Baldor Standard-E + 2Hp VFD issues/questions

Been a wile since I posted here, But I am back and its great!
I recently landed a new free Baldor Standard E 3 ph motor to use with my grizzly mill ( on order now ).

Also just bought a 2HP single phase input 3 phase output VFD for a good price made by Bedford.

Any way, I been tinkering with it and testing it out, lots of options but one really confuses me.
Setup ( Motor = 4 pole 1740RPM 60hz 230V FLA = 5.6 amps 84% efficient )
Bedford VFD 2HP ( mostly original setup as manual, Other then sine wave carrier is at 15KHz - I don't think that effects any thing other then that annoying pitch I hear at slow speeds.

If any one is curious please take a peek, PDF format!
http://members.shaw.ca/H2O2/images/B801 Bedford user manual.pdf

Ok so I start her up and run it to the RPm range of about 1500RPM or so......Grab the shaft with glove and clamp down, I can literally stop the motor, then it doesn't want to come back up to speed, Is this motor not capable of being fed by a VFD?
I have the VFD setting on constant torque, but I am wondering what is going on exactly.......I know know much about VFD's so if some one takes a peek through the PDF and suggests some settings I am all yours!

I bought 2 VFD's to go onto my lathe and mill, basically both motors are identical, other then the FLA, one is 5.6 the other is 6, So I would really like this working.

Mind you I wont be turning the Hz down so far for the torque to be non existent, since the mill and lathe both have belt or gear adjustments - So if I want to run fast Ill put then mill or lathe down into the basement for RPM on the machine, then fine tune with the VFD........Right?

Thanks every one!

First off, putting the carrier freq. up to 15khz does more than just get rid of the whine. You likely have to de-rate the VFD as well because the switching losses are a lot higher at anything above about 8kHz.

From the manual for the VFD: "F-18 Carrier wave frequency selection.
Effective power stage switching frequency inverter. Improvements in
acoustic noise and output current waveform occur with increasing
switching frequency at the expense of increased losses within the drive"

You also increase the losses in the motor, so it will run hotter. If you don't load it fully, may not be an issue. If you run it near full load a lot, you will shorten the motor life.

Secondly, it sounds as though you made a very common mistake. Your motor is likely rated for 230/460V. Assuming you are feeding the VFD with 240V, if you accidentally strapped the motor connections for a 460V supply, you will have a LOT less torque. It may still spin at the right speed, but will easily stall and have trouble recovering. Sound familiar? Double check your motor connection pattern in the peckerhead.

Jraef said:

First off, putting the carrier freq. up to 15khz does more than just get rid of the whine. You likely have to de-rate the VFD

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Whether or not you have to derate the VFD is a design issue. The manual should tell you if you have to or not. I have had some VFD's that I did not have to derate. Others I had to derate when the carrier was above 12kc. Still others said that I had to derate only under extreme conditions and at a carrier of 15kc.

If you VFD faults with an overtemp, then drop the carrier frequency to see if that helps.

JRAEF, you are the first person to actually mention the wireing issue, and that solved it ( THANKS A BUNCH ) "excited happy dance"
The motor is SUPER strong now, cant even flinch the speed when running 90Hz.

So my issues are solved, can you go in more depth on how I de rate my VFD with the carrier wave form adjusted to 12-16KHZ?
Where did I degrade it to or how does it work?!

Also........
OK technical questions
Slip compensation
DC injection start and stop
voltage boost ( % max output voltage )

And any thing else the PDF might have for me thats useful, Thanks!

Since the manual makes no mention of derating the drive then there is no concern and no derating is needed.

Derating means you have to lower the VFD's output current rating. If the VFD requires derating due to high carrier frequency, the manual should provide derating factors. For example, at 15 kHz it may say to derate to 90%. So if the VFD's normal output current rating is 10 amps, you would only be able to load it to 9 amps at 15 kHz.

Slip compensation allows the VFD to counteract the motor slip. A typical 1800 RPM motor only spins at about 1750 RPM when fully loaded. This difference is called "slip". The VFD can increase the output frequency a little bit to compensate for this.

DC Braking is where the VFD injects DC voltage/current into the motor to either help stop the motor faster, or keep it stopped, or both. There should be settings that adjust the amount of DC voltage and the duration. Be careful though, as too much DC for too long can damage AC motors. When trying to stop motors quickly, oftentimes Dynamic or Regenerative Braking works better than DC braking, but there is a cost for this, as you typically have to purchase an external resistor. When you try to slow a motor down faster than it will coast on its own, it becomes a generator and will regenerate power back into the VFD (and onto its DC bus), which must be dissipated otherwise the VFD will end up tripping due to high DC bus voltage. Adding the resistor gives the energy somewhere to go so the VFD doesn't trip out.

Without any other info to go on, I'm assuming the voltage boost is for generating extra starting torque. Regular V/Hz VFDs output a fixed V/Hz ratio that matches the motor (i.e. 230V / 60Hz = 3.8 V/Hz). The VFD will always output this ratio to the motor, and it will generate pretty good torque across the whole speed range. But at the very low end, better torque can be achieved with a higher V/Hz ratio, so the voltage boost setting allows this. Vector drives, on the other hand, continuously adjust the V/Hz ratio to always generate the maximum amount of torque at any speed.

John

Thanks for the explnations. I dont see a derate on my manual, I assume it doesnt........

How can I calculate slip or what should I adjust the setting to?

I have it on dynamic breaking, it has a big resistor built in and I can stop the dree spinning motor from 2000RPM to zero in less then 1 second, Mind you its got nothing connected to it YET.

Do you recomend I leave it out for stopping the motor, when I turned it on I noticed it held the motor in place after it stopped ( for the duration I set the setting to ) in this case it was 10 seconds.

What about starting it, Is it a good idea if its under heavy loud to inject some DC into its veins?

Right I understand the boost option, Straight forward now!

Thanks for the help!

any one?

thanks

There are two kinds of dynamic braking. One is DC braking and the other is AC. AC braking is also called deceleration time. I would leave the DC braking at it's factory default until you actually get the VFD installed on the machine and have run it a while.

In your application there is no reason to apply the DC brake before starting.

If it were me I would shut off DC braking altogether (which seems to be the factory default for your Bedford drive). DC braking can suck up the power thus raising your electric bill.

What did you pay for that Chinese VFD and who did you order it from?

Thanks for the information.

Well I am not going to be reselling these drives to the public, Thats how cheap it was haha.
I am going to be offering these drives in the 180-190$ price range, with potential free shipping with in North America.

Thanks!

VooDooMan said:

Thanks for the information.

Well I am not going to be reselling these drives to the public, Thats how cheap it was haha.
I am going to be offering these drives in the 180-190$ price range, with potential free shipping with in North America.

Thanks!

Click to expand...

You have some pretty stiff competition. A Teco/Westinghouse 2hp FM50 with a 2 year warranty is $145.00 and shipping a drive is cheap because it is so light. There are cheaper drives out there but the two year warranty is what keeps me buying TECO drives. The other part is that Westinghouse isn't likely to go out of business anytime soon.

VooDooMan said:

Thanks for the explnations. I dont see a derate on my manual, I assume it doesnt........

Click to expand...

You know the old saying about the word ass-u-me don't you?

IMHO, all VFD manuals should say very specifically whether or not a drive needs to be derated for higher carrier frequencies. There is no getting around the fact that it creates more switching losses and therefore more heat. Since one of the main controllable costs in a VFD design is the heat sink, I find it hard to believe that any VFD designed to be low cost is going to be over designed in that area. Your drive's manual does have a statement, ambiguous though it is, and if your drive fries they will likely point to it as a reason to stiff you for a replacement.

My take is that cheaper VFDs just don't bother to tell you one way or the other because it can appear to be a weakness to someone who does not understand the issue. I'm not saying that people shouldn't buy cheap VFDs, I'm just pointing out that the lack of information should not be taken as tacit approval either.

He can gauge just how hot the VFD it is getting by listening to the fan. If the VFD fan never shuts off when the drive is in use, then it is time to be concerned. If the fan cycles on and off, then things are OK.

I was under the impression that most, if not all, small VFDs like we are talking about here have fans that run whenever power is applied (I know AC Tech is that way). Like Jraef says about heatsinks, I think the same would apply to thermostat-controlled fans.

However, I know that some VFDs take the carrier frequency into account in the motor overload algorithm to at least protect the VFD if the load is too high for the carrier frequency. Don't know if this one does or not...but after looking at the manual I would doubt it, and would agree with Jraef that they would use it as a reason to not cover a failure under warranty.

John

The Bedford VFD is like the Teco 7300 in that it has a thermostatically controlled fan. The Teco FM50 fan runs whenever the VFD is operating.

Warranty for a Bedford? I cannot even find one for sale let alone find any info about the warranty.

The only issue here is whether of not the heat sink is big enough for the added load a high carrier frequency brings. Overload and alogorithims has nothing to do with it.

The only issue here is whether of not the heat sink is big enough for the added load a high carrier frequency brings. Overload and alogorithims has nothing to do with it.

Click to expand...

All I'm saying is that some VFDs (such as AC Tech) will do the derating for you automatically so that the VFD protects itself when operating at high carrier. For example, if operation at a higher carrier requires derating to 90% (as in my example above), the motor overload algorithm will scale down its threshold by that amount. Then if you try to operate at 100% load, the VFD actually sees it as 111% and will eventually trip out to protect itself.

Maybe that's not the case with this particular VFD (but how do we know since the manual is so poorly written/translated?), but that doesn't mean my comments should be summarily dismissed as having "nothing to do with it".

John

J Lauffer said:

All I'm saying is that some VFDs (such as AC Tech) will do the derating for you automatically
John

Click to expand...

I was uninformed about the AC Tech drives and how they deal with high carrier frequencies. I had no idea that they set the overload limits lower. I don't agree with that design philosophy but there it is.





.

Curious, do you disagree with having to derate at all for high carrier, or that some VFDs derate for you?

I could understand disagreeing with having to derate at all (in my opinion if the VFD can operate at 16 kHz then it should be thermally designed to handle it w/o derating), but if derating is required, what's wrong with the VFD taking care of it automatically (as long as it is clearly stated in the manual of course)?

John

Maybe I misunderstood the manual, but the SMVector documentation shows two derating tables:

NEMA 1:
8 kHz derate to 92%
10 kHz derate to 84%

NEMA 4x:
6 kHz derate to 92%
8 kHz derate to 84%
10 kHz derate to 76%

Both the NEMA 1 & the NEMA 4x automatic shift to 4 kHz at 120% load to avoid derating.

http://www.actech.com/documents/techlib/SV01D-e1.pdf

J Lauffer said:

Curious, do you disagree with having to derate at all for high carrier, or that some VFDs derate for you?

I could understand disagreeing with having to derate at all (in my opinion if the VFD can operate at 16 kHz then it should be thermally designed to handle it w/o derating), but if derating is required, what's wrong with the VFD taking care of it automatically (as long as it is clearly stated in the manual of course)?

John

Click to expand...

John,

I don't think my opinion about auto-derating matters at all since it is:

1 - used by a mfgr of VFDs that I have no intention of ever buying.
2 - it is a fixed "feature" that cannot be changed

Since it is pointless I would rather not.