Mining sites don't stay put. An open-pit operation keeps pushing its working face outward; an underground mine keeps extending its tunnels. The equipment drawing power today may be somewhere else entirely in six months — and a fixed substation, bolted to one concrete foundation, can't follow it. That gap is what a skid-mounted transformer is built to close.
A skid-mounted transformer is a transformer installed on a reinforced steel skid or base frame, built so the whole unit can be towed, lifted, or otherwise relocated when needed — not just rewired, but physically moved.
It can be supplied on its own, or bundled with switchgear, protection and control systems, and metering to form a complete mobile substation. The terms get used loosely: "skid-mounted transformer" usually refers to the transformer and its mobility setup, while "mobile substation" refers to the fuller package. You'll also see it called a mining mobile transformer, portable substation, or transformation sled — different names for the same idea.
Electrically, it's a standard transformer: medium-voltage power comes in, gets stepped down, and is distributed to pumps, fans, conveyors, drills, and crushers. What's different is that the unit can be towed closer to wherever the active working area is, rather than staying fixed for its entire service life. Because it's built to move, the skid frame, lifting points, and cable connections need to hold up under repeated transport and vibration, not just day-to-day operation.
Oil-Immersed or Dry-Type?
Both are used, depending on the site. Oil-immersed units suit applications needing higher capacity and efficient cooling. Dry-type units, particularly cast-resin ones, get chosen where the absence of insulating oil matters more — fire risk, ventilation limits, or environmental concerns. The right choice depends on voltage, capacity, load profile, and site conditions.
One clarification: "skid-mounted" describes how the unit is installed and moved — it says nothing about explosion protection. In underground coal mines or other hazardous areas, methane and coal dust classification bring their own additional safety requirements.
Where It's Used?
Open-pit mines — the most common case. As the pit expands, shovels, drill rigs, conveyors, and pumps keep shifting, and a fixed substation gradually ends up too far away. Many sites run a main substation plus smaller mobile units that follow individual working areas.
Underground mines — space is tighter, but the problem is the same: the working face advances, and equipment needs to be compact enough to move with it. Mobile power centers typically feed continuous mining equipment, pumps, ventilation fans, and conveyors, with additional protection and enclosure requirements for hazardous environments.
Dewatering — large pumps clear groundwater from active areas, and as those areas shift, a mobile transformer can move with the pumping system instead of running off a long fixed cable.
Construction and tunnel projects — shaft sinking and tunnel excavation involve a working face that moves forward over time. Instead of building and tearing down fixed installations at every stage, the mobile unit moves with the project.
A Note From Our Own Experience
We've supplied this type of unit for mining projects in the Philippines.
If you plan to purchase this product, pls feel free to contact us!
