Blog of motion control, electrical machinery, automation, process control, motor control, green energy...

Estimating Fan Energy Cost Example


Pumps and fan systems account for almost 40% of all motor applications in industry. The input power of a fan is proportional to cube of the flow. For instance For example, if 100% flow requires full power, 75% flow theoretically requires (0.75)3 = 42% of full power. Although this is the theoretical saving under zero static head conditions, even in practical applications, a substantial energy saving can be achieved. Most energy savings from the application of VSD's are available in the use of centrifugal fans or pumps. When estimating the saving from such applications, it is useful to use the Fan Laws, which relate air (fluid) flow, input power and motor speed.
...

The quad timer is an extremely flexible module, providing all required services relating to time events. The application uses four channels of the quad timer for:

-- One channel for PWM-to-ADC synchronization

...

The slow control loop executes speed and field-weakening controllers and lower priority control tasks. The PI speed controller output sets a reference for the torque producing quadrature axis component of the stator current (isq). The reference for flux producing direct axis component of the stator current (isd) is set by the Field-Weakening controller. The Adaptive Circuit performs correction on the rotor time constant to minimize the error of the rotor flux position estimation.
...

To be able to decompose currents into torque and flux producing components (isd,isq), we need to know the position of the motor magnetizing flux. This requires accurate velocity information sensed by a speed or position sensor attached to the rotor. Incremental encoders or resolvers are naturally used as position transducers for vector control drives. In cost sensitive applications like washing machines, tachogenerators are widely used. In some applications the use of speed/position sensors is not desirable either. Then, the aim is not to measure the speed/position directly, but to employ some indirect techniques to estimate the rotor position instead. Algorithms which do not employ speed sensors are called "sensorless control".
...

The control algorithms can be sorted into two general groups. The first group is referred to scalar control. The constant Volt per Hertz control is a very popular technique representing scalar control.

The other group is called vector or field oriented control (FOC). The vector oriented techniques bring overall improvements in drive performance over scalar control. Advantages of FOC: higher efficiency, full torque control, decoupled control of flux and torque, improved dynamics, etc.

The basic idea of the vector control or field oriented control (FOC) algorithm is to decompose a stator current into flux and torque producing components. Both components can be controlled separately after decomposition. The structure of the motor controller is then as simple as that for a separately excited DC motor.

 
Figure 2.  Vector Control Transformations

Figure 2 shows the basic structure of the vector control algorithm for the AC induction motor. To perform vector control, it is necessary to follow these steps:

-- Measure the motor quantities (phase voltages and currents)

-----------------------------------------------------------

Powtran Technology Co.,Ltd. (Shenzhen POWTRAN Technology Co., Ltd., DaLian POWTRAN Technology Co., Ltd.)

The AC Induction Motor (ACIM) is a rotating electric machine designed to operate from a 3-phase source of alternating voltage. Slots in the inner periphery of the stator accommodate 3-phase winding a,b,c. The turns in each winding are distributed so that a current in a stator winding produces an approximately sinusoidally-distributed flux density around the periphery of the air gap. When three currents that are sinusoidally varying in time, but displaced in phase by 120° from each other, flow through the three symmetrically-placed windings, a radially-directed air gap flux density is produced that is also sinusoidally distributed around the gap and rotates at an angular velocity equal to the angular frequency of the stator currents.

The most common type of induction motor has a squirrel cage rotor in which aluminum conductors or bars are cast into slots in the outer periphery of the rotor. These conductors or bars are shorted together at both ends of the rotor by cast aluminum end rings, which also can be shaped to act as fans

a pdf document about VFDs

An ac variable speed drive system controls the speed of an ac motor by controlling the frequency of the power supplied to the motor.

Variable frequency drive (VFD) is an excellent choice for adjustable-speed drive users. VFD allows an operator to fine-tune processes and at the same time, reduces the costs for energy and equipment maintenance.

                   How's the market of frequency converter in 2009

Variable frequency inverters are used for electronic speed control of AC induction motors. We all know that the needs of the market are wide and varied. And I have expericed that wide market. And before the financial crisis, the market report from all kinds of research institutes says the market is huge and will experience a high speed growth.

...

Welcome to leave your comments on my posts on this blog

Hi, I am Sarah, an ordinary engineers of vfd. I will post some articles about vfd, frequency converter on this blog. I hope to share my experience with you about this item. I will leave my message about this ac drive here. And I really expect you can leave your comments on my posts. Hope we can communicate with each other about this industrial equipment.

...

Blog is launched

After several months, we launch the blog of engineers and users in the field of ac drive, frequency converter. We hope this blog will be a good community in the field of frequency inverter and vfd for users and engineers. And we also hope this blog will be a blog that all of you can share your ideas and experience of ac drive. We can talk everything about variable frequency drive here.