Delivering IE4 savings for a Zone 1 application

Improving the energy efficiency ratings of electric motors is a worldwide goal. However, exemptions in the regulations mean that for applications in potentially explosive atmospheres there is no obligation to implement the latest technology. Despite this, for one oleochemical processing company improving energy efficiency is an important objective. This led the company to consider the possible options when a number of its existing ATEX motors needed to be replaced.

The manufacturing processes involved in the production of oleochemicals often involve potentially explosive atmospheres which require specialist equipment to ensure safe operation. In this particular application a number of mixing vessels were located in a Zone 1 atmosphere and powered by explosion-proof gear motors. The company wanted to replace the outdated gear motors with new equipment of a similar specification but with improved energy efficiency and the ability to operate via inverter control.

Application engineers at Bauer assessed the application requirements and were able to design a drivetrain that consisted of an inverter duty IE4, ATEX rated permanent magnet synchronous motor (PMSM), coupled to a BG70 gearbox and controlled via a Danfoss FC-302 inverter. This combination provided the necessary control while offering the energy efficiencies required by the company and also meeting the necessary safety levels.

Energy efficiency is a key determining factor for many companies today when specifying new geared motor solutions. For this reason Bauer Gear Motor has developed the new motor range in anticipation of the new IE4 classification and to offer greater energy efficiency.

“It is well known that electrical motors use 65% of the energy used in industry, but a lesser known fact is that 96% of the lifetime costs of an electric motor is associated with the energy consumption. This shows the importance of the overall efficiency compared to the initial purchase cost in the terms of the total cost of ownership (TCO),” said Markus Kutny, product manager, Energy Efficiency Solutions at Bauer Gear Motor. “The design of modern drivetrains requires specialist knowledge and expertise in order to produce a product which will deliver efficiency, smoothness and low noise qualities as well as excellent reliability. However, further benefits of a good design can be gained by ensuring the drivetrain is properly integrated into the application.”

The original asynchronous motors (ASM) installed in the oleo chemical process were designated as Ex d (explosion proof) and suitable for operation in Zone 1. Bauer engineers concluded that the new equipment could be rated to Ex e (increased safety) while still meeting the necessary requirements of Zone 1 operation.

The design and manufacture of explosion-proof motors often results in the overall size and weight of the motor increasing. However, Bauer’s design and engineering has incorporated energy saving technology as well as the additional requisite protection while minimising the overall footprint of the motor. Comparing frame sizes of similarly rated IE3 ASMs to Bauer’s PMSMs up to the 11 kW model shows that the Bauer models are either equal to, or one frame size smaller than, the equivalent ASM. This optimises the integration possibilities for this range of motors as well as assuring increased power and torque compared to a motor of the same frame size.

The proposed solution for the oleo chemical application was based around the PMSM series, which is an environmentally-friendly range of motors, employing a highly efficient rotor design that integrates embedded permanent magnets made from rare-earth metals, in place of a squirrel-cage rotor found in most low voltage induction motors.

The design of the PMSM is said to offer a number of benefits. For example, it reduces heat losses from the rotor by 100%, total losses by approximately 25%, and increases total efficiency by 10% or more compared to the most efficient conventional motors. For the end user, this translates into lower total cost of ownership, a reduction in CO2 emissions and on-going savings to help buffer against the effects of future increases in energy costs. 

The PMSM was coupled to the BG series of helical geared motors which offer torque values of up to 18,500 Nm with high output speeds. The motors can also be integrated with an inverter to ensure that the required speeds at each stage of the mixing process are maintained.

In many cases, manufacturers of specialist motors such as these specify a particular inverter that has to be installed as part of the application. Bauer does not place any such restrictions on an application, preferring to allow the client to use an inverter that best suits the situation. This ensures that maintenance managers can optimise their spares inventory as well as avoiding the need for additional technical training on a new inverter.

This application shows that, for those involved in the chemical processing industry, it is no longer necessary to compromise on energy efficiency due to the application requiring ATEX certified equipment.