Underground mining imposes requirements on electric motor specifications that surface installations do not.
The combination of methane-present atmospheres in coal operations, dust concentrations, continuous duty cycles and restricted maintenance access creates a specification environment where the Ex d rating, insulation class materials, and voltage availability of a motor carry real operational weight.
The TECO MAX Ex d range addresses these requirements with Group I certification, Class F insulation combined with low temperature rise, and availability to order up to 1000V. This is backed by local TECO ModShop capability in Australia and New Zealand, enabling non-standard configurations to be handled without returning to the factory.
TECO product manager – low voltage motors for Australia and New Zealand Atheer Yaseen Nashi discusses the technical specification and application context of the TECO MAX Ex d series.
What does Group I certification mean for the TECO MAX Ex d, and what does the certification scope cover?
AN: Group I refers to equipment intended for use in underground mines and their surface installations where the risk of firedamp, which is primarily methane, or coal dust is present. It is distinct from Group II, which covers above ground surface installations.
The MAX Ex d carries two certifications within Group I: Ex db I Mb and Ex db IIB T4 Gb. The Ex db designation is the flameproof protection concept, meaning the motor enclosure is designed to contain any internal ignition and prevent flame propagation to the surrounding atmosphere.
The I Mb classification is specifically for underground methane-risk environments, while the IIB T4 Gb certification extends the scope to surface hazardous area installations classified under Group II with the temperature class T4 (surface temperature ≤135°C).
Having both classifications within the one product certification broadens the range of installations the motor can be specified for without requiring a separate product selection.
The TECO MAX Ex d is stocked at 415V but available to order up to 1000V. What drives the 1000V requirement in underground mining?
AN: Underground mines have progressively moved to higher distribution voltages to reduce current levels and cable cross-section requirements at depth.
At 1000V, the current for a given motor power is roughly 40% of the current at 415V. In an underground installation where hundreds of metres of cabling runs from the substation to the working face or pump station, that reduction in current directly reduces voltage drop and copper losses in the cable, allowing lighter cable to be used for the same power delivery.
We stock the standard range at 415V for off-the-shelf availability, and the 1000V variants are available to order. For mining operations planning new installations or major refurbishments on a 1000V system, the 1000V TECO MAX Ex d slots directly into the distribution architecture without an intermediate transformer thus saving cost.
What modifications does the local TECO ModShop handle, and why does local accredited modification matter for underground operations?
AN: The TECO ModShop facilities in Australia and New Zealand are accredited to carry out modifications to Ex d motors while maintaining the certification integrity of the product.
The modifications that can be handled locally cover the practical range of non-standard requirements that come up in underground motor replacement: terminal box orientation changes to match existing cable entry positions, cable entry configuration changes including gland plate and conduit entry arrangements, anti-condensation heater installation, and shaft and mounting adjustments.
What are the most common underground applications for the TECO MAX Ex d across the power range available off the shelf?
AN: The off-the-shelf range covers 0.75kW to 110kW at 415V in heavy-duty cast-iron frames. The applications that sit within that range in a typical underground mine include conveyor drives, which are often the highest installed motor count in an underground operation, underground pump motors for dewatering and process water systems, ventilation auxiliary fans, and ancillary drives on mining machinery.
The 0.75kW to 110kW range covers most of these applications at standard underground distribution voltages. Motors above 110kW in the Ex d range are available to order from the factory.
When replacing an underground motor in a live operation, what specification checks should be completed before committing to a replacement?
AN: The certification scope is the first check. The replacement motor must carry the certification appropriate to the zone classification of the installation.
For Group I methane-risk underground environments, that means confirming the I Mb certification is present. The voltage rating must match the distribution system at the installation point, whether that is 415V or 1000V. Frame dimensions and shaft specification need to match the driven equipment to avoid modifications to the coupling and/or mounting arrangement, which adds time in an unplanned replacement situation.
The terminal box orientation and cable entry configuration need to match the existing conduit or cable tray arrangement, which is where the TECO Modshop becomes relevant if the standard orientation is not compatible. The duty cycle and load profile should be confirmed against the motor nameplate power to ensure the replacement is not undersized for the application. And the anti-condensation heater circuit, if one is present in the existing installation, needs to be confirmed as part of the replacement motor specification.
These are not unusual checks, but in the event of an unplanned underground replacement, they are the ones that most commonly cause a delay if left until the replacement motor is on site.
For a TECO MAX Ex d technical data sheet and certification scope document, visit the TECO website.
