1, 2, 3 Phase!

The moment we’ve all been waiting for has come! We designed our whole building around this 5 ton Demag bridge crane we purchased two years ago.

Time to see if the crane actually works!

For those of you who are less familiar with things like “festoons”, here is a fun reference diagram I found online.

First, we had to spruce things up.


We finished bolting the rails to the top of the beams.

Then, John laboriously straightened out all of the bent steel brackets. (This required a propane torch and a lot of muscle.) The following day, Sam unpacked some boxes that came with the crane and discovered a brand new set of brackets. Oops! Sam and John begrudgingly removed the old brackets from the beams, and Sam welded the new ones in place.

Then the beams were ready for paint! Sam and John primed the bad spots first, creating a graffiti masterpiece in the process.

Then they sprayed the beams black, erasing all reminders of McDonald’s. The beams look new and sleek now and hopefully won’t rust.

Next, Sam and John assembled the conductor rails (the orange and green tracks).

They set up an electrical box on the crane beam and ran wires up to the conductor rails.

Inside of the blue box – yikes!

The conductor rails transmit electricity like tracks for a model train. But why are there four rails?

It’s because the bridge crane runs on three phase power (normal residential power is single phase). On a really basic level, single phase power is supplied with two powered wires, plus a neutral wire. Three phase power involves three powered wires (hence the three orange tracks and the green “ground” track).

Three phase power is more efficient and allows normal sized wires to be used to deliver high power. In some regions, it is possible to tap into the power company’s three phase power (at a cost), but that isn’t an option where we live. We had to get a phase converter. Like its name implies, a phase converter converts single phase power into three phase power.

The phase converter consists of a panel (left in photo below) and a motor (not pictured). Single phase power enters the phase converter panel, powers a motor, which “in turn”, creates a third power output.

The power then goes to the special circuit breaker panel (right in photo) for three phase power. This panel can be used for all of the three phase 240V tools in the shop. However, the 5 ton crane runs on 480V, so Sam purchased a transformer (of course!).

The transformer

This transformer has three coils since it is for three phase power. It doubles the output voltage for each wire, creating the 480V we need for the crane.

Sam hooked all of this up in a day or so, and mounted everything on a convenient little cart (that will eventually reside in the attic).

Front of cart – Phase converter on left, 3 phase breaker panel on right
Backside- Transformer on left, phase converter motor on right

Then we fired up the crane! We gave it a 50/50 chance of working, since it had been sitting in pieces on our property for two years (including a whole winter outside).

Guess what! It worked on the first attempt! Well, the bridge moved North and South, but the hoist wasn’t moving East and West. Sam climbed up to investigate and was pleased to discover that the motor was simply turned off. With one flip of a switch, the crane was working in all degrees of freedom.

We were in awe. Sam looked happier than a kid on Christmas morning!

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