Choosing a speed controller for your electric motor

Photo: Courtesy of eMotors

A speed control enables the motor to achieve maximum efficiency during all phases of operation. Avoiding wear and tear on the motor, electrical infrastructure, driven load during acceleration/deceleration, and precisely maintaining the correct speed for the application at all times. This means that you can enjoy a full service-life from your motor and all the electrical/mechanical components connected to it, as well as substantial power savings, while maintaining peak productivity.

To reap all the benefits that an electric motor drive can offer, it is important to choose one that is a perfect match for your application. By taking the time to assess your individual needs, and partnering with a vendor like KB Electronics who offer a diverse, affordable and customizable range of electric motor drives and accessories, you can achieve cost-effective optimization of your business with hassle-free installation and operation.

The first step when choosing a drive for your electric motor is to make sure it matches the type of motor you have. Different motors often require different speed control methods – for example, the speed of an AC motor is determined by the frequency of the AC power supply, whereas DC motors are controlled by varying the voltage of the DC supply. KB Electronics can supply you with electric motor drive solutions for a range of both AC and DC applications, as well as custom controllers for OEM applications involving brushless DC, PMSM, PSC and shaded-pole motors.

Second, check that the motor drive is designed to handle the power required by your motor under maximum load. Utilizing a drive that is capable of delivering what your motor needs in all circumstances without experiencing excessive stress will result in considerable savings in maintenance and parts replacement costs. To cover all your needs, KB Electronics offers several line-ups of speed controllers for AC motors up to 30 hp, and for DC motors up to 5 hp.

Especially with high-powered motors driving high-inertia loads, it is important to soft-start the motor by gradually increasing torque, preventing harmful current spikes in the motor and electrical system as well as mechanical shock to the driven load. Also, sufficient breakaway torque is required at the start to overcome the inertia of a heavy load. With a user-selectable starting time of 0.5 – 4 seconds, and 200% of rated torque available at the start to get heavy loads moving, KB’s drives can smoothly handle any start-up situation while simultaneously limiting inrush current and protecting the motor from heat and stress caused by current spikes.

Once the motor is rotating, an electric motor drive must be able to precisely manage the speed of the motor over the full speed range and through variations in the load. While DC motors generally provide consistent torque over the entire speed range, AC motors suffer from loss of torque at lower speeds, as well as a phenomenon known as ‘slip’ where the rotor rotates slower than the supply frequency as the load increases. Without a speed controller that is capable of compensating for this, it will not be possible to maintain consistent speed with varying load. By utilizing Sensorless Flux Vector Compensation technology with Static Auto-Tune, KB’s highly capable drives can provide precise speed control from zero to full load over a wide frequency range.

When it is time for a motor to stop, it is often desirable to apply braking to quickly and smoothly bring the driven load to a halt. Additionally, when power stops being applied to a motor that continues to spin because of the momentum of a heavy load (a situation known as an ‘overhauling load’), the motor begins to act as a generator, and this can lead to potentially damaging voltage spikes in the electrical system. Dynamic braking is a method that is used to solve both problems by dissipating the power produced by an overhauling load as heat, simultaneously creating an electro-mechanical braking effect on the motor. To make it easy to benefit from dynamic braking, KB offers a simple-to-install Dynamic Braking Module (DBM) for selected drives that achieves a considerable 25% dynamic braking torque and 200% instantaneous braking torque to quickly and safely bring the load to a stop.

Ensure that an electric motor drive can be operated from the power supply you have available. AC motor drives must be able to receive the voltage and frequency provided by the AC power supply and convert it to the full frequency range required by the motor. Also, if your power supply is single-phase, a drive must be able to convert it to the three-phase power required by an induction motor. To provide flexible options for different power supply characteristics, KB Electronics offers various 1-phase input/3-phase output solutions for AC drives, as well as DC solutions with 1-phase AC input, for input voltages ranging from 115VAC to 460VAC.

For off-the-grid battery-driven solutions, it is necessary to utilise a DC-to-DC drive, and KB has you covered with a range of options for 12V, 24V, 36V and 48V applications.

An electric motor drive is often part of a sophisticated and highly automated control system, and when this is the case it is critical to choose a product that has the capability to not just run its own software but also integrate easily with existing and future infrastructure. Interfacing capability is paramount, and to provide outstanding flexibility, KB Electronics offers a variety of drives with an ‘SI’ interface port which allows them to plug into many common fieldbuses, seamlessly integrating into your current system. Many of KB’s options also come with an integrated PLC, enabling you to program your own control software, as well as a range of I/O connections for building your own control loops, giving you the ability to build your control system the way you want it to be.

An electric motor drive solution that can be customized for your specific application will also provide you with the ability to optimize and troubleshoot your operation with user-friendly tools and network integration. KBConnect is a PC software tool from KB Electronics designed to aid productivity when commissioning, optimizing and monitoring drive and system performance, giving operators access to the information they need to quickly achieve peak performance of the speed controller and maintain it at all times. To achieve next-generation network connectivity, KB also provides controllers that are capable of remote diagnostics with optional industrial Ethernet and fieldbus communication, enabling off-site monitoring and troubleshooting of the application.

Especially for industrial applications, it is necessary to choose a speed controller that can handle the physical environment that it will be operating in. If the speed controller will be mounted outdoors in all kinds of weather conditions, exposed to heavy humidity or come into direct contact with water and other liquids, it must be in a water-resistant enclosure. KB Electronics is experienced with providing speed controllers for applications in all kinds of environmental conditions, with enclosures rated IP20, NEMA 1/IP50 and NEMA 4X/IP65.

Having the right accessories means that you can make the most of your speed controller and further customize it for your specific requirements. With a range of optional extras, including signal isolators, line filters, multi-speed boards, memory modules, switch kits and more, a comprehensive supplier like KB Electronics can provide you with all the parts you need to fine-tune every part of your application.

Choosing the right speed controller for your electric motor involves making a thorough analysis of the motor type, operational requirements, power supply, control system infrastructure and operating environment, and choosing a solution that is perfectly customized to your needs. KB Electronics offers a comprehensive, affordable and highly flexible range of modern, high-performance AC and DC speed controllers for applications ranging from domestic appliances to large industrial projects, along with all the tools and accessories you need to rapidly install, integrate, optimize and troubleshoot your operation.

This article was submitted by eMotors, an online source for electric motors, gear reducers and controls in Canada. eMotors Direct carries a full line up of electronic soft starters in 30 warehouses across Canada, including such popular brands as ABB, WEG and Motortronics.