Single-phase motors are typically used on farms, office buildings and residential applications where low output power is required and no three phase system is available. However, with the ongoing improvements in technology and lowered cost of smaller variable speed drives (VSDs), three-phase motors can now be used in these applications.
“Single-phase motors have a single winding and are fed with a single-phase voltage. There are various arrangements that can be used but the most common design is the one that uses a starting capacitor or a starting and a run capacitor, both equipped with a centrifugal and a stationary switch,” explains Edson Cristofolini, product and projects manager at Zest WEG Group.
Three-phase motors, on the other hand, have three windings and are fed with a three-phase voltage. The interaction between the magnetic field on the stator and the induced magnetic field on the rotor makes the motor run.
“When using a single-phase VSD you would still have a single-phase feed to the drive allowing the existing installation to be used without any modification, however there would be a three-phase voltage feed to the motor,” continues Cristofolini. “This is possible because the VSD will rectify the single-phase voltage from its input and switch the voltage on and off with IGBTs, from a DC link provided by a capacitor bank, to create the three-phase signal on the output to feed the motor.”
In general, three-phase motors present a better efficiency and power factor than a single-phase motor and they are also more reliable, lighter and require less maintenance, as no capacitor or internal switches are needed.
“Added to the performance and reliability of three-phase motors, when they are run on a VSD it eliminates the need for a direct online starter with contactors and thermal relays, since all the protection is now built in the VSD,” says Cristofolini.
WEG manufactures a variety of VSDs which also provide additional features not available on a normal starter for single-phase motors. These include current and speed reading, under voltage and phase protection, fault history and speed variation, which contributes to power savings.
“The VSD also incorporates analog inputs and outputs as standard and allows communication with a PLC or scada system,” adds Cristofolini.
“Whilst cost comparisons, between a single- and a three-phase motor typically focus on the cost of the motor, one also needs to take the cost of the starters into account. A comparison undertaken by Zest WEG Group indicated that in most of the cases, based on current market prices, it is more cost effective to use a three-phase motor with a VSD than to use a single-phase motor with a starter. In addition, there is a higher off the shelf availability of three-phase motors and VSDs,” points out Cristofolini.
“It is important to remember that the VSD has on-board electronics, thus requiring additional care in use. In spite of this fact, VSDs are becoming increasingly more user friendly and require little maintenance. This makes them the perfect cost effective alternative to a single-phase motor with starters,” he concludes.
Food industry operations – not as simple as flipping a switch Schneider Electric South Africa
Electrical Power & Protection
The food industry represents a huge portion of the global economy, and is expected to reach $9,68 trillion in 2025. It is completely reliant on power, and due to its sheer size and the nature of its operations, power interruption can be catastrophic for its bottom line.
Read more...Waste To Energy thermal technologies DirectLogic Automation
Electrical Power & Protection
The vast quantities of waste produced around the world are a large and growing problem. Waste to Energy technology based on pyrolysis is a solution.
Read more...New enhanced Breaker Status and Communication Module Schneider Electric South Africa
Electrical Power & Protection
Schneider Electric has launched its new Breaker Status and Communication Module (BSCM) Modbus SL/ULP, which delivers enhanced performance, improved connectivity and simplified integration for power distribution systems.
Read more...Building green industries to scale green economies
Electrical Power & Protection
Africa is taking bold steps to build green industries across the continent. Namibia is a trailblazer in the hydrogen space, with up to five Final Investment Decisions scheduled to be made in 2025/2026 and is pioneering a world first for green industrialisation.
Read more...Easing the path for IPPs navigating South Africa’s energy regulations
Electrical Power & Protection
Independent Power Producers and developers venturing into South Africa’s renewable energy sector face a challenging regulatory landscape. SPS is a renewable energy asset management company that is actively expanding into the energy trading and wheeling market, which will enable businesses to buy and sell energy directly
Read more...How energy storage will make or break SA’s renewable transition
Electrical Power & Protection
Energy storage is no longer an add-on, but the foundation of a reliable, resilient and renewable energy system. As South Africa accelerates towards a greener future, storage innovation could determine the difference between progress and paralysis.
Read more...Condition-based maintenance can revolutionise business continuity Schneider Electric South Africa
Electrical Power & Protection
As businesses experience growing pressure to enhance operational efficiency and reduce downtime due to electrical failure, condition-based maintenance becomes essential for preventing unforeseen equipment breakdowns by assessing the real-time health of electrical systems.
Read more...Boiler selection for optimal thermal energy performance
Electrical Power & Protection
The changing world of boilers means companies wishing to improve their thermal energy efficiencies while containing costs and environmental impacts must make careful and informed decisions. AES’s rich pool of experience, ability to keep pace with new steam trends and technologies, and understanding of their clients’ production processes can assist clients to weigh up different options in a careful and informed manner.
Read more...Securing Africa’s energy future starts at home ACTOM Electrical Machines
Electrical Power & Protection
Africa’s energy demands are surging, but the current reliance on imported solar technology leaves the continent vulnerable. This is why the prospect of building inverters and lithium batteries locally, designed for South Africa’s specific needs, is so promising.
Read more...Dry-type transformers for Dutch intake substation
Electrical Power & Protection
A data centre in the Netherlands is the site of a recent innovation on the transformer landscape, where TMC Transformers has designed, manufactured and installed dry-type transformers in a large intake substation.
printer friendly version