14 october 2016: Continuity is an important topic for Piet Brouwer Electrotechnology’s worldwide clientele. The accelerating growth of the global population is bringing new challenges to the issue of energy supply. This is why emergency power systems are increasingly likely to use so-called UPS (Uninterruptible Power Supply) systems, which ensure continuous and clean power. UPS systems come in all shapes and sizes, with the most suitable type depending on the relevant application. This article examines which applications are most common in practice and the difference between dynamic and static UPS systems.
Controlled shutdown & ride-through
In case of a power failure at the power utility, the UPS units can react in two different ways. In a ‘controlled shutdown’ application, they will provide enough energy to allow the production line to stop working in an orderly manner so that specific production processes can be stopped safely and/or start again unhindered when power comes back. In the case of a ‘ride-through’ application, the UPS instead bridges the required power during a failure until the emergency power supply can come online. This allows the production process to continue uninterrupted 24 hours a day. The two applications hinge on two different types of UPS systems: dynamic or static.
Dynamic and static UPS systems
A dynamic UPS uses a flywheel to store energy. This flywheel is placed in a vacuum housing which minimises friction and the amount of power required to keep the wheel at constant speed. Unlike a static UPS, the efficiency of a dynamic UPS is dependent on the quality of the power utility network. During normal operation, the dynamic UPS has an efficiency of 97%.
A static UPS, by contrast, uses batteries for energy storage. Many different kinds of batteries can be applied, with the most common being the types that require little to no maintenance, such as nickel-cadmium (NiCd), lead-acid (VRLA) and lithium-ion (Li-ion) batteries. The advantage of the latter is their high energy density and high discharge currents for each cell, allowing the whole system to be compact in size. Moreover, developments pioneered in the automotive industry mean that the cost of this type of battery continues to fall.
Static UPS systems used to be less efficient because the double conversion – of alternate current from the mains to direct current for the batteries & inverter, and of direct current from the batteries to alternate current for the consumer – led to significant cumulative losses and low efficiency (85-92%). Now that the underlying technology has been perfected, the efficiency has increased to a total of 96% for the entire system. The double conversion means that the UPS produces a pure sine wave output.
Filtering
The lifespan of electronic devices is affected by problems in the voltage of the electricity which powers them. Both UPS systems filter these problems, creating a pure sine wave output for consumers. This ensures longer life for the connected devices and reduces the power losses in cables caused by these problems. Filtering these problems requires substantial power on the part of the UPS system and it is possible to connect the UPS to the emergency power to allow a quick response to any resultant capacity loss.
Advice
Piet Brouwer Electrotechnology has experience in the UPS market and the company’s independence of any brands allows it to choose the best solution and finished product for every application. If you feel you can no longer see a way through the maze, Piet Brouwer Electrotechnology can help you figure things out.
Piet Brouwer designs and installs UPS system in a brewery in Congo
A Congolese brewery was experiencing interruptions in the production process due to power outages. Each disruption led to the production line having to be rebooted, causing considerable losses in output. Piet Brouwer Electrotechnology designed and installed a suitable solution to this problem: a dynamic UPS system, which provides a clean supply voltage, was fitted at each production line, leading to far fewer malfunctions and less damage to equipment. These systems also ensure that the main consumers are guaranteed at least 25 seconds of electricity supply after the power fails, so that the most urgent processes can continue uninterrupted while the emergency generators come online and can take over.
For this solution, Piet Brouwer Electrotechnology equipped its existing electrical power plant with a new, fully automatic synchronisation and load sharing system, in which four 1500 kVA diesel generator sets start supplying the brewery with power within 13 seconds. Once the mains network is stable again, the system can switch back without interruption. The investment had a payback period of just two years at this factory.