Instrumentation Engineers

The modern process control demands more versatility in the equipment operation. Sometimes the process will demand more draft from a fan, or reduce a belt speed, others increase the feed from a rotary valve. These are some examples of the use of the Variable Frequency Drives in the industry.

VFD is the acronym for Variable Frequency Drive and there are multiple applications for a VFD in the industry. Their use has been increasingly spreading in different areas as the technology and price make them more accessible for the general costumers.

How a VFD actually works? It controls the speed of the motor by modifying the base line frequency.

The motor speed is determined by the equation:

Ns = 120 (f/p)

Where Ns is the synchronous speed, f is the line frequency (60Hz America, 50 Hz Europe) and p is the number of pole pairs that the motor has.

Without a VFD the standard (60 Hz) motor speeds for two poles is 3,600 RPMs, four poles 1,800RPMs, six poles 1,200 RPMs, etc. So, how can we modify the speed of the motor? What the VFD does is to decrease or increase the line frequency. For example, to get a 50% of the speed of a motor, the equivalent frequency is 30 Hz.

A VFD has four major components: Rectifier, DC-Link, Inverter, and Controller. The incoming power lines go to a Rectifier that converts the sinusoidal voltage into a Steady DC output with the use of diodes. The DC-Link tries to keep a steady and free of spikes voltage with capacitors and inductors. The inverter takes the voltage from the DC-Link and converts it to a sinusoidal wave again but not necessarily back to 60 Hz using IGBTs. The Controller monitors and direct every single step of this process and interacts with the control interfaces (communications, HMI, etc.).

Maybe all this seems a little bit confusing, let’s get back to the real world. Have you ever seen a Car Inverter? They feed by a cigarette lighter plug and it converts the DC Voltage from the car to 120 VAC. In a Car Inverter, you can plug any kind of low power electric component (i.e. laptop) as in a regular plug. The difference with a VFD is that they have a previous rectifier step and they can control the output frequency.

We talked previously about diodes, capacitors, inductors and IGBTs, all of them are electronic components and some are semiconductors. One of the biggest reasons the VFDs are getting popular is because of the increase of the reliability and the price drop of power electronic components.

What a VFD can actually do? It can control the start acceleration; run a motor from a different range of speeds and slow down when the process pushes the motor to accelerate.

All the power that the motor is going to demand will pass through the power electronic elements of the VFD. If the load has peaks, then the VFD will need to be rated to a higher load. This is necessary because the internal elements have current and power limits. The life of the power electronics elements is reduced if they are demanded to their maximum capacity causing the VFDs to go bad.

Understanding how a VFD operates is the first step to find applications where they can be useful. A VFD is a tool that can help to make processes more efficient as they become more versatile and accessible to the general industry.

https://www.youtube.com/watch?v=Y8m6kgaES2U

Shut off valve problem due to forced spring Shut off valve problem due to forced spring

PROFINET VS PROFIBUS

Some flow transmitters called Multi variable that's why they measures dp , p and temperature then through an internal equation calculates the flow rate taken in consideration the or***ce data such as bore size , coefficient factor and so on.
So, easily can get 4-20 mA corresponding to the flow rate.
In the picture the method of calibration of FT device using hand pump applying manually the requested pressure through a measurement device to verify their readings.

Ex. Fully compensated transmitter Rosemount MV3051

How Ultrasonic Flowmeters Work

Ultrasonic flowmeters use sound waves to determine the velocity of a fluid flowing in a pipe. At no flow conditions, the frequencies of an ultrasonic wave transmitted into a pipe and its reflections from the fluid are the same. Under flowing conditions, the frequency of the reflected wave is different due to the Doppler effect. When the fluid moves faster, the frequency shift increases linearly. The transmitter processes signals from the transmitted wave and its reflections to determine the flow rate.

Transit time ultrasonic flowmeters send and receive ultrasonic waves between transducers in both the upstream and downstream directions in the pipe. At no flow conditions, it takes the same time to travel upstream and downstream between the transducers. Under flowing conditions, the upstream wave will travel slower and take more time than the (faster) downstream wave. When the fluid moves faster, the difference between the upstream and downstream times increases. The transmitter processes upstream and downstream times to determine the flow rate. They represent about 12% of all flowmeters sold.

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Reversing an actuator from fail close to fail open.

https://youtu.be/xJEQkKDv8NU

Converting Rack and Pinion Actuators to Reverse Acting Instructional video: converting rack and pinion actuators, 2R 300 SR fail counterclockwise, to reverse acting by A-T Controls.

https://youtu.be/MjfBXeoPKsU

Control Valve Actuators Control valve actuators control fluid in a pipe by varying the or***ce size through which the fluid flows. Control valves contain two major components; the v...

Overloading Electronics!

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Switch gear board.

Multi-drop network