High-Torque Drive Units for Heavy Mining Conveyors — From Single-Drive Gate Roads to Multi-Drive Main Haulage
The drive unit is where electrical power becomes belt tension. In a short plant conveyor, the drive is straightforward. In a long-distance underground coal conveyor — 3,000 metres of loaded belt moving at 4–5 m/s, carrying 3,000 tonnes per hour — the drive system is a significant engineering challenge. Starting torque, load sharing between multiple drive units, soft-start behaviour, and the ability to hold a loaded belt on a decline without runback are all design requirements that the drive unit must meet, not just the motor.
We supply gearboxes and complete drive units for mining belt conveyors across the power range from 250kW to 1,800kW per drive unit, produced to client drawings and specifications. Drive motors are supplied as part of complete drive unit packages where required.
Cylindrical-Planetary Gearbox Architecture
Large mining conveyor drives commonly use a compound gearbox combining cylindrical gear stages at the high-speed input with a planetary stage at the low-speed output. The logic is straightforward: cylindrical gear stages are reliable and well-understood, and handle the initial speed reduction efficiently at relatively modest torque levels. The planetary stage at the output handles the final reduction to conveyor head pulley speed at the full output torque — which, for a 1,000kW drive on a slow belt, can be in the range of 50,000–100,000 Nm or higher.
The planetary stage’s advantage at high torque is structural: the load is shared among three or more planet gears simultaneously, distributing the torque across multiple gear meshes rather than concentrating it in a single gear pair. This allows a compact housing to transmit torques that would require a much larger parallel-shaft gearbox. In underground coal mining, where equipment must be transported through roadways and installed in restricted headings, the size and weight advantage of a planetary output stage is not theoretical — it determines whether the drive fits the installation.
We produce both the cylindrical stages and the planetary assembly to the client’s drawing specification. Planet carrier geometry — the component that positions the planet gears and transmits the output torque — is a precision casting or forging produced to the dimensional tolerances that determine load distribution among the planets. Unequal load sharing due to planet carrier dimensional errors is a common root cause of premature planetary stage failures; we treat planet carrier bore position tolerance as a functional specification, not a nominal dimension.
Power Range and Application Matching
The power range we supply covers the main categories of underground and surface mining belt conveyor drives:
250–630kW: Gate road and panel conveyors in underground coal mines, shorter overland conveyors, plant feed conveyors. Single-drive configurations are common in this range. Starting torque requirements are manageable with direct-on-line or reduced-voltage starting for shorter, lighter-loaded conveyors.
630kW–1,000kW: Main haulage conveyors in underground mines, medium-length overland conveyors. Multi-drive configurations with two or three units sharing the load become common. Controlled start behaviour — either through CST (controlled start transmission) or variable-frequency drive — is typically specified to manage belt tension during starting on long, loaded conveyors.
1,000kW–1,800kW: High-capacity main haulage and trunk conveyors. A 3,000t/h conveyor at 3,000 metres might use two 500kW drives or three 400kW drives; a 4,000t/h system at 5,000 metres will typically use 1,000kW or 1,250kW units in a multi-drive arrangement. At these power levels, load sharing between drive units and dynamic behaviour during starting and stopping are engineering design issues that the drive unit specification must address.
CST and Variable-Frequency Drive Integration
CST (controlled start transmission) and variable-frequency drive (VFD) systems control the torque applied to the belt during starting, allowing long, heavily-loaded conveyors to be started under full load without the tension peaks that would otherwise require over-designed belt and structure. The gearbox in a CST or VFD-controlled drive system operates under controlled torque input from the drive system; the gearbox specification must be matched to the torque profile the drive system produces, not just the steady-state running power.
We produce gearboxes to client specifications that define the torque ratings, service factors, and interface dimensions required for integration with the specified drive control system. For clients specifying drive units for new installations, we can work from the conveyor design parameters — capacity, length, lift, belt speed — to confirm that the gearbox specification matches the drive system and conveyor requirements.
Supply Basis
Drive units are supplied to client drawings or specifications. We do not maintain a catalogue of standard units — the power range, reduction ratio, mounting configuration, and interface dimensions of a mining conveyor gearbox are specific to the conveyor design and the installation constraints. Custom production to the client’s specification is the normal supply basis, not selection from a standard range.
For clients replacing an existing drive unit, we can work from the nameplate data, dimensional drawings of the existing unit, or a combination of both to produce a replacement that fits the existing installation without modification to the conveyor structure. Where the existing unit’s drawings are not available, dimensional survey of the unit to be replaced is the starting point.
For drive unit enquiries, contact our engineering team with the conveyor parameters and gearbox specification or existing unit dimensions. See also: Belt Conveyor Components overview · Forging Capabilities · Machining Capabilities.