frequency converter
frequency converter
(OP)
why is it that the frequency converter input voltage is not the same for the output voltage and the reading is more higher than the input
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RE: frequency converter
RE: frequency converter
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RE: frequency converter
RE: frequency converter
For example, with the exception of VFD's with voltage doubler front ends, the effective PWM equivalent voltage that is sent to the motor (output of drive) cannot be higher than the input RMS voltage.
That is because the output equivalent voltage is limited by the DC bus voltage which, in turn, is limited by the peak value of the incoming AC voltage. So, for example, if you put 460VAC into a VFD, the maximum output to the motor will not exceed 460V. If, on the other hand, you supply a drive with 502VAC, you can send up to 502V to the motor.
RE: frequency converter
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If we learn from our mistakes I'm getting a great education!
RE: frequency converter
Putting a step-up transformer before the rectifier wasn't considered too difficult a challenge :)
RE: frequency converter
And, yes, it seems we are assuming the inverter is an electronics-based probably PWM design. Certainly, a mechanical frequency converter has no voltage limitations either up or down.
RE: frequency converter
RE: frequency converter
If you supply more details about exactly what you are working on or planning to work on, maybe we can be more specific as to how it is going to work in your situation.
If this is a general question on how inverter drives function, please indicate that as well, but this is not a Learning Center for the curios amateur, the primary function of this forum is to assist working engineers with getting over specific problems. If you are completely unaware of the functioning of an inverter drive, I suggest a thorough search of learning resources in whatever your native language is as a place to start, then if you are working on something and get stumped, come back and ask for help.
"If I had eight hours to chop down a tree, I'd spend six sharpening my axe." -- Abraham Lincoln
For the best use of Eng-Tips, please click here -> FAQ731-376: Eng-Tips.com Forum Policies
RE: frequency converter
RE: frequency converter
The actual motor voltage is composed of pulses with varying width that are 'cut' out of this DC voltage by the IGBTs in the drive. If you filter high frequency components away from this pulse train (Pulse Width Modulated, hence PWM), you will get the voltage representing the motor voltage, which is somewhere between zero and mains voltage, depending on speed an control mode. In scalar control, the voltage is roughly proportional to motor frequency and in vector control mode, it is usually lower than expected because vector control usually optimizes mis fully loaded.
If you measure motor voltage without any filter, you will see the sum of fundamental an all switching components and that usually means that you see a lot more voltage than mains voltage.
That does not mean that the inverter outputs more than mains voltage - only that you are using the wrong measurement method and also not interpreting the result correctly.
You are starting a long and fascinating journey. Be prepared to meet many more things that you don't understand at first. You will understand as you proceed.
Gunnar Englund
www.gke.org
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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
RE: frequency converter
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"If I had eight hours to chop down a tree, I'd spend six sharpening my axe." -- Abraham Lincoln
For the best use of Eng-Tips, please click here -> FAQ731-376: Eng-Tips.com Forum Policies
RE: frequency converter
RE: frequency converter
RE: frequency converter
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If we learn from our mistakes I'm getting a great education!
RE: frequency converter
When you have digested the Control Technique's handbook, I recommend Werner Leonhard's 'Control of electrical drives' from Springer. It is little more demanding, but does explain things that Control Techniques doesn't go deeply into.
Gunnar Englund
www.gke.org
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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...