Large axial fans are high inertia loads, which means that motor start times are increased. With a standard motor this could lead to overheating. Therefore the motors have to be specially designed to withstand the increased temperature rise during start and stall conditions, and have stall times longer than their start times.
“Our new high inertia motors are based on our well-established modular induction motor, so customers can be confident they are getting robust, reliable motors. We adapted the platform by optimizing the rotor bar composition, dimensioning and overall design for high inertia loads,” explains Ms. Karita Forss of ABB’s high voltage induction motor product management.
“The rotor bars are made from carefully selected materials, including higher resistivity copper alloys. The motors have been re-dimensioned to accommodate the temperature rise associated with high inertia starts, and the overall design has been optimized to achieve the optimum balance between torque and temperature performance with high inertia loads.”
All of ABB’s high inertia motors for axial fan applications have stall times longer than their start times in normal operating conditions, which means that relay safety protection can be arranged safely. The 6 - 10 pole motors are designed in accordance with NEMA standards. They cover the power range 7000 -18500 HP in frame sizes 710 – 900, and can be supplied up to 13.2 kV 60 Hz. WPII, TEWAC and TEAAC cooling systems are available. The applied inertia level is three times the published NEMA MG-1 chart and the service factor (SF) is 1.15, with a class F temperature rise.
Depending on their application, customers have a choice between motors that meet higher and lower stall requirements. Motors meeting higher stall requirements have a ‘hot’ stall time at least five seconds longer than the start time at all voltage levels from 80% to 100% of nominal. Motors meeting lower stall requirements have a ‘cold’ stall time that exceeds the start time at all voltage levels over the range 80% - 100% of nominal.
ABB (www.abb.com) is a leader in power and automation technologies that enable utility and industry customers to improve their performance while lowering environmental impact. The ABB Group of companies operates in around 100 countries and employs about 145,000 people.
For help with any technical terms in this release, please go to: www.abb.com/glossary.