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Planetary Gears, Worm Gears And Industrial Inverters In Industrial Machinery

Updated on August 18, 2013

Planetary Gears

Gearboxes come in a number of alignments, each suitable for slightly different industrial applications. A gearbox containing a planetary gear system (a special type of epicyclical gear) has a number of advantages over other gear trains due to its unique solar system-esque configuration.

In a planetary gearbox a ring gear encompasses planet gears which, in turn, orbit the sun gear. Whilst simple configurations include just one of each gear element, compound planetary gears use meshed or stepped planet gears to improve torque to weight ratios and flexibility.

Planetary gearboxes have a number of advantages over traditional industrial gearboxes. Not only are they extremely compact, the configuration allows even load distribution over the gears. This distribution allows for greater torque capabilities and an increased stability, which is crucial in many industrial applications. Torque density and load ability can both be increased by simply adding more planet gears to the system.

Perhaps the most appealing characteristic of a planetary gearbox however is its extremely high efficiencies. With typical losses amounting to just 2 or 3% per stage, planetary gear configurations are second to none in converting energy from input to output, something extremely desirable in industry.

Their compact size, high efficiencies, high torque to weight ratios and operational stability make planetary gearboxes useful across a wide range of industries including steel and metalworking, construction and even the food and chemical sectors. In particular, planetary configurations lend themselves well to industrial slewing drives used across all of these sectors.

Specific examples of planetary gearbox applications include machine tools, such as lathes or milling machines, cranes and even automotive gearboxes. Some automatic transmission systems work by placing multiple planet and sun gear units inside the same annulus (ring gear) to combine the output of the first stage with the input of the second stage in order to increase or decrease the gear ratio.

There are several disadvantages to planetary gear systems although through clever engineering design these are usually fairly simple to offset. The main disadvantages include the inaccessibility to planetary gearboxes due to their complex design and the fact that gears must be mounted in line with input and output shafts to avoid any further gearing requirements.

To summarise, planetary gears are particularly useful in a number of industrial gearbox applications due to their compactness and high torque to weight ratios, high efficiencies and resistance to shock. Despite their often complex design, gearboxes housing planetary gear systems are widely used across manufacturing, construction, automotive and even food and chemical industries.

Worm Gears

Gearboxes come in a number of alignments, each suitable for slightly different industrial applications. The worm gearbox has a number of advantages over its contemporaries with its unique configuration ideal for a number of specific industrial usages.

A worm gear consists of two perpendicular elements: a screw (known as the worm) and a single helical gear (known as the worm gear). The worm is the driving element in the configuration, rotating the worm gear in either a clockwise or anti-clockwise fashion. This 90° meshing and the lead angle of the gear provide one of the major advantages of a worm gear, self-locking.

The term ‘self-locking’ is used to refer to the fact that the power transmission in a worm gear is one directional; the worm will always drive the worm gear but never the other way around. This is extremely valuable in applications where an input must drive the output but the output must never drive the input. An example of such an application would be in a lift or elevator drive.

Worm gears are also typically much smaller and compact in design than the likes of spur gear configurations. If a worm has a single start, one 360° turn of the worm will advance the worm gear on a single tooth. A 10 tooth worm gear with a single start worm will reduce velocity by a ratio of 10:1, for example. A spur gear, on the other hand, must have at least 12 teeth if it is designed to a high engineering standard and hence would need to be matched with 120 tooth gear to achieve the same 10:1 ratio. It is apparent, therefore, that worm gears can be manufactured into much smaller designs.

Another advantage of the worm gear is its high precision. Coupled with their compact nature their precision means worm gears are often used for tuning musical instruments such as guitars and double basses.

In terms of industrial gearbox applications, worm gears are often found in rolling mills and presses as well as in mining environments and on rudders. Their precision means worm gears are particularly useful in milling heads and rotary tables, used in metalworking. As mentioned, elevators, lifts and escalators often use worm gears due to their compact nature and self-locking abilities.

On the other hand, there are disadvantages to worm gears. Not only are the materials used to manufacture worm gears typically quite expensive, in operation worm gears are prone to excessive heat generation and low efficiencies. This inefficiency often means expensive cooling systems must be used to dissipate the excess heat generated in worm gear operation.

To summarise, worm gears are extremely useful in a number of industrial gearbox applications due to their compactness, smooth operation and self-locking ability. Despite their typically low efficiencies, worm gears are still used across a number of mining and manufacturing industries.

Industrial Inverters

Electric motors and inverters are essential pieces of equipment in a whole host of industry sectors, from construction to food processing and everything in between. Whilst most people have a general appreciation for the requirement of electric motors, far fewer people understand the need for inverters. The fact is however, that any application requiring variable speed demands an inverter. They can also be used to save power in starting and running of an electric motor. From the most basic variable speed applications to complex set-ups involving timers and sensors, inverters are used across dozens of industrial sectors.

With dozens of manufacturers, each producing their own slightly different spec. or brand of inverter, it can be difficult to understand exactly which inverter is right for your company. Here are some factors you might like to consider.

1. Application

Typically, inverters are designed for light, normal or heavy duty. Light duty often includes fan and pump applications, whilst heavy duty could incorporate a number of applications. Selecting the correct inverter for your electrical motor is as simple as matching up the current ratings. If you plan to use the inverter with a number of motors you may wish to consider a dual rated inverter.

2. Manufacturer and Brand

There are dozens of inverter manufacturers both in the UK and globally, each producing similar specifications of inverter. Many manufacturers actually license their inverters to other suppliers to be rebranded and sold under a different name and as such, there is considerable duplication across the market. What this is means is that through careful searching you can find the best value for money inverter without sacrificing quality. Determine exactly what specification you require and compare between like for like models.

3. Warranty, Repairs and Servicing

Consider using a supplier that offers a warranty as repairs can be costly if an inverter fails. In addition, service contracts are useful as regular maintenance will ensure you maximise the inverter’s operational life span and minimise the chance of breakdowns and expensive downtime.

Suppliers often offer advanced thermal imaging detection, otherwise unaffordable to most SMEs, to detect potential sources of failure before they propagate and cause a breakdown. The best service contracts will cover you for all breakdowns, 24 hours a day, 7 days a week.

To summarise, shop around between brands and manufacturers as many inverters are manufactured to similar, if not identical specifications. Consider a dual rated inverter if you wish to use it with different electric motors or simple match up the current ratings of your electric motor and the inverter if not. Finally, when purchasing an inverter, look for warranties along with a service and maintenance contract to minimise the chances of being left out of pocket in the event of an inverter breakdown.


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