A gantry crane travels further than any machine in the plant, and the power has to follow it. Transformer, cable, reel and earth, measured on the runway rather than on the nameplate.
A gantry crane is the one machine in a plant where power has to travel as far as the load does. The hoist lifts twenty metres. The runway may be three hundred. Almost everything that goes wrong electrically on these machines goes wrong somewhere along that run, and almost none of it is in the crane quotation.
The numbers below are for a 100 tonne machine on a 300 m runway, the size we build most often for precast yards and steel stockyards. It draws 204 A at 400 V. That is three percent of voltage gone over 200 m of 150 mm² cable, six percent over 400 m, and a four layer cable reel takes the same cable down from 404 A to 227 A before you have even considered a hot afternoon. Six percent is where drives start tripping on undervoltage during a hoist start, so the whole electrical design of a long runway comes down to keeping that one number under about five.
Start with the only figure that matters and is almost never printed in a brochure: the current at the point where the runway cable connects. Motor nameplates do not give it, because they are per motor, and a gantry crane has four or five of them.
Add the hoist, the trolley, and both legs of the long travel, then convert with the usual three phase relationship. For a 400 V machine at 0.85 power factor and 0.90 motor efficiency, the divisor is 530, so amps equals kilowatts divided by 530 and multiplied by a thousand. The table uses our own standard configurations, which means these are SIEC planning figures rather than catalogue data — a heavier duty machine with bigger travel drives will sit above them.
| Capacity | Hoist | Trolley | Long travel | Installed | Current at 400 V |
|---|---|---|---|---|---|
| 5 t | 7.5 kW | 1.5 kW | 2 × 1.5 kW | 12.0 kW | 22.6 A |
| 10 t | 13.0 kW | 2.2 kW | 2 × 2.2 kW | 19.6 kW | 37.0 A |
| 16 t | 18.5 kW | 3.0 kW | 2 × 3.0 kW | 27.5 kW | 51.9 A |
| 20 t | 22.0 kW | 3.7 kW | 2 × 3.7 kW | 33.1 kW | 62.4 A |
| 32 t | 30.0 kW | 5.5 kW | 2 × 5.5 kW | 46.5 kW | 87.7 A |
| 50 t | 45.0 kW | 7.5 kW | 2 × 7.5 kW | 67.5 kW | 127.3 A |
| 100 t | 75.0 kW | 11.0 kW | 2 × 11.0 kW | 108 kW | 203.6 A |
Two things stand out. A hundred tonnes of lifting capacity is only eight times the current of twelve tonnes, because the hoist speed drops as capacity rises. And half the plant's crane capacity sits in the long travel drives on the big machines, which surprises people who assume the hoist dominates.
Port engineers move to 6.6 kV or 11 kV for gantry machines, and buyers of industrial gantry cranes read that and ask whether they need it too. They almost never do, and the reason is arithmetic rather than policy.
A published transformer study for container terminals puts the same calculation on a 1,400 kVA ship-to-shore crane fed over 400 m. At 400 V it draws 2,021 A, needs four parallel 240 mm² cables per phase, and still drops about 9 percent at full load. At 6.6 kV the same crane draws 122 A through a single 95 mm² cable and drops 0.27 percent.
| Machine | Installed | Current at 400 V | Cable over 400 m | Drop at full load |
|---|---|---|---|---|
| 100 t industrial gantry | 108 kW | 204 A | 1 × 150 mm² (6.0%) | 6.0% |
| Same, one size up | 108 kW | 204 A | 1 × 240 mm² (4.3%) | 4.3% |
| STS container crane | 1,400 kVA | 2,021 A | 4 × 240 mm² per phase | 9.0% |
| STS, at 6.6 kV | 1,400 kVA | 122 A | 1 × 95 mm² | 0.27% |
Read the copper, not the voltage. The port crane needs twelve 240 mm² conductors per phase group, roughly 26 kg of copper for every metre of quay, and a reel or conductor line built to carry it. Our 100 tonne machine needs one cable and about 3 kg. Medium voltage is not a virtue on its own; it is a way of not dragging a quarter of a tonne of copper along a berth.
Where the industrial case does flip is a shipyard or a multi-crane bay fed from one runway bus, and where the transformer has to sit a long way from the crane because there is no space at the runway end. Both add cable length rather than capacity, and both are worth costing properly before you accept a 6 percent design.
Not the installed kilowatts. A crane spends part of every cycle waiting, and its drives are never all at full power at once, so the transformer is sized on the ten minute RMS current and not on the sum of nameplates.
The container terminal study is explicit about this: crane demand factors of 0.40 to 0.50 on installed kVA are normal for a working fleet, and transformers are then specified at 1.15 to 1.3 times the ten minute RMS. It also makes the point that the winding must stay below its hot spot limit through the whole shift, 98 °C for normal cyclic life under IEC 60076-7, rather than just through the twenty second hoist peak. A cast resin unit with a thirty to sixty minute thermal time constant barely notices that peak.
| Capacity | Installed | Duty factor | 10 min RMS | × 1.25 | Specify |
|---|---|---|---|---|---|
| 5 t | 12.0 kW | 0.45 | 6.4 kVA | 8.0 kVA | 10 kVA |
| 10 t | 19.6 kW | 0.45 | 10.4 kVA | 13.0 kVA | 15 kVA |
| 16 t | 27.5 kW | 0.48 | 15.5 kVA | 19.4 kVA | 25 kVA |
| 20 t | 33.1 kW | 0.50 | 19.5 kVA | 24.4 kVA | 25 kVA |
| 32 t | 46.5 kW | 0.50 | 27.4 kVA | 34.2 kVA | 40 kVA |
| 50 t | 67.5 kW | 0.55 | 43.7 kVA | 54.6 kVA | 63 kVA |
| 100 t | 108 kW | 0.55 | 69.9 kVA | 87.4 kVA | 100 kVA |
Our duty factors run a little higher than the port figures, 0.45 to 0.55 rather than 0.40 to 0.50, because one industrial gantry crane often does the work of a whole bay: unloading, feeding the saw, moving to the paint line. If your machine has a genuine duty class of A6 or above, take the upper number and add a step. These are planning figures, not measured data, and the honest way to replace them is to log a week of current on the finished machine.
On price, a cast resin transformer in this range is not the budget problem people fear. Chinese factory pricing for 100 kVA cast resin units sits in the low thousands of dollars, and the general benchmark for small distribution transformers is 18 to 30 USD per kVA. What costs money is being wrong: a transformer bought one size too small, run at 40 °C ambient in a steel enclosure, will spend its life at its hot spot limit.
Yes, and this is where a crane differs from every other load on the plant. The drives are the harmonic source that decides the transformer design, and the numbers are not subtle. A six pulse thyristor or diode front end produces 25 to 35 percent current THD. Twelve pulse halves it. An active front end brings it to 4 to 8 percent.
| Front end | Current THD at full load | What it does to a standard transformer |
|---|---|---|
| 6 pulse, no reactor | 25–35% | 10–20% of usable capacity lost to eddy current heating; specify K factor or IEEE C57.110 derating |
| 6 pulse with 4% line reactor | roughly halved | A K-13 unit copes without derating; cheapest single fix on the machine |
| 12 pulse | half of 6 pulse | Needs a phase shifting transformer or two drives; rarely worth it below 100 kW |
| Active front end | 4–8% | Standard transformer is fine; adds regeneration, which matters on the hoist |
Two practical consequences. If the crane shares a transformer with anything sensitive, a welding bay or a PLC controlled line, the harmonic question stops being about the crane and becomes about the neighbour. And if the site already has a generator for backup, remember that harmonic voltage distortion is inversely proportional to the source strength, so a standby set makes the same crane look far worse on paper than the grid does.
We size the drives on the machine and the transformer with a K factor on the order sheet. If you want the full harmonic treatment rather than the transformer view, our gantry crane specification sheet lists the standard drive options per capacity.
The most common specification error on a long gantry is a festoon system, because it is the cheapest metre of hardware in the catalogue and the buyer has seen it on every workshop crane. It is also the system that stops working somewhere around 80 metres.
| Property | Festoon | Conductor rail | Cable reel |
|---|---|---|---|
| Practical travel | 50–80 m, 150 m with intermediate supports | 500 m and beyond | 100 m spring, 400 m and beyond motor driven |
| Travel speed | up to 100 m/min | up to 300 m/min | 60 m/min spring, 120 m/min motor |
| Current | 20–630 A | 50–2,000 A | 20–630 A spring, 500–2,000 A motor |
| Hardware cost | EUR 25–60 per metre; USD 60–180 installed | EUR 60–200 per metre; USD 80–400 installed | EUR 40–150 per metre |
| Service life | Cable 3–8 years | Rail 15–20 years, shoes annual | Reel 10–15 years, cable 3–6 years |
| Maintenance | 6 months, trolley bearings and clamps | Annual, collectors and joints | 6–12 months, drum and slip ring |
| Dust and heat | Poor in dust, cable life falls above 60 °C | Good; enclosed profile to 120 °C | Good, sealed drum |
The crossover is not a matter of taste. Below 70 m all three work and you should choose on other grounds. Between 70 and 100 m a festoon needs intermediate supports, which usually kills its cost advantage. Above 100 m only a conductor rail or a motor driven reel is practical, and above 100 m/min of travel speed the rail is effectively mandatory because festoon cables start whipping and the trolley track takes the beating.
On a 200 m precast yard runway, a rail costs more up front and roughly a fifth of the cable replacement work over twenty years. A motor driven reel costs less to install, especially where there is no room for rail supports along the stock lanes, and it is the better answer when the runway will be extended or re-laid in a few years. Both are defensible. What is not defensible is 200 m of festoon and a maintenance budget.
Because heat cannot leave. A cable lying on the ground sheds heat into air on three sides. Forty turns of the same cable wound on a drum shed heat into each other, and the inner layers run hot enough to age the insulation decades early.
The standard treatment is unfriendly to optimism. Under DIN VDE 0298-4, a reeling cable rated 352 A on the ground and 370 A suspended gives 282 A with one layer on the drum, 172 A with three layers, and 147 A with five. ICEA tables used in mining are blunter still: 85, 65, 45 and 35 percent for one, two, three and four layers.
| Layers on the drum | 1 | 2 | 3 | 4 |
|---|---|---|---|---|
| DIN VDE 0298-4 factor | 0.80 | 0.61 | 0.49 | 0.42 |
| ICEA factor | 0.85 | 0.65 | 0.45 | 0.35 |
| 50 t crane, 127 A, needs a ground rating of | 159 A | 209 A | 260 A | 303 A |
| 100 t crane, 204 A, needs a ground rating of | 255 A | 334 A | 416 A | 486 A |
Take the 40 °C ambient factor of 0.89 as well, because an outdoor yard in summer is not a 30 °C test cell, and the 100 tonne machine on four layers needs a cable rated 546 A on the ground. That is a 300 mm² three core, which weighs about 11 kg per metre with its sheath. Four hundred metres of it is 4.7 tonnes on one drum, and now the reel is a structural project rather than an accessory.
This is the point where the electrical engineer and the mechanical engineer are forced to talk. The cable that solves the voltage drop is often the cable the reel cannot carry, and the answer is either a rail, a shorter drum, or accepting a bigger drop.
Run the standard calculation with the reactance term included, because on 150 mm² and above the reactive part stops being negligible. Using IEC 60364-5-52 Annex G values, resistivity 0.0225 ohm mm² per metre for copper in service and 0.08 milliohm per metre of reactance, 0.85 power factor:
| Crane | Current | Cable | 100 m | 200 m | 400 m |
|---|---|---|---|---|---|
| 5 t | 22.6 A | 16 mm² | 1.2% | 2.4% | 4.8% |
| 20 t | 62.4 A | 50 mm² | 1.2% | 2.3% | 4.6% |
| 50 t | 127.3 A | 95 mm² | 1.3% | 2.7% | 5.4% |
| 100 t | 203.6 A | 150 mm² | 1.5% | 3.0% | 6.0% |
The design limit is 5 percent for a motor feeder supplied from a public low voltage network, with 3 percent reserved for lighting, and 8 percent where the installation is fed from a private transformer. IEC 60364-5-52 Annex G does allow an extra 0.005 percent per metre beyond 100 m, capped at 0.5 percent, which sounds generous until you do the arithmetic: the cap is reached at 200 m and it will not rescue a 6 percent design.
So the 400 m column is the one that decides the cable. A 100 tonne machine on a 400 m runway needs 240 mm² to get to 4.3 percent, and at that size the jointing, the bending radius and the reel weight all become the project. This is the moment to think about where the transformer goes instead of how thick the copper is.
Feed position is free design work and it buys more than a cable size. Voltage drop is proportional to the length the current actually travels, so feeding at the middle halves it, and two feed points cut it to a third.
| Feed arrangement | Effective length | 100 t, 400 m runway | What it costs |
|---|---|---|---|
| End feed | 100% | 6.0% at 150 mm² | Cheapest cable route, largest cable |
| Centre feed | 50% | 3.0% at 150 mm² | A cable route to the middle of the runway, or a rail fed at mid span |
| Two feed points at thirds | 33% | 2.0% at 150 mm² | Two isolators, interlocked; a rail is easier than a reel here |
| Three feed points | 25% | 1.5% at 150 mm² | Sectionalised bus, protected joints, more to inspect |
A centre feed on a 400 m runway is worth two cable sizes, and it costs a trench and a length of armoured cable. The catch is isolation: every feed point needs a lockable disconnector, and the crane supply switch must be reachable by whoever is working on the machine. On a rail system the feed points are also joints, and joints are where voltage drop and corrosion both concentrate.
No, and this is the second most expensive assumption in an export order. IEC 60038 sets the preferred nominal values and, usefully for buyers, also records what still exists in the field.
| System | Frequency | Status | Where you meet it |
|---|---|---|---|
| 230/400 V | 50 Hz | Preferred | Most of Europe, China, Middle East, most of Asia and Africa |
| 220/380 V | 50 Hz | Superseded, still exists | Older plants in Asia, parts of Latin America |
| 240/415 V | 50 Hz | Superseded, still exists | UK legacy, Australia, parts of Africa and the Gulf |
| 277/480 V | 60 Hz | Preferred | North America industrial |
| 347/600 V | 60 Hz | Preferred | Canada, some US heavy industry |
| 400/690 V | 50 Hz | Preferred | Large plants, mines, some ports |
The migration from 220/380 to 230/400 was required to land inside plus six minus ten percent, and from 240/415 inside plus ten minus six percent, with a deadline that passed in 2003. Twenty three years later, plenty of plants still run the old values, which is why the first question on any enquiry should be a measured line to line voltage at the crane supply point and not a nominal one.
At the utilisation end, IEC 60038 puts the lowest acceptable utilisation voltage for a 230/400 V system at 196/340 V. That is the standard's floor, not a design target. Crane contactors are less forgiving than the standard: a drop of 15 to 20 percent is enough to make them chatter, and a chattering travel contactor on a loaded gantry is how you get a runaway.
The motor decides. Torque is roughly proportional to the square of volts per hertz, so the nameplate voltage and frequency have to be read as a pair, and this is where export orders go wrong even when the voltage looks close enough.
| Supply | Volts per hertz | Torque against a 400 V / 50 Hz motor |
|---|---|---|
| 400 V, 50 Hz (reference) | 8.00 | 100% |
| 380 V, 50 Hz | 7.60 | 90% |
| 415 V, 50 Hz | 8.30 | 108%, but the core is saturated and runs hotter |
| 480 V, 60 Hz | 8.00 | 100% torque, 20% more speed and power |
| 440 V, 60 Hz | 7.33 | 84% |
| 400 V, 60 Hz | 6.67 | 69%, and the hoist will not lift its rated load |
The reverse case is equally awkward and better documented. US Motors publishes derating factors for running a 60 Hz motor on 50 Hz: at 380 V a TEFC motor delivers 0.80 of its nameplate horsepower, at 400 V 0.75, and at 415 V 0.70. Their worked example is a 10 hp 4 pole 50 Hz 380 V requirement, which needs a 15 hp 60 Hz motor. Speed falls to five sixths, which the buyer notices on a gantry because long travel speed is the cycle time.
On a variable frequency drive the motor is fed by the drive rather than the grid, so frequency is set in a parameter and the mismatch mostly disappears. It does not disappear entirely: the brake coil, the panel fans, the control transformer and the limit switch cams are all still grid devices. If you are ordering from China for a 60 Hz country, say so on the enquiry and say which frequency the control circuit should be built for.
It needs an earth path, and the rails are not it. This is the same argument as the wheel-path question on a jib crane, only harder to fix later, because on a gantry the rail joint is a bolted or clamped connection sitting outdoors in dust and rain.
Chinese practice is the most specific and worth knowing even outside China. GB 50057-2010 requires earthing resistance of 4 ohm or better for a Category 2 structure, with 10 ohm permitted for repeated earthing. Conductor rails must be earthed at both ends and tied to the earthing grid every 30 m along the run. Rail joints must be bridged with at least 16 mm² copper, each bond under 0.03 ohm, and an earthing connection point is expected at intervals no greater than 25 m. The transition resistance between any crane component and earth must be 4 ohm or less.
| Item | Requirement | Source |
|---|---|---|
| Earthing resistance, Category 2 structure | 4 ohm or less; 10 ohm for repeated earthing | GB 50057-2010 |
| Rail joint bonding | ≥ 16 mm² copper, bond under 0.03 ohm | GB 50057-2010 |
| Earth connection interval | Rail earthed both ends, every 25–30 m along | GB 50057-2010 |
| Lightning earth continuity | Under 10 ohm; above that, bond to the earth network with ≥ 70 mm² | UK CPA TIN 036, BS EN 62305-1 and -3 |
| Foundation electrode | Round steel ≥ 10 mm, or galvanised strip ≥ 30 × 3.5 mm | DEHN foundation earth practice, EN 62305-3 |
| Ring earth mesh where an LPS is installed | ≤ 10 × 10 m in soil, bonding mesh ≤ 20 × 20 m in slab | EN 62305-3 (VDE 0185-305-3) |
Whether you add a lightning rod is a separate question. GB 50057 does not mandate one on an outdoor crane, but it does require that earthing be good and that the rails be reliably earthed. If the crane is the tallest thing in an open yard, a rod on the end carriage protects the machine's own panels and drives, and it is cheap compared with a drive replacement. What the standards are unanimous about is this: the crane structure and the rails may form part of the earth path, but you may not rely on them alone as the protective conductor.
Three things bite on a gantry more than on an indoor crane, and they are all about water and residual current.
Enclosure rating first. IP54 is the usual figure for indoor factory cranes, IP55 is the practical minimum outdoors where rain and condensation both arrive, and coastal yards want IP65 and stainless hardware. IEC 61439-1 makes the declared IP part of the assembly's verified characteristics, which means it has to be proven on the finished panel rather than inferred from the components inside it.
Second, the residual current device. A crane with a variable frequency drive can produce smooth DC residual current under a fault, and a Type AC or Type A device cannot see it. Type B is the only correct choice, and the standard advice for cranes is a super-immunised variant because ordinary Type B devices nuisance trip on drive leakage. The 30 mA instantaneous device belongs on final circuits feeding portable equipment, not on the crane supply: a crane is not a portable appliance, and tripping its supply can cause an uncontrolled movement.
Third, the crane supply switch and disconnector arrangement, which IEC 60204-32:2023 treats at length. The standard starts at the crane supply switch and explicitly includes conductor bars and festoon systems outside the machine, so the electrification method is inside the electrical safety scope and not a separate civil item. It also requires transformer protection against overcurrent and against excessive temperature rise if the secondary is shorted, with only three narrow exceptions to overcurrent protection on the transformer secondary leads: adequate conductor capacity, length not more than 3 m, and mechanical protection.
Below is the distribution of electrical faults across the gantry cranes we have commissioned and serviced, grouped by first cause. These are our own service records, not a published statistic, and the sample is small enough that you should read it as a ranking rather than a rate.
| First cause | Share | What it looks like on site |
|---|---|---|
| Supply voltage mismatch or wrong transformer tap | 21% | Drives trip on undervoltage under load; measured voltage 5–8% below nameplate |
| Undersized conductor rail or worn collectors | 18% | Long travel slows at the far end; shoe arcing and blackening at joints |
| Cable reel layer overheating | 17% | Soft or cracked sheath on inner layers; smell of hot rubber after a long travel |
| Missing rail joint bonding | 14% | Earth loop impedance high; RCD trips when the machine is wet |
| Wrong RCD type on a drive-fed crane | 12% | Nuisance tripping at random, worse in humid weather |
| Panel condensation and low IP rating | 10% | Corrosion on terminals, heater failed, water marks inside the door |
| Phase sequence and control wiring | 8% | Travel runs backwards; limit switch acts on the wrong side at commissioning |
Note what is not on the list: transformer failure, cable failure and drive failure, the three things buyers worry about. Almost everything above is a commissioning or specification error, which means it is preventable with a multimeter and a one page checklist, and almost none of it is covered by a warranty claim because the machine did work at handover.
The order below is by return on effort, from the things that cost nothing to the things that cost a transformer. The last row is a deliberate counterexample.
| Action | Cost | Effect |
|---|---|---|
| Measure the real supply voltage and set the transformer tap | Engineering time only | ±5% of voltage recovered, removes the single largest first year fault |
| Bond every rail joint and add repeated earthing | USD 300–1,500 | Fixes the earth path and stops wet-weather RCD trips |
| Move the feed to the centre of the runway | USD 2,000–8,000 | Halves the drop, worth two cable sizes |
| Increase the runway cable one size | USD 1,500–6,000 | 1.5 to 1.7 percentage points off the drop; recheck the reel rating first |
| Fit a 4% line reactor to each drive feed | USD 200–600 | Cuts current THD by roughly half and restores transformer capacity |
| Replace festoon with a conductor rail on a runway over 150 m | USD 4,000–20,000 | Removes a cable replacement every 3–8 years and the high-speed whipping problem |
| Buy a larger transformer | USD 3,000–15,000 | Does not fix a drop that happens downstream of it; fixes nothing measurable unless the transformer is genuinely overloaded |
That last row catches more buyers than any other item on this page. A 6 percent drop at the far end of a 400 m runway is caused by the 400 m, not by the transformer, and no amount of kVA at the near end will change the voltage at the far end. Order the transformer on RMS current, order the cable on drop and derating, and order the feed position on arithmetic.
Ten lines. Every one of them changes the price, and none of them is a specification a supplier can guess.
Line one is the one that saves the most money, and it is the one most often answered with the word "standard". There is no standard voltage. There is the voltage at your switchboard, measured, on the day the machine is commissioned.
About 63 kVA for a 400 V machine with 67.5 kW installed and a duty factor of 0.55, which gives 43.7 kVA of ten minute RMS current and 54.6 kVA after the 1.25 multiplier. Round up to the next standard size. That is much smaller than most buyers expect, and the reason is that a crane is not a continuous load: it spends part of every cycle waiting and never runs all its drives at full power at once. Our gantry crane order sheet asks for the duty class precisely so this number can be calculated rather than guessed, and the calculation belongs on the datasheet with the transformer.
Yes, with a caveat. Torque rises by about 8 percent because volts per hertz goes from 8.00 to 8.30, and the motor runs hotter because the core is closer to saturation. That is normally acceptable, since IEC 60038 allows a 230/400 V system to sit at 440 V at the supply terminals. Set the transformer tap to match the measured voltage rather than leaving it on the factory setting, and check that the control transformer and brake coils are rated for the higher figure.
One of the two, and a festoon is not an option at that length. Above 100 m the practical choices are a conductor rail, rated to 500 m and beyond, or a motor driven cable reel, rated to 400 m and beyond. Choose the rail where travel speed exceeds 100 m/min, where the yard is dusty, or where several cranes share the runway. Choose the reel where there is no room for rail supports, where the runway may be re-laid, or where a plug-in connection at the block ends is operationally useful.
Almost always because the device is the wrong type. A drive can produce smooth DC residual current during a fault, which Type AC and Type A devices cannot detect, and ordinary Type B devices trip on the normal leakage of a drive with a long motor cable. Fit a super-immunised Type B device, check the discrimination with the upstream device, and move any 30 mA instantaneous protection to the final circuits feeding hand tools rather than the crane supply.
Not always, but it always needs a defined earth path. GB 50057-2010 does not mandate a rod on an outdoor crane, while requiring earthing of 4 ohm or better and reliable rail earthing with joints bonded at 16 mm² or more. If the crane is the tallest structure in an open yard, a rod on the end carriage is cheap insurance for the panels and drives, and the earth continuity should be measured below 10 ohm, with a bond of at least 70 mm² to the site earth network if it is not.
Only with derating, and the derating is significant. US Motors publishes 0.80 for a TEFC motor at 380 V, 0.75 at 400 V and 0.70 at 415 V, which means a 10 hp requirement needs a 15 hp motor. Speed drops to five sixths, so long travel on a gantry gets slower and the cycle time changes. If the crane has variable frequency drives the motor side is handled by the drive, but the brake coils, panel fans and control transformer are still grid devices and have to be ordered for the correct frequency.
Related articles:
Jib Crane Slip Ring: What Four Wires Have to Cross Before the Hoist Moves, 0.125 to 5 Ton
Traveling Jib Power Supply: The Three Moving Joints Nobody Draws, 0.125 to 2 Ton
Suspension Crane Power Quality: Why an Underhung Crane Is Really Part of the Building, 0.5 to 5 Ton
Crane Harmonic Distortion: What Five Drives on One Busbar Do to a Double Girder, 5 to 100 Ton
Gantry Crane Runway Carbon: What Two Rails Cost Before the Crane Arrives, 5 to 100 Ton