Electrical Pics, Just for fun.

Harvey Ramer

Here are some pics from a new service install and controls to operate several overhead cranes. The service is 240v 1-phase and the crane required 480v 3-phase. Hence the controls to convert the power for the cranes.

JUGHNE

Looks good, that part of the building should stay warm.
Is that a motor/rotor inverter to produce 3 phase? Then how is it bumped up to 480?

I actually checked the NEC book of exceptions 230.28 B that the guy wires allow you to have a coupling above the roof flashing.

ratio

120/240 panel on the left, then to the rotary phase converter, through a contactor (to shut the panel off if the converter faults?), then through a step-up xfrmr & away to the crane.

That's a good-looking job. Why PVC?

Harvey Ramer

Yes, what looks like a motor sitting on the floor, is an idler generator made by Baldor. It generates the 3rd leg. It's digitally controlled and stable enough to run CNC equipment. The control box right below the phase converter control, automatically loads and unloads power from the converter and prevents it from being started under any load. Had to do it that way because it's connected to a 15kva transformer. The transformer is a dry type 480v Delta to 240v Delta. I back fed it to achieve my goal. Works like a top and is 1/3 the cost of a 240v to 480v.

Oh yes! The converter is remote start. That makes it convenient for using the crane.

Good eye on the coupling. I actually changed it to below the roofline because the engineer from the utility didn't like it. Why argue. It only took an hour.

ratio

Also, how'd they end up with the wrong voltage on the crane? Not available in 240 single phase? Or was there an "Oh, $h!t" moment?

Harvey Ramer

The power comes from the panel on the right. Through the phase converter, the the unloading control box, than the 3 phase panel on the left (over current protection), than the transformer and finally the crane.

I like PVC.

When you pick up a used 100k crane for 25k, this stuff makes sense.

j a_2

What way does it flow? Lol

Harvey Ramer

Towards low voltage. High voltage always flows to low voltage.

j a_2

So positive to negative or visa versa?

ChrisJ

What brand are those panels? Siemens?

Harvey Ramer

Yes, Siemens.

Solid_Fuel_Man

What kind of horsepower are the cranes? Was there stuff around used other than the crane? Any reason not to use a VFD to synthesize the 3ø we have done this on a number of occasions. The VFD has to be upsized significantly though. Was tge rotary converter a cheaper way to go.

Good looking install.

Harvey Ramer

Thanks!
There are actually 2 overhead cranes with a total of 8 motors. The accumulated HP is 6.5 The phase convector has the capacity to run up to 20 HP and start a single load up to 10 HP. I installed the three phase panel, as they will be adding more 3 phase accessories in the future.

I have used VFD's in the past to power and control 3 phase motors, with a single phase input. You are correct, they do have to be almost doubled in size. It is my understanding however, that you should really only run one motor off of the VFD. With that being the case, it was either a rotary or solid state. I would have loved solid state but I got a bad vibe from the company when I talked to them. So I ditched that and went with American Rotary. I know their product and people. They are 100%.

ratio

We looked at a rotary converter to fix an oh-****, but it was cheaper to eat the cost of new single phase equipment.

Zman

I am surprised it wasn't cheaper to buy trailer mounted 3 phase 480 generator.I guess every situation is different.

Harvey Ramer

> @Zman said:
> I am surprised it was cheaper to buy trailer mounted 3 phase 480 generator.I guess every situation is different.

I am assuming you mean a diesel powered generator?

This crane is a permanent fixture that will be used daily. The current setup has remote start which is essential for the mechanics using the crane. This way they don't have to walk to the other end of the building to start the converter, and they also don't have to leave it on while they aren't using the crane.
Diesel electric generation is expensive! The one Amish farmer was doing that to power his chicken barn. I converted him over to utility power and that gave him an extra $40k a year.

Zman

Harvey,
That makes perfect sense. The ones I have used were for construction sites.
A buddy of mine had a similar setup for a bunch of old wood shop equipment. The problem he had was that occasionally the antique rotary phase converter would fire up spinning backwards and blow the utility transformer on the pole.

Solid_Fuel_Man

Sounds like a bad or marginal start capacitor/capacitor bank. They are to split the single phase upon startup so the rotor "knows" which way to go. After that, it's all EMF which keeps things moving, therefore making the synthetic 3ø

Harvey Ramer

Wow! He definitely had something wrong with his setup. Could have been a combination of things, but the first things that come to mind is to much in rush current from improperly sized start capacitance, or starting the converter while under a load. I'm not sure how it would happen from the converter running backwards unless he tried to restart it before it came to a complete stop. If the converter is still coasting and you reapply power, and the rotation happens to be contrary to the converter direction, all hell will break loose! The ones like shown in the pic have electronics controlling that.

Utility transformers are not sized to the service amp rating. They are sized for typical loads. Our utility wants us to use soft start on any motor larger than 10 hp.

I have blown fuses on utility transformers before. I believe that was a 30HP motor and it did have a soft start.

I know a guy who put in a 400amp service. He ran parallel 4/0 for the entrance cable. He got his wires crossed and created a dead short. When he threw the double throw disconnect to the on position for the first time, the transformer literally exploded! Lucky no one was hurt.