short time period. PEGAS or ALFIN inverter welding machines with PFC (Power Factor Correction) – can be supplied without any problem by power generator with a CCL regulation.

2.3. CCL capacity regulation

The last group of appliances are hand electric tools with commutator motors, for which the output voltage capacitive regulation is sufficient. The power consumption of the supplied appliance can be same like the maximum value of the power generator nominal power output.

3. Possibilities of protection against dangerous contact with hazardous live parts

3.1. Standard

The safety of the device from the point of the possibility of electric shock is ensured by separated winding of the alternator from the connection to the ground (no earthing).

3.2. Optional accessories (electrical switchboard, safety switches, current circuit breaker)

The current circuit breaker (CCB) ensures safe operation and protects the operator in the event of insulation damage. The CCB disconnects the electrical circuit in the event of electrical current difference between the power output of the alternator and the part of the circuit connected to ground behind the CCB output.

!!! It is strictly prohibited to connect PE conductor and N conductor to PEN joint connection !!!

4. Selection according to performance and type of power supplied device

The coefficient determines the approximate multiple increase of the “label” nominal power consumption of powered devices, which may occur for a short time period, especially during the start-up of the device. Most devices have a coefficient of 1, with the exception of those is listed below (the list is not complete, it is only an example).

3Pressure washers
 3.5 – 5Refrigerator
2.5Concrete mixers, manual angle grinders, circular saws
2Machine tools and electric grinders
3Submersible pumps
4Washing machines
3,5 – 5
1.5Drilling and milling machines, halogen and luminescent lights
2Shredders, string trimmers, brush cutters, hedge trimmers, mowers and chain saws
The coefficient by which it is necessary to recalculate the required power of the power plant

We will be happy to help you with choosing of new a power generator. Alternatively, we can come to test to supply the selected devices, because in some cases is difficult to determine power supply by calculation. These devices are mainly compressors, groups with multiple powered devices, servers with UPS, cooling boxes, etc. These devices have mostly voltage 400V and power output from 9-10 kVA and higher. In these cases, customer will agree date of testing by expert with business manager of the manufacturer ALFA IN a.s. or external sales representative. The expert will arrive at the agreed date directly to the customer with several types of generators and will performs a real test. For realization of this test is necessary to provide customer own worker responsible for connecting the resources. This worker must have the appropriate authorization to enter the customer’s electrical network. The manufacturer will provide power generators and an expert to operate them for testing. The manufacturer’s expert has no rights to connect or make changes of the electrical installation of the customer. In the Czech Republic and Slovakia, we are able to realize these performance tests approximately 1-2 weeks after the first contact.

The manufacturer ALFA IN a.s. realizes these tests to the customer free of charge without obligation of future purchase, but with fulfilling of customer cooperation mentioned in the text above.