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As electricity cannot be seen,

smelled or heard (when all is

well), it is a technology that can

be more difficult to grasp than,

say, mechanical engineering or

architecture. Nevertheless, over

the past century we have come

to increasingly rely on electrical

energy. It only takes a power cut

for us to all realise how much we

depend on electricity for our luxury,

safety and comfort.

The luxury, safety and comfort we take

for granted at home and at work is also

appreciated onboard a yacht or in a

camper. The same goes when working

in locations with no connection to a

power plant, including on tugboats, Rhine

barges or during road works.

For more than 20 years, Mastervolt

has specialised in supplying reliable

electrical power in places without utility

facilities. To offer a better understanding

of our products, let us first give a short

explanation of the main terms.

Voltage and current

provide power

The main activity of Mastervolt is power

conversion. And the main variable that

can be converted in the field of electricity

is voltage. The electrical voltage is the

potential difference between two points

in an electrical circuit.

We distinguish two types of voltage:

Alternating Current (AC) and Direct

Current (DC). Voltage is expressed in

volt (V), and AC frequency is expressed

as hertz (Hz), the rate at which voltage



Alternating Current

(voltage) is the

electricity that comes out of home

sockets and is used for most appliances.

In Europe this is 230 V 50 Hz, in the USA

120 V or 240 V 60 Hz.


Direct Current

is supplied by a battery

or solar panels. Batteries are vital

because they offer a practical possibility

to store electrical energy. Battery voltages

are commonly 12 V or 24 V. Another

possibility is 48 V, which is usually

exclusive to electric propulsion.

While direct current is stored in batteries,

we actually need alternating current to

power our household appliances. This

requires conversion from DC voltage to

AC voltage.

Another term we use is


current (I)


measured in


amps (A)


Current ‘flows’ through the onboard

wiring when there are electric appliances

in use. The amount of current that

flows through the wiring can vary

greatly (depending on the connected

load and used voltage). This is why the

correct cable thickness is so important

– overheating electric wires can have

serious consequences.

A running river, a wire that conducts

electrical current, or a cyclist biking

against the wind… All experience


In the field of electricity, this




is indicated in


ohm (Ω)


Resistance is important because it causes

losses in the form of heat, and we need

to take this into account. Voltage loss

takes place in wires and, if it is not dealt

with, there will be insufficient voltage

at the end of the wire to power the

appliance we want to use.

The mentioned variables all provide


power (P),

which is expressed in


watt (W).

Every electric device refers to

its output in watt; microwaves of 900 W,

light bulbs of 60 W, generators of 4000 W

and washing machines of 2500 W.

To keep the terminology and discussion

simple, we refer to kilowatts (kW), in

which 1000 W equals 1 kW. To link

consumption to a consumption period,

we use a time unit in which electrical

power is generated or consumed, namely

one hour. Together they make kilowatt

hours (kWh).

Electricity: How does it work?

The relationship between these units is expressed in formulas

that represent the ‘laws’ of electricity.


= potential difference expressed in voltage (V)


= current in units of amps (A)


= resistance in units of ohm (Ω)


= power in units of watt (W)

Ohm’s Law is the most important formula. V = I x R

Voltage [V] = current [I] x resistance [R]

Because we often use the term power, the formula below is

frequently used to determine power: P = V x I

Power [P] = voltage [V] x current [I]