Explosive atmosphere motor for use in underground mining
31 May 2015
An extension to ABB’s low voltage IEC mining motors range is now available with Ex d flameproof protection for use in underground mine (group I) applications such as conveyors, air handling fans and water pumps.
Rated from 0.55 to 710kW in frame sizes IEC 80 to 450, the cast iron motors are an evolution of ABB’s long-life explosive atmosphere range. This range has been used for decades in group II and group III surface industries such as oil & gas and marine. The hazardous area motors, type code M3JP, are certified to IECEx and ATEX. The motors operate to the latest IEC standard efficiency levels, IE2, IE3 and IE4.
Available from two to eight pole pairs, higher pole combinations or two-speed motors are available on request. The motors feature an IP66 enclosure for maximum protection against the ingress of high pressure water, dust and volatile substances and are insulated to class F. Higher class H (180°C) is available as an option. Depending on frame size, the motors have a cast iron or steel fan; a more robust choice than the plastic fans used in less demanding applications.
The rotor and stator of the orange-coloured motors have special varnish corrosion protection that enhances the reliability by preventing moisture ingress between laminations and the winding insulation. An optional space heater is available to keep the motor’s internal temperature above ambient, thereby avoiding condensation. Safety and reliability is further enhanced with the use of PTC type winding temperature detectors.
Labyrinth bearing seals offer improved protection against moisture ingress than traditional rubber lip seals. The design features two discs, shaped like interlocking fingers, the space between which is filled with grease. When the bearing spins it acts like a carousel, further ensuring that water ingress is avoided due to the centrifugal forces. The labyrinth seal is maintenance-free, unlike traditional sealing methods, which need to be replaced.
The use of stainless steel for the rating plate, nipples and bolts offers enhanced corrosion protection. In addition, the bolt heads feature a shroud to protect against falling rocks or stones damaging or inadvertently unwinding the bolts.
The motors are designed for use with variable-speed drives (VSDs) without the need for any additional filters. However, reinforced insulation is available for VSD use above 500 V. When using a VSD other considerations include bearing insulation, a VSD-specific rating plate and surface temperature protection detectors.
A series of optional features, depending on application, include roller bearings on the drive end, up to frame size 315, suitable for belt driven applications and separate cast iron terminal boxes for instrumentation and heaters.
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