vfd question
 

I am in the market for a VFD. The motor it is driving is a 10HP Baldor
3 phase. I have single phase power (100amp service). Talking to a
recommended online supplier they suggest a 20HP VFD, which from what I
have read sounds reasonable. My question is in what brand to get.
They have 20HP Westinghouse/Teco for about $1200, and a surplus 25HP
WEG for $850. I'd rather spend more dough if the WEG gets questionable
results. Thanks for the input!

wrote in message
ups.com...
I am in the market for a VFD. The motor it is driving is a 10HP Baldor
3 phase. I have single phase power (100amp service). Talking to a
recommended online supplier they suggest a 20HP VFD, which from what I
have read sounds reasonable. My question is in what brand to get.
They have 20HP Westinghouse/Teco for about $1200, and a surplus 25HP
WEG for $850. I'd rather spend more dough if the WEG gets questionable
results. Thanks for the input!

I thought the normal rating was something like 150%. Thus a VFD rated for
15HP would be safe for a 10HP motor. I might be wrong on that. Save for
that I would look at exactly what the manufacture specs dictate. If the VFD
is rated to convert single phase to 3 phase, the rating will be there as
well. 10HP to a 20HP VFD is a big jump in price.

Another thing to look at is braking. Does the unit provide braking, or do
you care if the VFD can brake the motor. Other than that a lot of the more
expensive VFDs have fancy controls, user interfaces, different inputs, etc,
that may or may not be needed in your application.

For what it is worth VFDs are plentiful on ebay. I picked up a $1300
Siemens unit for ~$150. It was a 3 phase only VFD though. I do think the
single phase to 3 phase converters do go for more, for obvious reasons.

Otherwise good luck.


--
Chris

If you can read this, thank a teacher. If it is in English, thank a
soldier. If it is in ebonics, thank your Congressman.

Chris wrote:

For what it is worth VFDs are plentiful on ebay. I picked up a $1300
Siemens unit for ~$150. It was a 3 phase only VFD though. I do think the
single phase to 3 phase converters do go for more, for obvious reasons.
I have two "3 phase only" VFDs in my shop running on single phase power.
I have a 1 Hp Magnetek GPD-333 (made by Yaskawa) running my 1 Hp.
Bridgeport with no problem. Had I known about the derating at the time,
I might have gone for a larger unit, but it seems to work fine.

I have a 15 KVA Toshiba runing a 7.5 Hp lathe, and of course it works
fine, too.

Jon

Make sure the VFD of choice will run on single-phase. Some have phase loss
detection which shuts down the unit if a phase goes down.

Randy


wrote in message
ups.com...
I am in the market for a VFD. The motor it is driving is a 10HP Baldor
3 phase. I have single phase power (100amp service). Talking to a
recommended online supplier they suggest a 20HP VFD, which from what I
have read sounds reasonable. My question is in what brand to get.
They have 20HP Westinghouse/Teco for about $1200, and a surplus 25HP
WEG for $850. I'd rather spend more dough if the WEG gets questionable
results. Thanks for the input!

"R. O'Brian" wrote in message
news:81kUe.22811$hp.4649@lakeread08...
Make sure the VFD of choice will run on single-phase. Some have phase
loss
detection which shuts down the unit if a phase goes down.

Randy

Is that a parameter that can be changed through programming?

wrote in message
ups.com...
I am in the market for a VFD. The motor it is driving is a 10HP Baldor
3 phase. I have single phase power (100amp service). Talking to a
recommended online supplier they suggest a 20HP VFD, which from what I
have read sounds reasonable. My question is in what brand to get.
They have 20HP Westinghouse/Teco for about $1200, and a surplus 25HP
WEG for $850. I'd rather spend more dough if the WEG gets questionable
results. Thanks for the input!

According to ATP* :

"R. O'Brian" wrote in message
news:81kUe.22811$hp.4649@lakeread08...
Make sure the VFD of choice will run on single-phase. Some have phase
loss
detection which shuts down the unit if a phase goes down.

[ ... ]

Is that a parameter that can be changed through programming?

Probably not -- but you can often fool it by strapping the one
unused phase to the nearest of the other two. It is not checking
whether it is different from both of the others, but rather whether
there is something there -- so it can safely shut down when being used
at full rating if one phase of the power feed is lost.

Enjoy,
DoN.

--
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---

In article ,
says...

"R. O'Brian" wrote in message
news:81kUe.22811$hp.4649@lakeread08...
Make sure the VFD of choice will run on single-phase. Some have phase
loss
detection which shuts down the unit if a phase goes down.

Randy

Is that a parameter that can be changed through programming?

It's a pretty unusual feature on small (10-20HP?) VFDs. In
20+ years of building and working around industrial
machinery I've never actually run across a small VFD that
wouldn't run on single phase.

Ned Simmons

"Ned Simmons" wrote in message
...
In article ,
says...

"R. O'Brian" wrote in message
news:81kUe.22811$hp.4649@lakeread08...
Make sure the VFD of choice will run on single-phase. Some have phase
loss
detection which shuts down the unit if a phase goes down.

Randy

Is that a parameter that can be changed through programming?

It's a pretty unusual feature on small (10-20HP?) VFDs. In
20+ years of building and working around industrial
machinery I've never actually run across a small VFD that
wouldn't run on single phase.

Ned Simmons

I have a 25 HP and a 45 HP VFD for future projects. They are the ones I'm
concerned about. I'll try Don's suggestion if there's a problem.

"Ned Simmons" wrote in message
...
In article ,
says...

"R. O'Brian" wrote in message
news:81kUe.22811$hp.4649@lakeread08...
Make sure the VFD of choice will run on single-phase. Some have phase
loss
detection which shuts down the unit if a phase goes down.

Randy

Is that a parameter that can be changed through programming?

It's a pretty unusual feature on small (10-20HP?) VFDs. In
20+ years of building and working around industrial
machinery I've never actually run across a small VFD that
wouldn't run on single phase.

Ned Simmons

Ned,
Why are small of the smaller VFDs rated for single phase? I do know that the
used VFDs that are rated for single phase seem to be going for a premium.
Are you saying that any smaller VFD will convert single phase to 3?


--
Chris

If you can read this, thank a teacher. If it is in English, thank a
soldier. If it is in ebonics, thank your Congressman.

Ned sez:

"It's a pretty unusual feature on small (10-20HP?) VFDs. In
20+ years of building and working around industrial
machinery I've never actually run across a small VFD that
wouldn't run on single phase."

So, see Ned, how you've cut through tons of technical BS and gotten right
through to the central (and simple) theme of the subject at hand. Hey! No
reading of spec sheets for you - you made an assumption and acted on it. It
sorta stands to reason if a 3-phase motor can run on single-phase juice then
so can a VFD. So simple! We doesn't need no stinkin' spec sheets!

We have an award for folks like you. It is offered to those that somehow
cheat "Darwin" and continue on to unheralded fame. It gives me great
pleasure to award you the first ever "IGGY". Picture it! Cute little
statue . . . somewhat grotesque though, of a little idiot standing with one
foot on his tongue and the other on his dick.

Bob Swinney







"Ned Simmons" wrote in message
...
In article ,
says...

"R. O'Brian" wrote in message
news:81kUe.22811$hp.4649@lakeread08...
Make sure the VFD of choice will run on single-phase. Some have phase
loss
detection which shuts down the unit if a phase goes down.

Randy

Is that a parameter that can be changed through programming?


Ned Simmons

On Sun, 11 Sep 2005 01:09:51 -0400, Ned Simmons
wrote:

In article ,
says...

"R. O'Brian" wrote in message
news:81kUe.22811$hp.4649@lakeread08...
Make sure the VFD of choice will run on single-phase. Some have phase
loss
detection which shuts down the unit if a phase goes down.

Randy

Is that a parameter that can be changed through programming?

It's a pretty unusual feature on small (10-20HP?) VFDs. In
20+ years of building and working around industrial
machinery I've never actually run across a small VFD that
wouldn't run on single phase.

Ned Simmons

Don't all VFD's work by converting DC to synthesized 3-phase AC?

With rectified 3-phase there is no need to store energy because
full-wave rectified AC never goes below 86.6% of peak line voltage.
With rectified single-phase, some capacitive storage is necessary so
there is always DC available to synthesize all three phases.

So, it would seem that any VFD should be able to run on single-phase
if sufficient capacitive storage is present.

In article ,
says...
On Sun, 11 Sep 2005 01:09:51 -0400, Ned Simmons
wrote:

In article ,
says...

"R. O'Brian" wrote in message
news:81kUe.22811$hp.4649@lakeread08...
Make sure the VFD of choice will run on single-phase. Some have phase
loss
detection which shuts down the unit if a phase goes down.

Randy

Is that a parameter that can be changed through programming?

It's a pretty unusual feature on small (10-20HP?) VFDs. In
20+ years of building and working around industrial
machinery I've never actually run across a small VFD that
wouldn't run on single phase.

Ned Simmons

Don't all VFD's work by converting DC to synthesized 3-phase AC?

All that I'm familiar with, yes.


With rectified 3-phase there is no need to store energy because
full-wave rectified AC never goes below 86.6% of peak line voltage.
With rectified single-phase, some capacitive storage is necessary so
there is always DC available to synthesize all three phases.

The capacitance also serves to absorb energy when the drive
is decelerating the motor. Many (all?) VFDs will disable
the motor if the bus voltage goes out of range. Some can be
configured to display the bus voltage, which can be useful
when setting the accel/decel parameters and for determining
if a braking resistor may be required.


So, it would seem that any VFD should be able to run on single-phase
if sufficient capacitive storage is present.


Which is why I referred to lost phase detection as a
"feature". If a drive can detect a lost phase condition
then it seems to me that capability is intentional, not a
necessary consequence of the design.

Ned Simmons

In article ,
says...


Ned,
Why are small of the smaller VFDs rated for single phase? I do know that the
used VFDs that are rated for single phase seem to be going for a premium.
Are you saying that any smaller VFD will convert single phase to 3?


Did you mean to say "Why are *some* of the smaller VFDs
rated for single phase?"

I can only speculate why some mfrs don't put single phase
ratings in their literature - perhaps they perceive it as a
small and potentially troublesome market. If you actually
ask the applications guys they'll give you a
recommendation, which usually involves derating the drive
by some factor, most often to 1/2 to 2/3 of it's three
phase rating. I personally think that derating a drive that
sees light and intermittent use by 1/2 is very
conservative.

Ned Simmons