AC motors can be operated directly from AC supply voltage, but this is only suitable if the motor is required to run at constant speed. If the speed or load requirements of the motor change, an AC drive — also referred to as a variable frequency drive (VFD) — can vary the voltage and frequency […]
FAQs + basics
FAQ: Is a PLC fast enough to meet my application’s requirements?
Knowing if your PLC is fast enough and can handle your application is really a two-part process. That is, it can be looked at from two different but intertwined perspectives; one is from the PLC perspective and the other is from the application level. The most important factors are knowing the specifics of the application […]
FAQ: What is stepper drive idle-current reduction and why does it help?
When stepper motors operate, they operate by drawing current continuously. This method of operation ensures more accurate positioning and more consistent torque. However, this also means an increase of energy they use and the amount of heat they produce. This holds true even when the stepper motor is idling. Idling is not a very efficient […]
FAQ: How do drives for switched-reluctance motors work?
Switched-reluctance motors are stepmotors that accept power to their stators (instead of their rotors) to use output mechanical force through the use of reluctance. This is magnetomotive force to magnetic flux. Switched-reluctance motors use drives that differ from those that pair with other stepper motors. That’s because switched-reluctance motors have nonlinear magnetic behavior … but output high […]
FAQ: What is dynamic braking and when is it used?
When a motor is in an overhauling condition—that is, the load is moving faster than the designated motor speed—the motor acts as a generator and produces electrical energy from mechanical energy. This electrical energy, however, needs somewhere to go, and the most common way of dealing with its release is through dynamic braking. How dynamic […]
FAQ: What are regenerative drives and where are they used?
The main purpose of a motor is to convert electrical energy into mechanical energy. But when the motor’s synchronous speed is less than the rotor speed, the motor acts like a generator and converts mechanical energy into electrical energy. This energy is typically fed back into capacitors in the DC bus, but the bus can […]
FAQ: What are some PLC I/O, visual display, and networking options?
A PLC can be a highly customizable controller, depending on application needs. And with advances in technology, the options designers have continue to expand. Specifically, we focus here on three types of options; I/O (input/output), visual displays, and networking. I/O I/O options can be classified in several ways, including some basic groupings such as analog […]
FAQ: When are closed-loop and open-loop vector control useful?
AC drives have historically been controlled by a scalar method known as volts per hertz (V/Hz), in which the drive maintains a constant voltage-to-frequency ratio in order to maintain stable torque production. However, the V/Hz control scheme doesn’t allow tight speed regulation and is limited in its ability to produce torque at low speeds. Vector […]
FAQ: What is V/Hz control mode for AC drives?
AC motors are commonly paired with variable frequency drives (VFDs), which control motor speed by regulating the frequency of the supplied voltage. Depending on the application and level of speed regulation required, VFDs can be controlled by either scalar or vector methods. The most common type of VFD control is a scalar method referred to as volts […]
Motion controllers help planes take precision aerial photos of disasters
Quick response to catastrophes such as floods and fires is critical, but disaster sites are often inaccessible and unsafe for inspectors and adjusters who come after first responders. Now Pictometry, an EagleView company, collects and supplies ultra-clear aerial photography to let insurance carriers, restoration companies, utilities, and contractors identify safe-access points, areas of total loss, […]