Overload ratings for AC drives typically specify the overload percentage and duration. The
duration may be specified as a duty cycle, such as 1 minute out of every five minutes.
Enclosure Ratings
Enclosure ratings identify an enclosure's ability to resist external environmental influences.
In North America, ratings found in the following publications are most commonly used.
National Electrical Manufacturers Association (NEMA Standard 250)
Underwriters Laboratories, Inc. (UL50 and UL 508)
Canadian Standards Association (CSA Standard C22.2 No. 94)
The rating numbers described in these publications are used to identify the degree of protection provided by each enclosure type number. UL and CSA require enclosure testing, but NEMA does not. The accompanying chart shows a summary of the degree of protection provided by selected enclosure types.
Enclosure ingress protection (IP) rating numbers are also provided by the International Electro technical Commission (IEC publication 60529). These rating numbers are commonly used in Europe and other parts of the world. Each rating number has two digits. The first digit is the degree of protection against access to hazardous parts and the degree of protection from foreign objects. The second digit is the degree of protection from water.
Point your mouse on the red rectangle to see a summary of these IP rating numbers.
Introduction To Programming Parameters
Most AC drives can have their settings customized to optimize the drive for the specific application. These settings are typically referred to as parameters. All AC drive manufacturers have slightly different terms for their specific parameters, but the types of functions performed are similar.
The accompanying graphic shows Siemens Advanced Operator Panel (AOP30). The AOP30
and a program called Starter are tools to help support the user during: parameterization, commissioning, diagnosis, and service of Siemens SINAMICS and MICROMASTER 4 drives.
Depending on the drive, other operator panels are also available.
The AOP30 communicates with the drive via a serial interface. LEDs on the operator panel indicate the status of the drive. The panel includes a 26-key touch-sensitive keypad and 240 x 64 pixel back-lit display.
Starters:
Starter is used with Siemens SINAMICS and MICROMASTER 4 AC drives for commissioning, optimization, and diagnostics.Starter can be used by itself or as part of the Siemens Totally Integrated Automation engineering tool, Drive ES. In addition, Starter can be integrated in another Siemens program called SIMOTION Scout that is used for motion control applications.Initial drive commissioning is done through wizards which allow the user to get the drive up and running with only a few parameter settings.Self-optimization functions, such as self-tuning, simplify the effort of optimizing the drive. Depending upon the drive, a built-in trace function can provide additional support during commissioning, optimization, and troubleshooting.
Parameters And Function Block:
Parameters are used to provide instructions to a drive. For a Siemens drive, each parameter is designated by a lower case r or p and an assigned number. For most Siemens drives, there are three types of parameters: display parameters, adjustable parameters, and BICO parameters.Display parameters, sometimes called visualization parameters, are used to display internal quantities. Display parameters are read-only and cannot be changed by the operator.
output to the motor. A function block consists of several parameters grouped together to perform a specific task. The response of a function block is determined by adjustable parameters, sometimes called function parameters. Adjustable parameters have an associated variable that can be set within a designated range.
Acceleration/deceleration times are examples of variable parameters. Other examples of variable parameters are proportional gain and integral time. These parameters determine the response of a PI-controller. Each parameter has a name, identifying number, value range, and a factory setting.
BICO is a term used to describe a method of connecting function blocks. BICO is a contraction of two terms, binector and connector. With BICO parameters, you can determine the source of the input signal to a function block. This allows the user to soft-wire function blocks to meet application requirements.
Indexing And Data Sheet:
In many applications, it is desirable to configure the drive for variations in operation. For example, there may be a situation in an application where it is desirable to have different acceleration times. This can be done using indexed parameters.Indexed parameters can have multiple values stored with them. Each value stored is part of a data set. For example, parameter p1120, acceleration time, is an indexed parameter that can have four different acceleration times stored. For example, p1120 could have the
PI Controller:
PI (proportional-integral) controllers are commonly used function blocks. A PI controller provides a response to an error signal that is the sum of two values, one is
proportional to the error signal and the other is representative of the amount of error over
time. Combining these two responses in one function block improves the dynamic response of the system. In the accompanying example, the difference between the desired speed and the actual speed is the input to the PI controller. When the difference is zero, no change in speed is required.
One factor that could cause a speed error is a change in load. For example, a sudden increase in load causes a motor to slow down and a sudden decrease in load causes a motor to speed up. A speed error also occurs whenever the desired speed is changed. Until the motor reaches the new desired speed, there will be a deviation.
The PI controller's job is to make speed corrections quickly and with a minimal amount of overshoot and oscillation. Proportional gain and integral time are used to tune the PI controller's performance. The end result should be a fast response time with about a 43%
initial overshoot. The motor should then settle in to the new desired speed.
Free Function Block And Bico Parameters:
Most Siemens drives offer an extensive library of freely configurable function blocks including logic blocks, arithmetic function blocks, and control-loop blocks. These free function blocks are interconnected using BICO parameters. BICO parameters are also used to assign a digital input or output to a free block. This allows the user to soft-wire function blocks to meet specific application requirements. Free function blocks and BICO parameters provide most Siemens drives with the ability to perform basic PLC functions within the drive, reducing the need for additional hardware and software.
Drive Control Chart:
For even greater functionality Drive Control Charts (DCC) can be enabled (license required). Drive control charts provide a high degree of flexibility and can be easily implemented using pre-configured blocks for logic, arithmetic, and control functions. This also allows customized macros to be created for commonly used functionality. In addition to PLC functionality, drive control charts incorporate freely configurable, modular drive-related functions including open-loop and closed loop control from a simple control unit up to an axial centre winder. Drive control charts also facilitate graphic configuring and online diagnostics.Key Customer Benefits: Increased capability for innovation
Improved plant and system productivity
Reduced engineering cost
Higher return on investment
The term constant torque implies that the torque required to keep the load running is the same throughout the speed range; however, this is not exactly correct. In this context, constant torque actually refers to the motor's ability to maintain constant flux. The actual torque produced does vary with the load and peak torques in excess of the rated continuous torque can occur at any speed.
One example of a constant torque load is a conveyor. Conveyors are found in all sorts of applications and environments and vary widely in terms of their capabilities.
Conveyors
Many conveyors are made up of belts which support the load; drums or pulleys, which support the belts and maintain tension; and idlers, which support the belts and loads. Keep in mind that many conveyors have multiple sections and some sections may need to run at different speeds than others. For these applications, multiple AC drive-motor combinations are used with the drives networked for coordination.
Constant Horsepower Application
Constant horsepower applications require a constant force as the radius changes. One example is a winder application. For such an application, the radius increases as material is added to a roll. Similarly, in an unwinding application, the radius decreases as material is removed. In either case, the tension on the material must be controlled. Another constant horsepower application is a lathe spindle. The rotating motion of the work piece being machined on a lathe is controlled by a spindle drive. The spindle drive must maintain a constant surface speed as material is removed from the work piece. This requires the motor speed to increase as the radius of the work piece is reduced. In addition, as the radius of the work piece decreases, because torque is the product of the force applied times the radius, the torque required by the load also decreases. As a result of this inverse relationship between the load torque required and the motor speed, the motor can be operated above