# commercial vfd's (ABB) - tweakable?



## major (Apr 4, 2008)

boekel said:


> Does anyone have experience with commercial vfd's regarding driving them with lower voltage DC than designed to use, and / or lower AC voltage / Hz?


Hi bo,

They typically have a LV point at which a fault will trip. This may be a settable parameter going as low as maybe 60% of the normal DC bus voltage. It was not possible to hack the software to go lower, but found a way to do it in the hardware sensing circuit. Of course you must derate when going to lower voltage and adjust the motor tuning appropriately. This would apply to either a DC supply or AC supply.

The lower frequency AC supply may require some alteration in the input capacitor filter.

Anytime you reduce the input voltage to the VFD you proportionally reduce the maximum output voltage. This in turn reduces the base frequency/RPM for the motor and peak power. Motors should be fine with it if actively cooled.

I would think that your small motor would tolerate higher voltage and frequency. It would increase base frequency/RPM and peak power. The liquid cooling can only remove so much heat, so continuous power may stay about the same or actually decrease at high speed.

Regards,

major


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## DIYguy (Sep 18, 2008)

boekel said:


> I've also become the proud owner of a UQM Powerphase 150 set,



Kewl. Did you buy the one from Ebay that was listed a day or two ago?? If so, it's apparently a "new" unit....

edit. . . nope Powerphase 150 is still on fleabay.... http://www.ebay.com/itm/220973902558?ssPageName=STRK:MESELX:IT#ht_954wt_11 30


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## boekel (Nov 10, 2010)

major said:


> Hi bo,
> 
> They typically have a LV point at which a fault will trip. This may be a settable parameter going as low as maybe 60% of the normal DC bus voltage. It was not possible to hack the software to go lower, but found a way to do it in the hardware sensing circuit. Of course you must derate when going to lower voltage and adjust the motor tuning appropriately. This would apply to either a DC supply or AC supply.


 Did you do the hw trick on an ABB vfd? I'm planning on buying a small one from the same series of the big machine to test things.


> The lower frequency AC supply may require some alteration in the input capacitor filter.


 Ok, will ask advice from pro's when necessary.


> Anytime you reduce the input voltage to the VFD you proportionally reduce the maximum output voltage. This in turn reduces the base frequency/RPM for the motor and peak power. Motors should be fine with it if actively cooled.


 Yes I will keep an eye on Amp's used.


> I would think that your small motor would tolerate higher voltage and frequency. It would increase base frequency/RPM and peak power. The liquid cooling can only remove so much heat, so continuous power may stay about the same or actually decrease at high speed.


I don't even know yet what frequency it needs 



DIYguy said:


> Kewl. Did you buy the one from Ebay that was listed a day or two ago?? If so, it's apparently a "new" unit....


 Mine comes from an auction in the Netherlands of a company that went out of business, Will certainly sell it for the amount the person on Ebay asks for it 

At the moment the UQM system is still in the back of my car...and my car broke down while collecting it!
When I get it back I'll make a separate topic about it, will test it on 11kW power supply


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## major (Apr 4, 2008)

boekel said:


> Did you do the hw trick on an ABB vfd?


No, an old version Yaskawa.


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## subcooledheatpump (Mar 5, 2012)

Hi Boekel

Are you that guy on youtube "dboekel" with the awesome diesel electric boat? from your first post and your username it sounds like it must be you. 

Anyway, I understand your reasoning for trying to run a VFD with a lower voltage/frequency at the input. However, running at a lower voltage might cause the internal power supply greater stress. It of course would also make setting off the low voltage lockout protection even eaiser. You run a risk of the internal power supply shutting off and causing the IGBT gate drivers to lose power and lose control of the IGBTs during switching 

Just my thoughts.

I like the boat though any chance you'll make more videos of it?


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## boekel (Nov 10, 2010)

subcooledheatpump said:


> Hi Boekel
> 
> Are you that guy on youtube "dboekel" with the awesome diesel electric boat? from your first post and your username it sounds like it must be you.


Guilty...


> Anyway, I understand your reasoning for trying to run a VFD with a lower voltage/frequency at the input. However, running at a lower voltage might cause the internal power supply greater stress. It of course would also make setting off the low voltage lockout protection even eaiser. You run a risk of the internal power supply shutting off and causing the IGBT gate drivers to lose power and lose control of the IGBTs during switching


I did accidentally throttle down the generator without turning of the power, vdf was still happy until engaging fwd, than it gave 'DC-bus low' error...


> I like the boat though any chance you'll make more videos of it?


I don't know (yet) how to make a separate feed on youtube, so here are some links:
http://www.youtube.com/watch?v=_z8ALiBgUZM
http://www.youtube.com/watch?v=iM9KMC3aKIs
http://www.youtube.com/watch?v=v_nC-ebZdtU
http://www.youtube.com/watch?v=dPGMGF9LKis
http://www.youtube.com/watch?v=ve5ROtHNzaA
http://www.youtube.com/watch?v=8D1e3zzNffE
http://www.youtube.com/watch?v=CDaaEQC8fk4
http://www.youtube.com/watch?v=tMumFR3YQ0c
http://www.youtube.com/watch?v=5Ee7ddZk5hc
http://www.youtube.com/watch?v=k2WfbZglXu8
http://www.youtube.com/watch?v=OtWGlbjm57Y
http://www.youtube.com/watch?v=Olo1AutO_1E
http://www.youtube.com/watch?v=pO0yj2N8wuw
http://www.youtube.com/watch?v=rkdlHNVe0SY
http://www.youtube.com/watch?v=4sIZ8SLx2QU
http://www.youtube.com/watch?v=c696hWnXj7M
http://www.youtube.com/watch?v=2ZSenSCv8zI
http://www.youtube.com/watch?v=awuhe82_P0I
http://www.youtube.com/watch?v=BGIH_5SjOrQ
http://www.youtube.com/watch?v=b1tY2wrMSQc


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## boekel (Nov 10, 2010)

A simple calculation on lead-acid (OPzS) traction cells:


```
1,65   1,75   2,1    2,4    2,5
no.of  heavy  normal rest   normal equalize
cells  discrg discrg        carge  charge
210    347    368    441    504    525
215    355    376    452    516    538
220    363    385    462    528    550
225    371    394    473    540    563
230    380    403    483    552    575
235    388    411    494    564    588
240    396    420    504    576    600
245    404    429    515    588    613
250    413    438    525    600    625
260    429    455    546    624    650
```
Since 'normal' DC-bus voltage (@380v-AC) is about 540 volts, 225 cells seems like about the right number for charging via the vfd, while needing an external charger to reach equalizing voltage (a 'forklift battery' needs to gass while charging to mix the acid, otherwise heavier fluid sits at the bottom of the cell)

Under heavy load a 215 cell pack will reach about 355 volts...a lot less than the normal DC-bus voltage...that's why I need to find out the limits of my vfd's

On the other hand:
Lower DC-bus means lower max rpm on my motor, so if I want full rpm (1000) I'll need a minimal DC of ???

So...can I prevent needing a separate charger for max. charge voltage? By turning up the rpm on the gen-set to get towards max AC-voltage and hertz of the vfd's input I can up the DC-voltage, hopefully towards the needed charging voltage while maintaining the needed DC-voltage under load while sailing on battery's.

A long time stands between now and purchasing a big 200+ cell's battery pack, so I want to test drive with a smaller vfd and a battery pack from a discharged (uhhh..) industrial UPS system.


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## boekel (Nov 10, 2010)

Lithium might still be interesting for a 'small' pack because of the higher allowed discharge current, makes charging and discharging voltges a little easyer, while adding the need for a big bms system.


```
cells  disch  rest   charge
130    390    468    540
135    405    486    560
140    420    504    581
145    435    522    602
150    450    540    623
155    465    558    643
```
On a relatively big heavy boat like mine you don't need much power to keep moving, 15 kW is enough for quite fast cruising, you do want power for stopping and maneuvering, 65 kW does it for now, when finished converting (and doubling the weight to about 80 tonnes) 100-150 kW would be nice


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## boekel (Nov 10, 2010)

---update---
I did the rtfm thing 
ABB ACS800 controller, 400 volts version:
Minimum DC voltage: 307 V
Maximum DC voltage: 728 v

That's a nice big bandwidth wich gives lots of possible pack-voltages.

215 - 220 cell lead-acid battery or about 130 cell lithium would fit nicely.
To get a higher cell battery to charge via the vfd would need a higher AC voltage, witch might be possible by tweaking the gen-set.


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