Monday, June 6, 2011

How Electric Motor Winch Works

Basically electrical energy of a winch's motor is converted to rotational mechanical energy. This allows a cable wire or synthetic rope to be wound around it's drum, with the help of reduction gears to increase torque to pull or tow an attached object. This includes 4 wheel drives, SUV's, ATV's, to pull or tow large rocks, shrubs, felled trees, logs, and other vehicles. Portable winches are often used for manual clearance tasks, or attached to terrain based vehicles to aid in retrieval of mud stuck jeeps and ATV's or other off-road terrain vehicles. But like common electric DC (direct current) motors (e.g. car starter motor and electric drills), the principles of electromagnetism applies to generate rotation. This interaction results in the winding and pulling mechanism, of the humble but important and sometimes demanding role of the portable winch.

Inside Electric Winch Motor

The motor consists of coils known as the Armature or Rotor, housed within permanent magnets (or another coil set, i.e. series wound) referred to as a Stator (common on car alternators). Once an electric current is applied (switch on) into the motor, the stator setup induces a magnetic field, which causes rotation of the armature. Hence the attracting and repellent forces of the North-South orientation of the magnets creates motion. Depending on component construction, motors have different power output and torque, and coupled with it's gear reduction ratio, produces it's horsepower rating. This rating results in different speeds and line pull weight or power for a winch. Series wound motors tend to produce more power than the permanent magnet motors, often used for light to medium units, but can overheat, and subject to reduction in field magnet strength, though less current output is generally required.

Video Animation of Electric and DC Motors Working

Winch Gearing Train System

The gear arrangement allows more torque to be produced, of which the gearing reduces the relatively high speed of the motor to a lower speed. This reduces the work required for the motor, and with higher gear reduction, the more revolutions are required for rotation.
- Planetary gears are often used, and generally require a braking system to prevent free spooling.
- Spur gears, common in many applications, produce large reductions, are generally straight cut and mounted on parallel shafts. But are known to be noisy, require a braking process, and also seem to be occupy a relatively large area.
- Worm Gears - Require a clutch mechanism for free spooling, due to it's inherent ability of a self braking mechanism for heavier work loads. Though produces good reduction, a simpler arrangement (self braking), and perhaps more durable. Though line pull speeds are noticeably slower.
- Layer Effect - The line speed and pulling power can be be affected, being reliant on drum diameter, gear ratio, and spool diameter. Thus when reeling in, building up layers, reducing the net effect of gear reduction, resulting in lowered pulling power. This effect is pronounced with a narrow drum, i.e. quicker cable spooling, but faster reduction in pulling strength.

Video Animation of Planetary and Worm Gears

Power Supply Setup

Though gearing systems produce a lot of the work, having well maintained, and sometimes a enhanced electrical system, results in more efficient and easier electrical power transfer - when you might need it the most. Winches run of 12V or 24V DC power, and can include 2 to 4 solenoids, either integrated with the winch, or remote mounted. Batteries should have the minimum CCA rating (Cold Crank Amps), which should be provided with the winch, since a motor under heavy load could draw a few hundred amps. Or if dual batteries, and suitable alternator should be considered for extensive winch tasks (4x4 article). Then their are battery types to suit, e.g. if deep cycle, or marine rated.

Also the possibility (preference) of installing remote switches, e.g. a 350 amp switch for marine applications. Task dependent, convenience, and personal preference would come into effect, but generally standard winch kits should suffice for the average recreational 4x4 enthusiast, or simple towing tasks.


Understanding of electrical motors and different gear mechanisms, which need work together for maximum effect, might allow you subjectively evaluate and compare various brands of units. Knowing the advantages and specific features of the gear systems and motors, should help determine the most suitable unit for your task applications. This is important, particularly for demanding use, to select a suitable horsepower rated motor, and it's rated line pull strength, for a portable winch.


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