Single Phase Variable Frequency Drive 2

[WoodrowJWeen]

Does anyone know who makes a VFD for a 1/2 HP, 5V, 1PH fan motor? This needs to be in a NEMA 1 enclosure. We can't just use a simple wall box fan speed controller because the speed will be controlled automatically by a differential pressure monitor to accomodate filter loading.

 

[buzzp]

5V?

 

[yrahul]

A 5 volt AC motor? 0.5 HP at 5 volts? Could you confirm the values? Are you sure that it's not a DC motor?

Putting aside my confusions about the voltage and power values, you can always use a three-phase drive with a single phase motor. Just use two of the three terminals. The 3ph drive has to be of right rating, and that's where I'm totally at a loss with your spec.

Yeasir Rahul

Principal, VoltSmith Technologies

http://www.voltsmith.com

 

[WoodrowJWeen]

Doh...it was 115 volts not 5 volts.

 

[btrueblood]

Literally dozens of suppliers of that class of VFD. Search on google. Check

http://www.grainger.com

 

[buzzp]

Allen Bradley is one of them (maybe its ABB or both, cant recall). There is no reason you would need to use a 3phase drive. I have never done this and on the surface, it seems like a bad idea.
I don't know if these little drives have optional speed control through an analog signal or not but I do know their are several 1 phase drive mfgs.

 

[jraef]

ALL of the above posts are INCORRECT! The OP stated that he has a 1 phase MOTOR!

1) You CANNOT just hook up 2 of the 3 outputs of a 3 phase drive to a 1 phase motor. It WILL NOT WORK! The VFD would trip out on Output Phase Loss at the very least, if you are lucky! And if you hook up the "3rd wire" (green one) to 3rd terminal of the VFD (as I have seen too many people do), the VFD will let out it's magic smoke.

2) There are very few manufacturers of VFDs for 1 phase motors, and NONE of the ones mentioned above have a product for that application. The only one I have seen is from Anacon Systems,

http://www.anaconsystems.com/text/eagle1.html

but be aware, it only works on a selected FEW types of 1 phase motors. The problem is that you cannot use VFDs on any type of 1 phase motor that uses capacitors in the starting or running circuit. Unfortunately that makes up about 75% of the commonly used 1 phase motors in the HP size you are looking for. VFDs for 1 phase motors basically only work on shaded pole or split-phase motors. It is possible that your fan motor is one of these, so you may be in luck, but please be very careful about what you ask your vendor for. The mistakes made in the above posts are VERY COMMON among vendors, but result in blown drives and/or disappointed users.

An alternative is to replace the motor with a 230V 3 phase version that fits into the same mounting config. Then there are PLENTY of VFD manufacturers who now sell drives that will directly convert 115V 1 phase to 230V 3 phse, without needing to use a step-up transformer.

"Venditori de oleum-vipera non vigere excordis populi"

 

[buzzp]

Well I know ABB or Allen Bradley have at least a 3HP 115 Volt model. I could be wrong on the name.

I never said a 3phase drive could be used either. SO no not all of the posts are wrong. I agree with you item #1 and parts of #2.
In fact, your wrong about no one offering these, see the links below.
Here is a link to a 230V single phase 1/2 HP drive. Thought they had 115Volt but might of been wrong on that.

http://raise.rockwellautomation.com...14&TID=B160CFG&onKil=http://www.ab.com/drives

Here is another link to a single phase 100V drive.

http://search.abb.com/library/ABBLi...anguageCode=en&DocumentPartID=1&Action=Launch

 

[buzzp]

Ignore those links. I read to fast. I will try to find some 115V drives.

 

[jraef]

buzzp,
No disrepect (I know you are usually more careful and thoughtful in your responses), but read those data sheets again. You made the same common mistake I was referring to above. Those are both some of the ones that are 115V input, but 230V 3 phase output as I mentioned. He CANNOT use them on a 115V 1 phase motor. Neither AB nor ABB offer a VFD for a 115V 1 phase MOTOR.

"Venditori de oleum-vipera non vigere excordis populi"

 

[aolalde]

Jraef:
Thanks for the lesson, unfortunately it is frequent to find people (engineers?) making impulsive decisions and regretting later.

 

[ScottyUK]

Hi jraef,

Don't most split phase motors have a centrifugal switch which disengages the starting winding after the motor reaches something approaching rated speed? If you slow down such a motor, the starting winding will engage. These windings are are normally only designed for short-term use, so the winding would probably start to emit its 'magic smoke'.

WoodrowJWeen,

One possibility, since it is a fan load, is to use a phase angle controller typically intended for automated control of heating elements in an industrial process. The fan controllers you mentioned initially produce a similar phase-controlled output, but the units for heating control typically accept a DC control signal rather than having a control knob on the faceplate.

Take heed of the earlier comments about checking the suitability of the motor for use in a variable speed mode, unless you already know that the fan is a controllable type.



----------------------------------

If we learn from our mistakes,
I'm getting a great education!

 

[sbkjaer]

Hello WoodrowJWeen,

Danfoss, a Dansih world-leading company in drives etc, has what you are looking for. Take a look at:

http://lowpowerdrives.danfoss.com/products.htm

best regards
Søren Bækhøj Kjær
M.Sc.E.E.

 

[jraef]

Once again, that proves my point. Yet another example of how easilly mislead people are on this issue. Those Danfoss drives are 3PHASE OUTPUT, he has 1 PHASE MOTOR! They will not work, just like all the others will not work.

Sheesh people, READ ALL OF THE TEXT!

ScottyUK,
Most likely, once the speed drops down and the centrfugal switch kicks in, the caps will cause the VFD transistors to blow before the motor widings. A high tech expensive fuse of sorts ;-} If you click on the link I provided for Anacon, they have a little info-box link that pops up to explain why VFDs will not work on cap start motors. That is relatively new on their site, leading me to believe they were compelled to add it because too many people failed to read the fine print. This is exactly why most VFD manufacturers shy away from making drives for 1 phase motors, it is too easilly misapplied. My company sells one of the versions that take 115V 1 phase and output 230V 3 phase, and we get about 25% of the units returned because users did not read the details and connected them to 1 phase motors, blowing them to smithereens (figuratively of course). If I sound bitter, it is because I am sooooooooo sick of explaining this over and over to people who refuse to read the details!

OK, I am off of my soap box now, returning to more mundane issues at hand.

"Venditori de oleum-vipera non vigere excordis populi"

 

[yrahul]

I was the sloppy engineer that first suggested using a 3ph drive for a 1ph motor in this thread. I was puzzled at the voltage and power values mentioned in the original question; and suggested a wrong solution without thinking much. Fortunately, jraef and buzzp corrected my error.

The phase protection issue (pointed out by jraef) should have crossed my mind. However, the capacitor-start issue may not be that serious if we employ over-design for the power switches. I actually used a 3ph drive in this way for a 1ph, 230v, 1/2HP motor. That was in my sophomore year industrial electronics lab, and the drive was built by me! Sure, it did not have phase-loss protection, and did not mind at all driving that single phase motor. The drive was actually designed for a 2HP, 3ph motor.

Anyway, the best solution for WoodrowJWeen is replacing the 1ph motor with a 3ph one, and empoying an appropriate drive; if replacing is at all possible.

Cheers
Rahul

 

[ScottyUK]

Hi jraef,

I had a look at your link prior to posting - it was actually the motors which have a high resistance, low inductance starting winding with a relatively low resistance, high inductance main winding and no capacitors that I was thinking of. These also use the centrifugal switch arrangement, but you seemed to be specifically talking about cap start motors as being problematic without mentioning that the other type is likely to prove equally troublesome.



----------------------------------

If we learn from our mistakes,
I'm getting a great education!

 

[Skogsgurra]

Hold it guys!

There ARE inverters that can feed single-phase motors.

I have used one to control the speed of a Master Drives fan. The problem was that the fan produces a lot of noise and the customer (paper mill) wanted to be able to reduce the noise temporarily so that he didn't need to use ear protection/intercom to discuss things in front of the inverter.

We had them hook the single-phase Ziehl-Abeg 2800 RPM fan of the main inverter to an NFO inverter, which according to the manufacturer, can take a single-phase load between the output phases. The fan motor is a split phase type with a permanently connected capacitor. Worked well.

 

[jraef]

OK, OK,
I concede that there are SOME drives that will work on SOME 1 phase motors in SOME applications. Of the vast majority of 1 phase motors out there, it will work on 2 types, PSC and Shaded Pole, niether of which are the most common. Both of those are of limited torque capacity, so the applications are limited, probably to fans. Besides the Anacon drive I mentioned as being the only one out there, it appears that SOME 3 phase output VFDs can tolerate having no load connected to ONE leg, i.e. the NFO drive mentioned above (although I found no mention of that in their manual) so they will apparently work on 230V 1 phase PSC or shaded pole motors (do they even make 230V SP motors?). I say apparently because I believe skogs, but I would not have without his endorsement.

All that said, it still does NOT solve his problem of having a 115V 1 phase motor, which would connect Line-to-Neutral, regardless of what type of motor it is. Where is the Neutral going to come from? I don't think you can connect it to the Neutral from the incoming power, because that will have a 60Hz reference from other loads connected at the same time no? I don't know. It is making my head hurt. All I know is my experience of having a lot of our 115V 1 phase input drives come back blown up because the end user ASSumed they could hook it up to a 115V 1 phase motor. With all the caviats, I still say the best bet is to repalce the motor with a 230V 3 phase equivalent.

"Venditori de oleum-vipera non vigere excordis populi"

 

[jraef]

By the way, I apologize for inferring that the link I posted earlier had that pop-up about why they are limited to those motor types. I had read that some time ago and they apparently moved it to a different page, maybe even changed the wording a little. Here is the correct page now.

http://www.anaconsystems.com/text/support.html

Click on the highlighted text (javascript) that says "why?".
They are now taking the position that it is based upon current issues.

Whatever.

"Venditori de oleum-vipera non vigere excordis populi"

 

[Skogsgurra]

You are absolutely right, jraef, that the best thing is to use the right motor in the right place and with the right supply.

But, there are cases when you simply cannot do that. And then it is good to know that there are no absolute no-nos. Like "it's a no-no to connect a drive to a single-phase load".