ABB has developed its most powerful low-voltage motor to date – a water-cooled machine in a compact 500 frame size, that can deliver up to 2MW. The M3LP 500 motor weighs about 1,000kg less than machines with comparable ratings, thanks to its use of a cast-aluminium rotor instead of the more common welded copper bar construction.
The machine is based on a four-pole design originally developed specifically for marine and offshore applications, where compact dimensions and a low weight are often essential. ABB has now decided to widen the target market to industrial applications and added six- and eight-pole versions spanning ratings from 800–2,000kW. All of the motors below 1MW have IE3 efficiency ratings (IE ratings have yet to be drawn up for larger machines).
The 690V, 50/60Hz motors can either operate direct-on-line or be driven by an inverter – in which case they can be operated close to zero speed. The 2.2m-long machines weigh 5,200–6,000kg and are capable of speeds up to 1,800 rpm (in a four-pole version). They use standard terminal boxes up to 1.2kA and are available in foot or flange mounting, or a combination.
ABB sees the new motor as a strategic product that will become a flagship range. It says that the range offers higher power densities, lower noise levels and a lower operating temperatures than rival machines. The motors have a class B temperature rise compared to class F for most competitors.
“We’re proud to rank number one on several important motor qualities,” says Marcus Westerlund, ABB’s product manager for LV water-cooled motors.
Since the marine version was launched in 2016, ABB has found there is interest from other sectors. “Water-cooled motors are clearly on the increase,” Westerlund reports. “This past year, we’ve seen a growing interest from such diverse industries as mining, minerals, water and wastewater, and manufacturing. Word spreads fast and we believe the M3LP 500 will prove a great success in many applications.”
Water-cooled motors have high power-to-weight ratios. Because water is a more effective cooling medium than air, their operating temperatures can be relatively low, and more power can be extracted from them.
A smaller water-cooled motor can provide at least as much output power as a larger conventional air-cooled motor, freeing up space for other uses – or allowing more power to be delivered in the same space.
Another advantage is that water-cooled motors don’t need external ventilation, avoiding the cost of ventilation systems, saving more space and reducing noise levels further. And with no ventilation, a water-cooled motor can be sealed tightly, preventing contaminants from entering its interior. The IP55-protected machines can be used in damp, dirty locations that would be unsuitable for air-cooled motors.
The motors have a corrosion-protected steel frame rather than traditional cast-iron. There are no external cooling ribs, which tend to collect dirt on air-cooled motors.
According to Westerlund, developing and manufacturing the cast-aluminium rotors for the new motors posed “a lot of challenges”. The casting, which ABB does in-house, is “a really delicate process” and has required manufacturing machinery to be redesigned and rebuilt. “We’re going to the limits of what we can do,” says Westerlund.
Another novel aspect of the motors’ design is the use of random winding for the stator coils, rather than the standard form-wound approach. The motors’ bearings are cooled at both ends, for longer service lives.
The new motors are being built in Finland. Lead times are currently about 25 weeks.