VFD?s & Building Wire

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weressl said:
As I pointed out before ASD is the officially adopted acronym by IEEE.
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...as a generic term for speed control devices / systems. It still does not delineate the specific method even if used in context. In other words, if the context of a discussion is AC motors and you use the term ASD, that still doesn't preclude a Varidrive (mechanical V pulley system) or Eddy Current drive / clutch.
 
Jraef said:
...as a generic term for speed control devices / systems. It still does not delineate the specific method even if used in context. In other words, if the context of a discussion is AC motors and you use the term ASD, that still doesn't preclude a Varidrive (mechanical V pulley system) or Eddy Current drive / clutch.
Click to expand...

You may want to take it up then with IEEE.

PC used to mean Programmable Controller, until it was hijacked by the computer hacks and forced the IEEE to revise the acronym to PLC.

PFC is both Private, First Class and Power Factor Correction.

...and so on and so forth.:smile:
 
weressl said:
You may want to take it up then with IEEE.

PC used to mean Programmable Controller, until it was hijacked by the computer hacks and forced the IEEE to revise the acronym to PLC.

PFC is both Private, First Class and Power Factor Correction.

...and so on and so forth.:smile:
Click to expand...

No one is questioning what the acronym 'ASD' stands for, just what the exact definition of 'Adjustable Speed Drive' is...
 
DR,

Are you refering to varying the actual frequency to the 3phase motor,
or the frequency of the pulses imposed on a 60Hz,
which would be a pulse modulated 60Hz voltage?

Since VFD signals are used widely, for slow down,
and since I don't recall any problems in reducing the motor speed,
I am wondering if we are talking about the same thing.

I am also trying to match my terms with standard ones,
so that communication is better.
Just a semantic question.

...
 
weressl said:
The ASD, as per the IEEE decision, is to be used to identify electronic control products that vary the speed and torque characteristics of AC motors by means of adjusting frequency and voltage supply.
Click to expand...
Doesn't ASD mean Adjustable Speed Drive?
The I triple E definition seems to be specifically VFDs and exclude every other type of ASD.
Not good.
 
glene77is said:
DR,

Are you refering to varying the actual frequency to the 3phase motor,
or the frequency of the pulses imposed on a 60Hz,
which would be a pulse modulated 60Hz voltage?

Since VFD signals are used widely, for slow down,
and since I don't recall any problems in reducing the motor speed,
I am wondering if we are talking about the same thing.

I am also trying to match my terms with standard ones,
so that communication is better.
Just a semantic question.

...
Click to expand...

This thread's original post is VFD (frequency), the cycles will be controlled.
 
glene77is said:
DR,

Are you refering to varying the actual frequency to the 3phase motor,
or the frequency of the pulses imposed on a 60Hz,
which would be a pulse modulated 60Hz voltage?

Since VFD signals are used widely, for slow down,
and since I don't recall any problems in reducing the motor speed,
I am wondering if we are talking about the same thing.

I am also trying to match my terms with standard ones,
so that communication is better.
Just a semantic question.

...
Click to expand...

Pulse width modulation. But, then it isn't 60 Hz anymore.
 
tryinghard said:
I?m involved with a project that has two 5hp 3ph pumps that are currently circuited with #10 THHN cu building wire, running about 50? from source to termination box. Apparently these pumps are too fast so rather than downsize the pump drives are being installed.

The existing pump motor circuits share a 1 ?? conduit with two TP?s (4 #12?s, a pair for each pump). An installer is concerned that the pump circuits should be replace with shielded cable with the use of the drives.

I really don?t understand how controlling the frequency can cause problems. Is this really necessary, can these operate trouble-free without using shielded cable for the pump circuits?
Click to expand...
My two cents FWIW - but bear in mind I'm from planet UK.
I've been playing around with VSDs for about 40 years and in particular, VFDs for about the last 25 years.
Starting with your point about controlling the frequency.
The problem isn't with the fundamental frequency i.e. whether you run the motor at 40Hz or 55Hz. It arises from the pulse width modulated nature of the waveform. That has a switching frequency that my be 10kHz or higher, and worse, a switching edge rise time that may be 1us or less which implies frequency components of 1MHz or above.
In short, it's a pretty good source of continuous noise.
For that reason, we have always run separate power cables for each VFD and had signal cables segregated from power cables both electrically and physically.
The power cables are generally steel wire armoured with the armouring providing EMC shielding. I don't ever recall conduit being used but if it is steel maybe it would be as effective as the armoured cable. The one thing I wouldn't do is to run both motor cables in the same conduit.
 
drbond24 said:
Pulse width modulation. But, then it isn't 60 Hz anymore.
Click to expand...

Yes it is, but it can be lower than 60Hz and higher than 60Hz.

What your are thinking of is the carrier frequency.

The fundamental frequency remains based on the 60Hz. The carrier frequency divides each half of positive and negative segment of the sine-wave and breaks it up to full voltage pulses of varying widht(time duration) to synthetize the sinewave. The pulses width at the crossover start out very short and gradually increase up to the peak of the sine-wave, after which peak the trand reverses. After crossing the zero point again at the end of one half sine-wave the cycle begins with opposite 'polarity' pulses.
 
TryingHard,

As a matter of collecting perspectives
(sometimes differing perspectives),
I present this response.

In another thread in this same topic,
I quote from Boseker, which goes along my experience.

Quote:
Boseker wrote in part of the thread on this topic:
My two cents FWIW - but bear in mind I'm from planet UK.
I've been playing around with VSDs for about 40 years and in particular,
VFDs for about the last 25 years.

Starting with your point about controlling the frequency.
The problem isn't with the fundamental frequency
i.e. whether you run the motor at 40Hz or 55Hz.
It arises from the pulse width modulated nature of the waveform. That has a switching frequency that my be 10kHz or higher, and worse, a switching edge rise time that may be 1us or less which implies frequency components of 1MHz or above.
In short, it's a pretty good source of continuous noise.

For that reason, we have always run separate power cables for each VFD
and had signal cables segregated from power cables both electrically and physically.
The power cables are generally steel wire
armoured with the armouring providing EMC shielding.
I don't ever recall conduit being used
but if it is steel maybe it would be as effective as the armoured cable.
The one thing I wouldn't do is to run both motor cables in the same conduit.

EndQuote:

I am sure these are not the last word on this subject,
as this group of electricians and engineers has a wealth of experience,
and sometimes different ways of saying the same thing.

...
 
weressl said:
Yes it is, but it can be lower than 60Hz and higher than 60Hz.
Click to expand...

Frequencies lower than 60 Hz and frequencies higher than 60 Hz have something in common; they aren't 60 Hz. Isn't that what I said? :D

weressl said:
The fundamental frequency remains based on the 60Hz. The carrier frequency divides each half of positive and negative segment of the sine-wave and breaks it up to full voltage pulses of varying widht(time duration) to synthetize the sinewave. The pulses width at the crossover start out very short and gradually increase up to the peak of the sine-wave, after which peak the trand reverses. After crossing the zero point again at the end of one half sine-wave the cycle begins with opposite 'polarity' pulses.
Click to expand...

I summarize all of that as "it uses DC to fake AC." Would that be fairly correct?
 
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