MORE TOPICS | Data Centers
Selecting Motors for Data Center Cooling
Keeping data centers as efficient as possible is critical.
Mark Gaskill & Mike Zeller | Nidec/U.S. MOTORS
The booming data center market is bringing new opportunities as well as challenges to pump and motor manufacturers. Zero downtime, energy efficiency and compact size are all factors that data center operators require. Liquid-to-chip cooling loops and ultra-quiet operation are also priorities at data centers.
Keeping servers cool requires high power densities, as much as 120 kilowatts (kW) per server rack in some AI applications. This has increasingly led to the use of liquid cooling applications, as heating, ventilation and air conditioning (HVAC) systems cannot adequately handle these higher power requirements. As a result, pump solutions are becoming increasingly more important to the 24/7 operating environment of a data center.
Manufacturers are responding with new options and technologies, and design engineers continue to consider even more ways to reduce water and energy usage while offering long life and reliability.
One of the biggest areas of impact at data centers is the electric motors and drives that power these technologies, delivering airflow and liquid movement. Motors power not only fans in traditional HVAC equipment but also pumps and compressors that dissipate heat from servers. The latter is proving to be an efficient method for keeping high-density servers cool, but HVAC solutions continue to be used in some instances in data centers.
Motors are responsible for an estimated 40% of a data center’s power consumption, as the cooling equipment runs continually, night and day. Because high efficiency is a priority for data centers, selecting the right motors and drives will position OEMs to help users mitigate risks and cost in terms of downtime and total cost of ownership via efficiency.
Conserving valuable space in the data center footprint is also a top need, and some motor manufacturers are supporting this trend with higher power and smaller frame sizes. In addition, redundant or backup motors are common for critical equipment and are highly recommended for data centers.
This article provides an overview of the critical role motors play in data centers, the importance of reliability and the importance of smaller, high-power-density motors in data center cooling applications.
The Efficiency Game
Considering that a single ChatGPT query consumes nearly 10 times as much electricity as a non-AI Google search query, the stakes are high in terms of the need for data centers to operate as efficiently as possible.
The need for high-efficiency motors has increasingly led to the use of variable speed motors. Utilizing variable speed on variable torque systems such as fans and pumps allows the equipment to match the cooling needs, saving up to 40%-60% in energy costs compared to fixed-speed systems.
Synchronous motors are often a preferred choice and include multiple technologies such as synchronous reluctance, synchronous reluctance with permanent magnet assistance and brushless permanent magnet motors. When a synchronous motor is integrated with a variable frequency drive (VFD), the industry refers to those as electronically commutated motors (ECMs). Synchronous motors can also be paired with separate VFDs.
| IMAGE 1: In CDUs, high-efficiency motors and pumps circulate the fluid to prevent computer servers from overheating. (Image courtesy of Nidec/U.S. MOTORS)
Primary Loop Pumps
Because water conducts heat approximately 25 times more efficiently than air, liquid cooling is a good option for keeping servers cool in data centers. Liquid cooling also allows for greater than 100 kW individual rack densities, which is essential in meeting ever-increasing AI requirements.
Data centers require the use of large pumping units to move water throughout the facility. This is considered the primary loop, which supplies water to coolant distribution units (CDUs) to cool the secondary cooling loop.
Commonly, National Electrical Manufacturers Association (NEMA) premium efficiency induction motors with a VFD are utilized to save energy over fixed speed. The momentum in the industry is to take the next step to variable speed synchronous motors. In addition to saving energy, they are often smaller and lower weight and run cooler.
Coolant Distribution Units
CDUs are used in data centers to manage the circulation, filtration and temperature of coolants for servers and processors. CDUs provide controlled coolant for heat exchangers, direct-to-chip and immersion cooling devices.
The equipment prevents server overheating and supports high-density, space-saving racks. CDUs also ensure that the primary facility water remains separated from the secondary loop directly cooling the servers, allowing for precise, targeted cooling.
A typical CDU commonly cools up to approximately 2 megawatts (MW) of processing power while consuming approximately 100 kW to provide circulation of coolants at full load. Matching demand of the process heat is the goal and the reason efficiency is a high priority. Two different motor types are currently used on CDUs—synchronous and induction motors. To maximize efficiency at partial loads, synchronous motor usage is growing quickly to reduce power consumption.
Synchronous motors have zero slip and are therefore synchronized with the frequency of the power supply, and the rotor has essentially zero losses. Most synchronous motors are rated as NEMA Premium 4 or higher efficiency and will consume less energy at the same power output as induction motors. At partial loads, the advantages of synchronous motors can expand to as many as 15 points of efficiency. These higher-efficiency motors are more complex than asynchronous motors, typically, and may cost more as a result.
VFDs enable the motor variable speed operation to match system demand and can be integrated (ECM) or stand alone. They can offer precise cooling control, helping to prevent hotspots that could impact server performance. Operating at variable speed can also extend motor, fan and pump life due to less wear and tear over time.
Fire Pumps
Data centers, like all facilities, require critical fire protection. Horizontal and vertical fire pumps deliver dependable, high-efficiency water movement, ensuring compliance with safety standards while safeguarding facility infrastructure.
Fire pump motors utilize induction motors, which are a straightforward design that has a simple on/off switch that is activated when needed. No variable drive motors are required. However, the use of VFDs is becoming more common to limit water hammer (a sudden start or stop in water flow) and control the system.
The High Cost of Downtime
Equipment downtime presents a considerable challenge at data centers. Various reports show that the average cost of data center downtime is $9,000 per minute, a staggering figure that illustrates why reliability of equipment is a high priority. Redundant systems are common for critical equipment, and data center cooling certainly fits the bill. Uninterrupted pump and motor operation is mandatory for cooling, so cooling systems rely on N+1 Redundancy (one active, one standby) pump and motor setups. Predictive maintenance schedules are also highly recommended to extend motor and pump life and keep them operating efficiently.
Selecting reliable, high-efficiency motors and drives will help data center facilities keep energy costs down and reduce equipment downtime.
Mark Gaskill is senior market manager at Nidec/U.S. MOTORS.
Mike Zeller is market manager, commercial flow at Nidec/U.S. MOTORS. For more information, visit acim.nidec.com/en/motors/usmotors.
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