How do we make... contact

Posted on April 07, 2015 by Yvonne Wirth, Images by Robert Hack

The wiring is the nerve and motor control system of a genset. The mtu electricians have to connect up as many as 800 such colored cores on every genset.
Friedrichshafen, Germany

A gentle humming and then the powerful Series 4000 mtu gensets start up. They provide the emergency power supply for whole urban districts or hospitals, for example. Or even the onboard power on a luxury yacht. But for that to happen, a signal has to be sent at just the right moment to the engine that drives the generator to produce the electricity – in other words, the genset has to start up. To guarantee that, a whole lot of skill and precision is required, especially where the wiring of electricity generator sets is concerned.

The wiring is the nerve and motor control system of a genset. It connects control units and measurement systems on the engine to the engine management, the genset's temperature control systems or the fire extinguishing systems. And they have a lot to cope with: temperatures as high as 120°C, electric currents of as much as several hundred amperes and voltages up to 400 V. To ensure they are able to do so, mtu wires up the units itself at the Friedrichshafen production plant.

Up to 350 working hours

It takes three people from two to three weeks to get every wire in its rightful place and joined up with the right connectors. That can be as much as 350 working hours in total. One such person is Holger Erdle. Just now he is standing in front of his workbench, totally absorbed in the wiring diagram and surrounded by an apparent confusion of tangled wires. But when you talk to him it quickly becomes clear that he is following a precise plan with that jumble of leads. He puts together the wiring harnesses that will subsequently be fitted to the genset, i.e. the engine and electricity generator set.

Wiring diagram is the basis

The basic guide for his work is a wiring diagram that is produced individually for each genset – because in project business no one genset is the same as another. Following the circuit diagram, Holger Erdle first cuts the wire to the required length and labels it with a wiring marker so that afterwards he will know precisely which wire goes where. "Most of our gensets are ordered with an acoustic enclosure that shuts out the engine noises as much as possible on a ship, for example," Erdle explains. "We install the electronics for all components – such as CO2 fire extinguishing systems, warning sirens, engine self-monitoring systems, engine management and pump control systems – in the empty enclosure."

Holger Erdle is doing a worker self-check. That involves using a measuring device to check that all cables are functional. This is the very last step to be taken before the genset is shipped to the customer.

Up to 800 cable cores per genset

But Holger Erdle's job is not confined to the workbench. Once the wiring harnesses are fully assembled he attaches them to the genset and connects them up to the control cabinet. Every wire is connected to the relevant sensors on the genset and neatly routed to the control cabinet. Each cable contains several differently colored cores, each of which is connected to a separate terminal. The mtu electricians have to connect up as many as 800 such colored cores on every genset – an exercise in painstaking patience in which they can allow themselves no mistakes. "With emergency backup gensets in particular, it could have serious consequences if there was a bad connection," relates Holger Erdle. "So our work has to be 100% accurate every time."

It is a job that demands patience and a very fine touch, because each contact has to be pinned separately into the connecting plug.

Metal marry-up

Once the electric systems in the acoustic enclosure are ready, the marry-up begins. The bride and groom – that is to say genset and enclosure – are pledged to follow a shared path. So the enclosure is lifted onto the baseframe of the genset and the two are joined as one. Once the engine and generator are inside the enclosure, the electricians only have 50 to 60 cm of space to move in and connect the engine's electronics to the genset's electronics. That takes about another 70 hours in a very cramped and sweaty workspace. Afterwards, the interfaces with the customer's own electronic systems are constructed. And no sign of the original confusion of cabling remains.

Point of contact

Dominic Roth
+49 7541 90 3455

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