White - blue - orange, Herbert's Railway-Site

MÄRKLIN H0 conventional driving and electromechanical automatisation

A4: White – blue – orange –
transformers between fine and evil

ATTENTION: Safety-relevant topic!!!

The topic of the old Märklin transformers is a recurring one.

The conclusion up front:

The white Märklin transformers no. 6647, 66470, 66471 are recommended in the area of power supply with 230V.

But other mothers have beautyful daughters too…

First, let’s take a look at the Märklin transformers since 1949.

Only transformers for 220V or 230V and for the German market are listed.

A click on a transformer image shows the catalog sheet of the respective year.

10VA

16VA

30VA

blue sheet metal housing

1949
to
1951

At that time, the round plug, as shown in the pictures, was the „normal appliance plug“.

1952

(15VA)

1953
to
1956

From 1957 onwards, all Märklin products were given new numbers with unchanged design.

In the 1950s, the SCHUKO system gradually replaced the previous normal round plugs and flat sockets in Germany. Because the mains cable has to be firmly attached to the toy transformer, the variants on offer now doubled.

1957
to
1959

1960
to
1961

From 1960 the contour plug with the shape of a SCHUKO plug became standard in Germany, still 2-pole without protective earth, and the old “normal appliance plug” remained in the catalog “for special cases”.

Märklin assured in the catalog: “This transformer complies with the lastest official regulations.” or “…latest regulations of the VDE”, from 1961 on: “The transformer … has been tested and approved by the VDE.”

1962
to
1964

1965
to
1967

1968
to
1972

From 1968 onwards, the mains cables were fitted with the “unified plug”, toda called the EURO plug.

The two Primex transformers also date from this time.

identical in construction 6413

identical in construction6117

blue plastic housing, EURO plug

1973
to
1974

still sheet metal housing

1975
to 1991

In 1975, the sheet metal transformer 6511 was still listed in the German catalog without picture.

From 1992 onwards, the plastic transformers were fitted with safety terminals instead of sockets at the output.

1992
to
1993

white plastic housing

32VA

1994
to
1995

Only with the Alpha programm

1996
until
2010

Numbers become 5 digits.

2011
until
2015

A power switch is added.

2016
until
today

Now we examine why oder transformers should be used with caution or better not.

The problems with the older transformers are:

1^st: the current electrical regulations

2^nd: the ageing of the insulating materials in the transformer and the connection cable

3^rd: the increase of the mains voltage from 220V ±22V to 230V ±23V since 1987/2009 (see Wikipedia)

To 1st: The applicable electrical regulations

Some applicable regulations contradict the operation of the old sheet metal transformers. Unacceptable insulating materials, even if they were new, construction features of the components.

The transformers up to 1959 in the table lack protective insulation. Please do not use them any more! I disposed of mine.

The protective insulation can be recognised by the symbol on the type plate: a square within a square. The transformers from 1960 onwards therefore have protective insulation.

All transformers with a double square in the type plate should be safe, but you can only be completely sure if you have the transformer checked by a recognised specialist company, especially for the condition of the protective insulation.

Make sure that the supply cable is intact and free of cracks or brittle changes.

The transformers are not suitable or approved for damp rooms.

This means that some basements are unsuitable for operation.

For further, more in-depth explanation, I bring here the report of a member of my Facebook group, the master electrician Dieter Hammerl:

The tale of the blue metal transformer with the red rotary knob, which is dangerous.

To put an end to this discussion, I took the liberty of scrapping one of my transformers today.

Since it is now open, it has lost its operating licence.

I am a master electrician and could close this transformer again so that it could be used, but I won't do it; who knows what else it is good for.

The first picture shows which kind of transformer it is.

The second picture shows the connection side with the symbols.

On the third and fourth picture you can see the transformer assembly.

The fifth picture shows the arrangement of the coils / windings and the galvanic isolation of the coils from each other and from the transformer core.

The sixth picture shows the protective insulation that prevents an active conductor (wire) from touching the housing.

In the case of the transformer shown, mechanical precautions have been taken to ensure that no conductive connection can occur between an active conductor (230V) and the housing. However, this also presupposes that the transformer is still in the original condition in which it was delivered from the factory. As soon as the transformer shows deformations or changes in colour or massive rusting or the connection cable is porous and the insulation is possibly already crumbling or partially missing, the transformer has lost its operating licence and must be disposed of. The transformer should also be disposed of if the connection cable has been replaced and there is no new safety certificate on the transformer issued by a specialist electrical company.

The statements only refer to the electrical operational safety.

I cannot rule out the possibility that this transformer will fry decoders or send electronic components to nirvana heaven with its switching voltage, as I only drive conventionally.

The last picture also shows a blue transformer, but with a plastic housing.

I advise against using even older transformers, as they have reached their end of life.

In general, if you don't have a good feeling about using the transformer described or another transformer with a metal housing because you don't know whether it has been operated in accordance with the regulations, dispose of the transformer.

End of quote

To 2nd: The ageing of the insulating materials in the transformer and the connecting cable.

Many a person has had an old cable crumble in their hands. Replacing the supply cable requires opening the riveted housing, which can lead to uncontrollable new damage inside. The effort and the new risk are not worth it.

The old blue Märklin transformers with sheet metal housings are many decades old and meanwhile "End of Life", are no longer considered safe to operate.

And another quote from Dieter Hammerl:

For all those who think that transformers with a blue housing and a red regulator could lead to a fatal electric shock.

As I have written in other posts, these transformers are "protective insulated" and produce a "protective extra-low voltage" suitable for toys.

"Protective insulated" means that no active wire or active component (230 V) can touch the metal housing.

"Protective extra-low voltage" means that the windings (coils) are galvanically separated and also cannot touch the transformer core. It also means that no "autotransformer" may be used.

By BillC - Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=524847

What is an "autotransformer"? (see Wikipedia)

(Graphic by BillC - Own work, CC BY-SA 3.0)

This type of winding is often used for household appliances, in consumer electronics and everywhere where you want to save money. With an autotransformer, only one winding is wound and, for example, the winding for 12 V has a tap on the outside. In this case, the primary and secondary windings are not separated and, in the event of a winding short, i.e. the often-mentioned crumbling insulation of the winding wires, or a winding break, 230 V could suddenly be present on the 12 V side.

Autotransformers must not be used for toys!

But if you want to do something extra for your safety, you can have the circuit to which the transformers are connected by means of a Europlug (the flat plug without a protective contact) equipped with its own residual-current device (RCD). This is a change to the sub-distribution and must be carried out by a recognised electrical specialist, i.e. your favourite electrical installation company.

What does this residual-current device (RCD) do?

If, contrary to expectations, the connection between an active component and the housing, which is often invoked, should occur, you will receive an electric shock from the transformer when touching the housing. However, this is not dangerous because the residual current circuit breaker ensures that a maximum voltage of less than 50 V can build up across the resistor, i.e. the connection between you and the transformer housing and your contact with the ground. And 50 V is not dangerous for you.

If it is not possible for you to have an additional residual-current device (RCD) installed in the distribution board, ask your trusted electrical installation company to build you a small distribution board from an insulated housing. He will provide the supply line with a protective contact plug, which you can then plug into your socket and at the other end he will build a socket strip with 10 or more sockets.

Please do not plug any other multiple sockets into the sockets here, otherwise you will lose your insurance cover. According to the recognised rules of technology and the rules of property insurers, it is not permitted to plug other multiple sockets into a multiple socket.

So: Not like that... (Photo: Herbert Otto, Father's workroom)

And in all confidence, which modeltrain specialist has not plugged at least one multiple socket into a multiple socket? I would be much more concerned about this than about whether an ACTIVE COMPONENT can touch the housing of a device with protective insulation.

The basis of this consideration is always the fact that the Märklin transformers used are still in their original condition and the cable or housing does not yet have any damage. Damages are among others:

porous cable insulation,
moisture damage,
damaged housing or housing opened by a non-expert,
damaged or altered cables,

etc.

End of quote

To 3rd: The increase of the mains voltage from 220V ±22V to 230V ±23V since 1987/2009 (see Wikipedia)

I would like to add some basic knowledge to Dieter's comments:

What is "the mains voltage":

230 volts AC with 50 hertz frequency.
This is what comes out of the sockets of the household electricity grid in Germany and many other countries.

Where does this apply?

This was not always the case:

Before 1987, when transformers were manufactured for 220 volts, the mains voltage was allowed to be between 198 and 242 volts (220±22V) and that is what the transformers were built for.

In a transitional period between 1987 and 2009, the mains voltage was allowed to be between 207 and 243.8 volts. However, the manufacturers knew which rule would come after that and built their devices for the voltage range 207 to 253 volts (230±23V), which still applies today.

The actual mains voltage varies regionally and also depends on the large consumers in the area. Where I live in the northern outskirts of Berlin, I regularly have between 221 and 229V, mostly 223V.

Physical principles of the transformer

1st fact:

A current-carrying conductor causes a magnetic field in its surroundings (discovery by Hans Christian Ørsted in 1820). (Wikipedia)

If you take several insulated wires in parallel and send current through them in the same direction, you get a stronger magnetic field, the individual magnetic fields add up.

If you wrap the insulated wire around an iron core, you build an electromagnet. (This only works with iron materials, with a few exceptions. Problem: iron can rust...)

An electromagnet works with both direct current and alternating current.

With direct current, the iron core tends to become permanently magnetic itself. This does not happen with alternating current.

2nd Fact:

When you move a wire through a magnetic field, the magnetic field in the wire creates an electric voltage.

(Demonstrated: induction on the conductor swing).

Mind you, there has to be movement:
either you move the wire (generator, dynamo),
or you alter the magnetic field.

If you feed an electromagnet with alternating current, the magnetic field constantly builds up and degrades. It's like moving the wire. So the wire may be stationary and yet a voltage is generated in it.

Now we know how to make a magnetic field electrically and how to generate electricity with a magnet:

You expose a second coil to the magnetic field of an electromagnet fed with alternating current, preferably by winding both coils on a common iron core.

Image by BillC at the English-language Wikipedia, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=27407689

The number of turns of the two coils determines how the electrical voltage is transmitted:

For example, if the number of turns of the two coils is in a ratio of 1:10, i.e. one coil has 100 turns and the other has 1000 turns, then the ratio of the voltage going in to the voltage coming out is also 1:10. So 230V in and 23V out.

In the Märklin transformer there are such two coils on a common iron core, optimised for the purpose of model railway supply.

The wires are insulated with only very thin varnish.

The number of windings is chosen in such a way that 230V at the input results in 4V (in the case of the Märklin transformer 6647, 66470, 66471) at the output.

Why only 4V?

As mentioned, the insulating lacquer around the wires is only very thin. It is removed at certain points so that the pick-up finger of the controller knob can touch the bare wires.

When the pick-up finger touches the first wire, it picks up the said 4V there. The wire next to it, one turn of the coil further, has a very slightly higher voltage. From wire to wire, the voltage increases until it reaches 16V at the last wire. This is how the regulation works.

For the 25V switching voltage, there are more turns, but they are not reached by the pick-up finger, but are tapped directly and are available to the left of the 0-point.

Once this is understood, it is clear that a transformer built for 220V delivers somewhat higher output voltages at 230V mains voltage. In addition, there are manufacturing tolerances that sometimes lead to values that cannot be fully explained.

If you then add the changed permissible tolerances, some old transformers can produce unpleasantly high voltages at the limits of the permissible mains voltage. Unpleasant above all for electronic components...

If you operate a digitalised traction unit in conventional mode and use a transformer that generates too high a switching voltage, the electronics can be destroyed. The critical limit is probably a good 30V; exact details are nowhere to be found.

The ratio of input voltage to output voltage is invariably determined by the number of winding turns.

A transformer that was built for 220V ±22V and brought a switching voltage of 21.6V to 26.4V can today bring up to 27.6V.

That is the theory and does not sound particularly dangerous.

A modern transformer for 230±23V has coils adapted to the voltage difference from 220V to 230V. Therefore it should also deliver 21.6V to 26.4V.

Now I have measured my most modern Märklin transformer no. 6647.

And lo and behold, at 253V input it delivers max. 27.9V at the output.

It should have delivered 26.4V, which is 1.5V more.

So far, no traction unit has been damaged by this transformer.

Therefore, I assume that approx. 28V is still harmless.

However, I have at least one member in the group who has had decoders break down with a white transformer.

I have measured all my transformers.

The following ranking list refers to the reversing switch voltage at 230V mains.

rank

brand

housing

power

for V

reverse voltage at 230V mains

Märklin

6647

plastic

32VA

230V

25,2V

Titan)*

808M

sheet metal

60VA

220V

25,5V

Märklin

6631

plastic

30VA

230V

26,2V

Titan)*

109M at
108 Universal )*

sheet metal / plastic)*

60VA

220V

26,4V

Märklin

6173

sheet metal

30VA

220V

27,2V

Märklin

6631

plastic

30VA

220V

27,5V

Märklin

6413

sheet metal

10VA

220V

28,8V

Märklin

6511

sheet metal

16VA

220V

29,0V

Primex

6401

sheet metal

10VA

220V

29,1V

Märklin

37540

plastic

10VA

220V

30,1V

)* The Titan system transformers each consist of a mother transformer and plug-in controller units.
The 808M is a sheet metal tansformer with controller, to which additional 809M sheet metal controllers can be connected at a 8-pole socket field on the side.
The 108 Universal is only available as a transformer with a 5-pole plug-in connector on the side, with a sheet metal or plastic housing, to which the platic 109M controllers can be connected.
I go into this systemim more detail in the article “How many transformers do I need- and which ones?”.

The worst is Märklin No. 37540 with over 30V, at 253V mains up to 33V.

Actually a modern transformer with plastic housing.

So the plastic housing is not a sign of safe use!

I would not operate a digital locomotive with this one, at most permanently set for a track without switching.

That's the recommendation for people who can't throw anything away.

Märklin writes about this (German):

https://www.maerklin.de/fileadmin/media/service/faq/Technik-Tipp-207.pdf

Light transformers

1965
to
1967

6210
sheet metal housing
220V
50VA
SCHUKO plug

1968
to
1972

6211
sheet metal housing
220V
50VA
EURO plug

1973

6611
plasic housing
220V
40VA

1974
to
1991

6611
plasic housing
220V
40VA

1992
to
2004

6002
230V
52VA

2005
to
2010

60052
230V
60VA

I own only one 6611 in the design from 1974.
Instead of the written 16V it delivers
at 220V mains 18,6V (that was already too much at the time of production),
at 230V mains 19,5V.

Furthermore I own a light transformer from Piko, No. Z1 1756, giving
at 230V mains 19,6V

and a light transformer from Roco, No. 10725, giving
at 230V mains 15,7V.

The Prototype Märklin-H0-Knowledge Layout-Building Modelstock

state: 07.01.2024 15:13

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