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The good of PLC is it work in a hazard environment and robust. We have Omron CQM1 for DI water plant, after a big flooding in Thailand ( stay under water for more than 2 months) after we clean dry and bake ( remove every single board into basket) and re-assembly it back and upload a backup ladder program, it work wonderfully.
Clean the variable frequency drive heatsink and check or replace the fans. I like new fans every five years. I also double check the drives installation. This is a good opportunity to make corrections to the install like conduits or cable routing. Check the connections but don't give the terminals a crank. They should be re-tightened after a couple of weeks after the commissioning. After that giving them a crank every preventive maintenance is asking for a broken terminal. At our facility we have drive that have run for 20 years with preventive maintenance performed every six months.
Over-sizing the machine as an alternative. It did not work in my motors as the design had brazed rotors. Rotor losses will increase due to over-sizing and heat accumulated faster than the reduction in the starting time. This is bad during commissioning when frequent successive starts are taken. The heat generated in the rotor is normally the limiting factor. Variable speed drive is a good solution, but not economical in many cases.
What about the frequency of the small amount of the power which back to the network its depend on the speed of the rotor and number of poles f=60/N.P? In another word assume I have AC generator give AC power source what is the voltage and frequency of this power? How to calculate it?
Dithering the switching frequency of a SMPS (SSFD) introduces sideband energy that by the conservation of energy must result in a reduction in harmonic-peaks. There are two important characteristics of a frequency-modulated waveform bandwidth rule.
In a loop circuit in which the only component is a simple resistor, that resistor is the only thing in the loop that actually "resists" current flow. Apply a DC voltage to a loop without that resistance and current quickly rises...not to theoretical infinity...but until the wire melts or breaks..because the wire (not a perfect conductor) is a resistor itself.
In the days before networked motors, all inputs were accounted for in the Input list and all outputs were accounted for in the Output list. The IO count was then evaluated to help determine the complexity of a system. IO counts directly impacted many various costs in the project such as cost of hardware, cost of wiring, and the cost of installation. The complexity of the system was used to estimate how much engineering time would be required for the project.
Here I have very basic questions which I couldn't get when I searched in internet or in books. I am very new to my profession not aware of these things which I often face in my work. Please spend some time for answering my questions or showing me a way by referring some good material or books.
Variable speed drives have come a long way in the past 20 years, from being a dumb component to intelligent process controller. Following are the main points to consider:
Even with a constant speed you will have to start and stop the motor. If you just have an IGBT power block producing a fixed frequency you will have to deal with the high inrush current, 3-5 times FLA. The are several companies that make chassis or open style VFDs that can be around 30% less than the standard IP20 versions with all the fancy stuff.
How to measure or diagnose common mode voltage of three phase PWM variable speed drive? And how to solve EMI from motor Driver?
For your first question: Could you let me know your definition of variable speed drive "common mode"? Is this the voltage between one phase IGBT leg and the neutral point of stator "Y" connected machine?
A motor manufacturer assigns a RATING to the motor, which is put on the motor rating plate.( OR IN THE CATALOG)
As the rating plate mentions RATED output and RATED speed, RATED torque is derived from these.
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service VSD blog: A deep observation of automation control industry, especially in AC motor variable speed drive for industrial motor controls.

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