Explanation mechanisms AC permanent magnet

Explanation mechanisms AC permanent magnet

This article is written as a practical guide on the mechanisms of AC synchronous permanent magnet (ASRM), which replace the traditional device of alternating and direct current in the lift building industry. The bulk of the article is based on a report by the company’s representatives Kinetek, made at the International Exhibition of elevators and escalators in 2010, which took place on 3-5 February in Mumbai.

Looking Back

If you recall the days around 1900, then the workhorses of the industry were huge Lift mechanisms DC. Mechanisms DC produced in geared and gearless version. Their lack of -large size and relative complexity — a negative impact on the management and maintenance. Around 1930 began the widespread use of single-speed AC mechanisms for small passenger lifts. These mechanisms are smaller, less complexity, longevity and ease of maintenance. The engine-generator sets, appeared on the market in the area in 1940, provided the load capacity at the level of the mechanisms of direct current, without having their shortcomings in terms of management.

Engines hoists DC got a second wind with the advent of silicon SCR in the 70s of the last century. Drives on silicon SCR provided excellent control of DC motors without requiring a generator. They even allowed to upgrade the engine-generator sets by simply removing the generator from the scheme. However, drives on silicon SCR were affected by noise and difficulty approaching the pure sine wave. In the 1990s considerable progress in the development of AC inverter drives, allowing greater use of engines and mechanisms of the AC by the extended load range and smooth control on a wide range of speeds. However, the heavy cockpit and high speed continues to provide a market for DC arrangements.

Mechanisms of AC permanent magnet (ASRM) appeared around 1995 to the present time are often considered the best choice for most elevator systems. Mechanisms ASRM smaller in size and weight than the DC mechanisms provide a smooth change in power over a wide range, is extremely durable and easy to maintain. They are about 35% more efficient in terms of energy consumption compared with AC asynchronous mechanisms.

Technology ASRM

In mechanisms ASRM offline gear (which is necessary when using the AC induction motor for lifting heavy loads), respectively, have inherent vibration, noise, performance and small leakage of lubricant. Gearless ASRM mechanisms allow to move heavier loads at higher speeds — up to 7 m / s at the ratio 1: 1 and up to 3.5 m / s at a ratio of 2: 1. ASRM mechanisms provide a higher starting torque without the need for the gearbox. Compatibility

Drives most of the major manufacturers can work with the mechanisms of ASRM. More advanced drives can «explore» the characteristics of a mechanism to establish the critical parameters, without requiring user input. This learning process is designed to ensure the best performance drive / mechanism. One example of a product using this technology — a new integrated management system of the company Fusion ™ Kinetek, which combines in a single device, and lift the drive control logic. This device has the training and empowerment for systems ASRM, in respect of asynchronous AC motors.


Permanent magnets, on which the technology ASRM are rare earth magnets from iron oxide, bromine and metal oxides such as hematite and magnetite. These materials are crushed into a fine powder, making powder slurry is formed at very high pressure, heated, sintered, grinded, polished and finally magnetized. Magnets made from these materials are known as «ceramic» magnets may be ferrite, neodymium, niobium plastics etc.

Ceramic permanent magnets are not electrically conductive, cost-effective and can be easily and quickly get it, and they can create extremely powerful permanent magnetic field. These magnets are used in DC motors, brushless DC motors, synchronous motors, water pumps, loudspeaker, couplings, water meter and traditional magnetic coupling.

The magnets used in the mechanism AC permanent magnet Lift

The gearless synchronous mechanism AC installed in elevators, used ceramic magnets of neodymium. These magnets are made from a combination of neodymium, iron and boron; they appeared in the late 1970s. Among the characteristics of neodymium magnets — good power relative to their size, the ability to lift a load that exceeds their own weight in 1300 again, and relatively high production costs (offset by ease of use and power). The magnetization of neodymium magnets is constant and does not weaken over time.


AC motors to permanent magnet passed operational tests to lift building industry. They first appeared in the series EcoSpaceTM KONE’s in 1992, and then use them in systems Gen2® company Otis, and now in a series of Kinetek, ASRM engines have proven to be an extremely durable, reliable and energy-saving devices. It is important that the mechanisms ASRM provide a high quality of motion in a wide range of acceleration, velocity, and contractual requirements on the load.

About Kinetek

Company Kinetek — private American manufacturer, which employs more than 2 500 people, including more than 300 graduate engineers at 28 enterprises around the world. Among 13 design centers, it provides a wide range of technologies and product characteristics. Kinetek company serves global markets, supplying engines, gear assembly, drives, controllers, modular kits controller boards, emergency power supplies to ensure uninterrupted power supply, and more.

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