The term HVAC is an acronym that stands for Heating, Ventilation, and Air Conditioning; it broadly describes systems that provide heating and cooling to commercial and residential buildings for environmental comfort. A typical HVAC system includes Heating equipment, Ventilation equipment, and Air-Conditioning or Cooling equipment; the functions of these three elements are interrelated, particularly when providing thermal comfort and acceptable indoor air quality. For example, the Heating element, which may be a boiler or furnace, includes a piping system for the heat-carrying fluid or ductwork in case of a forced air system. The Ventilation element (either natural or forced) uses fresh outdoor air to provide high-quality indoor air through a process called ventilation–a process of exchanging or replacing air within a designated space. This process also involves the removal of dust and smoke particles, moisture, airborne bacteria, heat, odors, carbon dioxide, and other unwanted gases...
A typical Metal Oxide Varistor (MOV) is generally made of a combination of Zinc Oxide and other types of metal oxides such as Cobalt, Bismuth, and Manganese oxides. The metal oxide substance is arranged between two metal electrodes or plates with no polarity (no positive or negative sides) to interact with each other; so, the two leads of the MOV can be connected in any direction since they conduct electric current in both directions. The Zinc Oxide arrangement gives the MOV similar Volt-Ampere characteristics (V-I characteristics) as a Zener diode. Such that when a moderate or small voltage is supplied across the MOV’s electrodes, only a small amount of current will flow through due to the high resistance of the MOV. If a large voltage is applied across the MOV, its resistance value will decrease significantly and a large amount of current will flow through it. If the flowing current rises to a particular point, known as the breaker point (break over voltage), the zinc oxide...
The PowerFlex Human Interface Modules (HIMs) are used for configuring and monitoring of PowerFlex AC drives and their attached peripherals. These HIMs are available with most PowerFlex drives and come with a high-definition LCD. They support several languages and give practical explanations of parameters and events, so you don’t have to look through a handbook for specifics. This article discusses HIM’s features, types, components, and compatibility with AC drives. This information will help you to choose a suitable HIM for your application. HIMs are categorized into following categories. Allen Bradley 20-HIM-A3 Basic PowerFlex 7-Class HIMs: 20-HIM-A3 and 20-HIM-A5 are basic PowerFlex 7-class HIMs. 20-HIM-A3 is an LCD operator interface that is compatible with PowerFlex 70, 700, 700H, 700S, and 700L AC drives. This basic HIM features a liquid crystal display along with a full numeric keypad as an operator interface. You can either use this HIM as a hand-held device or mount it...
The term HIM stands for Human Interface Module. It’s basically a user interface that enables human operators to engage and interact with a drive, machine, or a system. HIMs are commonly used in the industrial context, and you’ll often come across them in industrial environments alongside AC drives or Variable Frequency Drives (VFDs). They allow factory operators to start and stop process cycles, adjust operating set points, and perform other necessary functions required to control and interact with industrial drives. HIMs are also software-based, so they replace physical and hard-wired controls with software control parameters, allowing easier adjustment of drive operating parameters. Thus, with a HIM you can upload individual sets of parameters for your host drive and any other peripherals connected into the HIM. Other functions include: Accepting input data obtained from human operators Processing the input data Data logging Real-time information display of the operating conditions...
Drive or Electric Drive is an electromechanical system that necessarily uses an electric motor or a prime mover. In this system, the motion of the electric motor is controlled to make it applicable and useful for some applications in the realm of industry, automotive, domestic use, hospitals, etc. In an electric drive system, energy conversion is controlled. Motor, control systems and power converter (power electronics) are major components of electric drive. The selection or construction of various drive components varies depending upon the application and environment where the system is to be used. DC bus is part of the power electronics part of the drive. Its stability and voltage control are crucial to gaining good results for the drive system. The Drive system is a complex electrical system. As mentioned earlier, the following are its major components Electric Motor Controller Power Converter or Power Electronics Section These three components are complex systems in themselves...
Drives that control motor speed such as Variable Frequency Drives (VFDs), AC Drives, and Variable Speed Drives (VSDs) include a rectifier unit, in which the AC voltage is supplied to the drive is converted into DC voltage. In most of these motor drives, this rectifier unit makes use of standard P-N junction diodes (two-layer diodes) to build different types of rectifier circuits like half-wave, bridge, and full-wave rectifiers. However, if high voltage is applied to any of these two-layer diode rectifiers, its diodes are likely to get damaged. For this reason, motor drives using rectifier units made of P-N junction diodes cannot operate reliably at high supply voltages. To overcome this limitation, a special type of rectifier that could withstand high voltages was developed. This rectifier is the Silicon Controlled Rectifier (SCR). SCRs are often used in applications where a large amount of power needs to be switched, though it’s necessary to keep their control voltage and current low...
In industrial automation, the term “drive” is often associated with motor drives, which are types of motor controllers described using various terms such as Variable Speed Drives (VSDs), Adjustable Speed Drives (ASDs), Inverter Drives, Adjustable Frequency Drives (AFD), Variable Frequency Drives (VFDs), AC Drives, Variable-Voltage Drives, …etc. However, even though these terms are used interchangeably, they have different meanings depending on the technique used to control the motor speed and the drive’s application. For example, a Variable Speed Drive is a more generic term that applies to electronic or mechanical devices which control either motor speed or the speed of motor-driven equipment like compressors, fans, pumps, etc. Whereas, a VFD is a device that uses power electronics to vary the frequency of the input voltage to a motor, thereby controlling the motor speed. On the other hand, an Adjustable Speed Drive is also a more generic term that applies to both electrical and...
Allen Bradley MPL Servo Motors A servo motor is a linear or rotary actuator that allows for precise control of linear or angular position, acceleration, and velocity. A typical servo motor system consists of a suitable electric motor coupled to a sensor for position feedback. The motors’ control circuit, which includes the position sensor, provides feedback on the real-time position of the motor shaft. With this feedback, the servo motor can rotate with great precision. But for a servo motor system to be complete, it also requires a servo drive that uses the position feedback sensor to precisely turn the servo motor at some specific angles or distances. Simply put, a servo motor is just a simple electric motor that runs through a servo mechanism. Servo motors are broadly categorized as AC-powered or DC-powered. But there are many other classifications depending on the operating characteristics and gear arrangement of the servo motor in question. The different types of gear...
A Variable Frequency Drive (VFD), also known as a Variable-Speed Drive (VSD), Adjustable-Frequency Drive (AFD), Frequency Converter (FC), Adjustable Speed Drive (ASD), Microdrive, AC drive, or an Inverter driver, is an electronic controller used to regulate the rotational speed of induction or synchronous electric motors. The VFD controls motor speed by varying the frequency of the supply voltage being used to power that motor. To practically execute this, a typical VFD system consists of four main components; namely, the Rectifier Circuit unit, DC Bus and Filter unit, Inverter Circuit unit, and the control unit. These four units function together to adjust the AC frequency of the voltage supplied to a connected motor, thereby controlling the motor’s RPM (motor speed in revolutions per minute). First, the VFD takes in fixed frequency AC voltage into the rectifier section, which consists of diodes (4 or 6) or thyristors that convert the input AC voltage into unfiltered DC voltage. This...
Programmable Logic Controllers are ruggedized computers, specially designed and built to operate reliably under harsh industrial environments. A typical PLC system consists of a processor (CPU), programmable memory, power supply, a user-defined program, I/O modules with associated circuitry, and so on. The programmable memory stores a series of instructions that enable the PLC to perform various control functions like arithmetic computation, relay logic, timing, counting, and sequencing. Essentially, these control functions are used to monitor and control either individual machines or complex electro-mechanical processes through the PLC inputs and outputs. As the PLC processor reads the inputs, the PLC processes them through the stored user-defined program and generates outputs that are sent out as control commands to field output devices. The I/O modules in the PLC system provide digital or analog electronic connections to field input and output devices. In this modern era, PLCs are...
VersaView and PanelView are Allen-Bradley operator interfaces from Rockwell Automation, with similar functionalities as Human-Machine Interfaces (HMIs). These graphic operator terminals combine HMI software and hardware to allow users to interact with a controller and the system being controlled. An HMI terminal can vary from a physical control panel with indicator lights and keypad buttons to an industrial PC (IPC) with color graphic displays and which runs a dedicated software. The Allen-Bradley PanelView and VersaView are both popular operator terminals in a variety of industrial control applications requiring the display of information graphically, real-time monitoring, and control of various industrial processes. They enable operators to understand the status of a controller fast enough, so as to make informed control decisions regarding the machine or process being controlled. Allen-Bradley PanelView Terminal Allen-Bradley PanelView terminals provide rugged, graphical interface...
In general, the concept of Sourcing and Sinking details a current flow relation between input and output devices of a control system and their power supply. This concept is based on the basic electrical theory, which states that; to complete an electrical circuit, the conventional current should flow from the DC+ terminal through a load to the DC- terminal. In that regard, the two terminologies (Sinking and Sourcing) apply only to DC input and DC output circuits. And not to AC circuits because of the reference to positive (+) and negative (-) polarities. In PLC systems, the Sinking and Sourcing concept may be confusing to most people but it’s fairly a simple one. As Sink and Source logic circuits are mainly associated with digital PLC Input and Output (I/O) signals. A logic circuit is basically an electrical I/O circuit in which its output is a function of the input. Such circuits are defined by the type of components used and the direction of current flow. A simple logic circuit can...
VFDs or Variable Frequency Drives are controller systems including motors that give varying output speed as per input command. The capacitor forms DC links the whole VFD system. The voltage across this DC link is an important parameter to be controlled. This voltage is input to the inverter and thus acts as a reference voltage in the system. Variations in DC link voltage or voltage across the capacitor impacts the speed and performance of motor greatly. The selection of capacitor is equally important as its size will define the ripple factor, noise, and smoothness in the running of the motor. While it is important to know the significance and working of capacitors in a drive system, let’s understand the basics of the drive system, associated terminologies, and common topologies. To understand the purpose of capacitors in VFDs, one should have an idea of the purpose of VFDs and their basic work topology. Variable Frequency Drives are electromechanical systems in which the speed and...
The term VFD stands for Variable Frequency Drive. It is a type of motor controller which drives an electric motor by varying the frequency and voltage supplied to that motor. Variable Frequency Drives (VFDs) are also known as AC Drives, Inverters, Variable/Adjustable Speed Drives, Inverters, Variable-Voltage Drives, Microdrives, Frequency Converters, or Variable Frequency Inverters (VFIs). Frequency, given in Hertz (Hz), is directly related to motor speed in revolutions per minute (RPM). Thus, by adjusting the input frequency the motor speed can be varied accordingly. For example, the higher the supply frequency, the more RPMs the motor will exhibit. VFDs are best suited for applications in which an electric motor is not required to run at full speed, as they can ramp down the supply voltage and frequency to meet the requirements of the motor’s load. In case there is a change in the application’s motor speed requirements, the VFD can be set to ramp up or turn down the motor speed as...
An MP-Series Low-Inertia Servo Motor (Cat. No. MPL-B320P-MJ22AA) MPL servo motors are a family of MP-Series™ low-inertia rotary servo motors, from Rockwell Automation under Allen-Bradley Bulletin MPL. They are compact and highly dynamic brushless servo motors consisting of premium permanent magnets. They feature multi-turn or single-turn high resolution encoders, and they are available with 24 Volts DC brakes. The MPL units use innovative design characteristics and advanced winding technology to reduce motor size while delivering considerably higher torque. They thus leverage their high torque-to-size ratio to provide high-performance motion systems, which require servo motors with quicker acceleration and excellent torque performance. The MP-Series™ low-inertia servo motors are typically used with PowerFlex drives and Kinetix drives from Allen-Bradley. The Allen-Bradley® MPL servo motors feature two input voltage classes: 400V-class and 200V-class. They are available in nine (9)...