Belt conveyors move material all day in packaging lines, warehouses, foundries, food plants and bulk-handling yards. When the conveyor stops, the line stops, so the drive motor has to be sized and specified correctly from the start. For medium-length belts and loaded roller conveyors, a 7.5 HP 3 phase motor (5.5 kW) is one of the most common choices. In this guide we explain how to check whether 7.5 HP is right for your conveyor, which speed and mounting to choose, and how to protect the motor for long service life.

When Is a 7.5 HP 3 Phase Motor Right for a Conveyor?

Conveyor power depends on the load on the belt, the belt speed, the conveyor length, any lift (incline), and the friction in idlers, rollers and the gearbox. As a rule, the required power is the total belt pull multiplied by belt speed, plus the extra needed to lift material on an incline, divided by the efficiency of the drive train.

A 7.5 HP 3 phase induction motor typically suits:

• Medium-length horizontal belt conveyors carrying cartons, bags or loose material

• Inclined belt conveyors with moderate lift and load

• Roller and chain conveyors in packaging, bottling and dispatch areas

• Screw conveyors and bucket elevators of moderate capacity

• Transfer conveyors feeding crushers, mixers or packing machines

Always keep a margin of around 15–20% above the calculated running power. Conveyors are often overloaded in practice, belts get heavier when wet or dusty, and an undersized motor will run hot and trip. If your calculation comes close to 7.5 HP, moving to the next size up is usually the safer choice.

Choosing the Right RPM: 4 Pole vs 6 Pole

Conveyor drums turn slowly, usually between 30 and 100 RPM, so the motor always works through a gearbox, chain drive or belt drive. Choosing the motor speed decides the reduction ratio you need.

Example: a belt speed of 1 m/s on a 400 mm drum needs a drum speed of about 48 RPM (60 ÷ (π × 0.4)). With a 4 pole 1440 RPM motor, the gearbox ratio is about 30:1. With a 6 pole 960 RPM motor, the ratio drops to about 20:1.

• 4 pole (1440 RPM): the most common choice; compact motor frame, wide availability of gearboxes, good for general conveyors.

• 6 pole (960 RPM): more torque per HP at the shaft, a smaller gearbox ratio, and smooth running for heavy or slow conveyors.

• 2 pole (2880 RPM): rarely used on conveyors, as it needs a very high reduction ratio.

For heavy-duty or slow belts, our 7.5 HP 960 RPM 6 pole 3 phase foot mounted motor is a practical option. It pairs well with a worm or inline helical gearbox and reduces the load on the reduction stage.

Foot, Flange or Foot-cum-Flange Mounting

Mounting depends on how the motor connects to the gearbox and conveyor frame:

• Foot mounted (B3): bolted to a base plate and coupled to the gearbox with a flexible coupling, or driving through a chain or V-belt. Easy to align and replace.

• Flange mounted (B5): bolted directly to a flange-input gearbox. Compact, with no separate base or coupling alignment.

• Foot-cum-flange (B35): gives both options, useful when the drive layout may change or for extra support on longer frames.

For drives mounted on the conveyor head end, a flange motor with an inline helical gearbox saves space. For drives on the floor beside the conveyor, a foot mounted motor with a chain drive is common and easy to maintain.

Starting, Torque and Protection for Conveyor Motors

Conveyors often start fully loaded, for example after a power cut or an emergency stop. That needs good starting torque, so the starting method matters:

• DOL (direct on line): gives full starting torque; common on smaller conveyor motors where the supply can handle the starting current.

• Star-delta: reduces starting current, but starting torque also drops to about one-third. It works for conveyors that start empty or lightly loaded, and can stall a fully loaded belt.

• VFD or soft starter: gives smooth, controlled acceleration, reduces belt slip and shock on the gearbox, and lets you adjust belt speed.

To protect the motor in daily operation, we recommend:

• A correctly set overload relay matched to the motor's full load current on the nameplate

• Single phasing protection, since a lost phase on a loaded conveyor quickly overheats the winding

• Keeping the fan cover and cooling fins clear of dust and spilled material

• Checking coupling or chain alignment and tension regularly to protect motor bearings

• Greasing bearings at the recommended interval, without over-greasing

Why Choose Unicorn Engineers for Conveyor Motors

Unicorn Engineers is an induction motor manufacturer in Ahmedabad, Gujarat. We manufacture single phase and 3 phase AC induction motors in 2, 4, 6 and 8 pole speeds, with foot, flange, face and foot-cum-flange mountings, along with brake motors and crane duty motors. We are ISO and MSME certified, our motors come with a 1-year warranty, and we deliver across India with support for dealers and OEMs.

Whether you need one 7.5 HP motor for a replacement or regular supply for conveyor builders, our team can help you pick the right HP, RPM and mounting.

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• Visit us: 33, Gopal Charan Estate, Road No-5, Kathwada GIDC, Ahmedabad 382430

Tell us your conveyor length, load, belt speed and supply details, and we will suggest a suitable electric motor for your application. Phone and WhatsApp enquiries are always welcome.