Monthly Archives: November 2021

New Battery Technology for UPS

Most people know of the Lithium-ion battery technology in use mainly due to their overwhelming presence in mobile sets. Those who use uninterruptible power supplies for backing up their systems are familiar with the lead-acid cells and the newer lithium-ion cells. Another alternative technology is also coming up mainly for mission-critical facilities such as for data centers. This is the Nickel-Zinc technology, and it has better trade-offs to offer.

But the Nickel-Zinc battery technology is not new. In fact, Thomas Edison had patented it about 120 years ago. In its current avatar, the Nickel-Zinc battery offers superior performance when used in UPS backup systems. They offer better power density, are more reliable, safe, and are highly sustainable.

For instance, higher power density translates into smaller weight and size. This is the major difference between a battery providing energy and a battery providing power. In a data center, the UPS must discharge fast for a short period for maintaining operational continuity. This is what happens during brief outages, or until the backup generators spin up to take over the load. This is the most basic power battery operation, where the battery must deliver a high rate of discharge, and it does so with a small footprint.

On the other hand, Lead-acid and Lithium-ion technologies offer energy batteries. Their design allows them to discharge energy at a lower rate for longer periods. Electric vehicles utilize this feature, and the automotive industry is spending top dollars for increasing the energy density of such EV batteries so that the user can get more mileage or range from their vehicles. This is not very useful for data center backup, as the battery must have a higher energy storage footprint for supporting short duration high power output requirements.

This is where the Nickel-Zinc battery technology comes in. With an energy density nearly twice that of a Lead-acid battery, Nickel-Zinc batteries take up only half the space. Not only is the footprint reduced by half, but the weight also reduces by half for the same power output. As compared to Lithium-ion batteries, Nickel-Zinc batteries not only excel in footprint reduction, but they charge at a faster rate while retaining thermal stability. This feature makes them so useful for mission-critical facility uptime.

Nickel-Zinc batteries have proven their reliability as well. They have clocked over tens of millions of operating hours for providing uninterrupted backup power in mission-critical applications. Another feature very useful for data center operations is the battery string operations of the Nickel-Zinc technology.

When a Lithium-ion or a Lead-acid battery fails, the battery acts as an open circuit, preventing other batteries in the string from transferring power. On the other hand, a weal or a failed Nickel-Zinc cell remains conductive, allowing the rest of the string to continue operations, with a lower voltage. In emergency situations, this feature of the Nickel-Zinc battery is extremely helpful, as the faulty battery replacement can proceed with no operational impact and at a low cost.

In parallel operation also, Nickel-Zinc batteries are more tolerant of string imbalances, thereby maintaining constant power output at significantly lower states of health and charge as compared to batteries of other technologies.

Power Transmission Through Lasers

Wireless power transfer has considerable advantages. The absence of transmission towers, overhead cables, and underground cables is the foremost among them, not to exclude the expenses saved in their installation, upkeep, and maintenance. However, one of the major hurdles to wireless power transmission is the range it can cover. But now, Ericsson and PowerLight Technologies have provided a new proof of concept project that uses a laser beam to transmit power optically to a portable 5G base station.

Wireless power transmission is not a new subject to many. People use wireless power for charging many devices like earbuds, watches, and phones. But the range in these chargers is short, as the user must place the device on the pad of the charger. This limits the usefulness of the wireless charging station for transmitting power. Although labs have been experimenting with larger setups that can charge devices placed anywhere within a room, reports of beaming electricity outdoors and for long distances have been rather scarce.

PowerLight has been experimenting with wireless power transfer for quite some time now, and they have partnered with Ericsson, a telecommunications company, for a proof of concept demonstration. Their system consists of two components, a laser transmitter, and a receiver. The distance between the transmitter and receiver can vary from a few hundred meters to a few thousand meters.

However, unlike a Tesla coil, the PowerLight device does not transmit electricity directly. Instead, at the transmitter end, electricity powers a powerful laser beam, sending it directly to the receiver. In turn, the receiver uses specialized photocell arrays to convert the incoming laser back into electricity for powering connected devices.

Such a powerful laser-blasting through the open air can be a dangerous thing. Therefore, PowerLight has added many safeguards. They surround the beam with wide cylinders of sensors that can detect anything approaching. The sensors can shut off the beam within a millisecond, if necessary. In fact, the safety system is so fast that a flock of birds is not affected when flying through the laser beam, but there is an interruption at the receiver.  To overcome such fleeting interruptions, and cover longer-term disruptions as well, the PowerLight system has a battery back-up at the receiver end.

PowerLight is using their system to power a 5G radio base station from Ericsson, that has no other power source connected to it. The base station received 480 watts from the transmitter placed at a distance of 300 m. However, according to the PowerLight team, the technology can send 1000 watts over a distance of over 1 km. They also claim there is room for future expansions.

Wirelessly powering these 5G units could make them more versatile, as they will then become portable, and capable of operating in temporary locations. This will also allow them to operate in disaster areas, where there has been a disruption of infrastructure.

According to PowerLight, their optical power beaming technology may be useful in several other applications also, such as for charging electric vehicles, in future space missions, and in adjusting the power grid operations on the fly.

TI Driver for BLDC Motors

When simple motors were more frequently used, it was relatively easy to design products with them. Controlling such motors was simple, whether it was a brushed DC motor or a single-phase AC motor. There was no need for sophisticated hardware or software for designing a product with a motor.

However, sophisticated BLDC or brush-less DC motors are replacing most of the above motors because of several advantages like quiet operation and high efficiency. But these advantages come at the cost of design knowledge and effort, requiring both hardware and software development. Texas Instruments has developed a new integrated circuit that allows designers to achieve all the benefits easily from these motors.

The biggest benefit offered by BLDC motors over older designs is their improved power efficiency. Most government regulators today demand that electrical products meet strict efficiency standards. In most cases, meeting these requirements is possible only through the use of BLDC motors.

Motors are mechanical devices and therefore, they make noise when operating. Although the quiet operation is not usually a design goal for most products, using a BLDC motor offers a way to achieve low noise operation.

There are further advantages to using BLDC motors. One of them is low voltage operation, and the other is a longer life. Manufacturers of BLDC motors are now offering them in larger sizes for use in bigger products.

As stated earlier, BLDC motors are now replacing brushed DC motors and in some cases, AC motors as well. Some practical examples are robotic vacuum cleaners, pumps, fans, washing machines, humidifiers, and air purifiers. They are useful for multiple automotive devices as well.

Functionally, a BLDC motor works under the same principles that govern the operation of all motors—rotation is from the interaction of two magnetic fields, one fixed and the other movable. Frequently, the BLDC motor will have multiple stator coils embedded in the periphery of the motor assembly. With the stator coil wired into three groups, it performs as a three-phase motor does. The rotor on the BLDC motor consists of several permanent magnets rotating in the circle formed by the stator coils. The user only has to apply a sequence of pulses to the stator coils.

The timing of the pulses must match their interaction with the permanent magnets. The control circuitry that drives the stator coils gets the correct timing from multiple sensors indicating the orientation of the rotor. These sensors are mostly Hall-effect devices that produce signals that the controller requires for moving the magnetic fields on the stator coil.

There are numerous variations of the approach to control the BLDC motor. One of them is a sensor-less method using the back electromotive force the rotating rotor magnets induce into the stator coils. The sensor-less method typically reads the feedback voltages in the motor stator winding and processes them into control signals.

Many motor controllers are pre-programmed and packaged BLDC motor control modules. This is usually satisfactory for common applications. Others, however, require a custom design. The MCF8316A from TI is a single chip BLDC motor controller chip that only requires inputs for speed, direction, and torque. The IC takes care of the rest.