1-wire single phase to fun 40hp pump with vfd

[winterrules]

We're setting up a pump station/treatment building. The main load will be a 40hp pump with vfd. The other smaller loads in the building are 3 600 watt bulbs for UV and typical lights/receptacles. Can this run off 1-wire single phase?

 

[winterrules]

Sorry about the typo in the subject title.....good first post, huh?

 

[winterrules]

I just found out it's 240V, 200A single phase.

 

[boaterbill]

Yes you probably can, but the pump motor's VFD will need to be configured for the single phase input. The drive will need to be rated for twice the FLA of the motor. This is because only half of the input rectifiers are available to energize the DC bus. So a 120 amp 40 horse VFD will need to be replaced with a 240 amp 80 hp unit to operate it correctly. With that in mind, the 200 amp service is not enough, get more power, 3-phase if you can.

Good luck

 

[CJCPE]

The 200 amp service should be enough just considering the power requirements of a 40 Hp motor, but the total power factor would be low considering the harmonic current with a single phase input to a VFD. In addition, there might be a code problem with sizing the feeder based on the motor Hp rather than the VFD. There is a product that is designed to help with this situation. It is a harmonic filter that includes a phase shifing scheme to allow partial use of all three phases of the VFD input rectifier. I have been told that some drive manufacturers are familiar with this product and have worked out VFD derating factors to use with it. It is the Mirus Lineator 1Q3. I don't have any connection to this company, so I hope I can provide this information without violating the Eng-Tips rules.

http://www.mirusinternational.com/pages/lineator.htm#1q3

 

[BJC]

If your just setting it up change the pump to a 3 phase motor. VFDs with 240 in and 3 phase out are easy to come by.
Run the numbers - it might be cheaper to throw the motor away and start over with a 3 phase motor.

 

[itsmoked]

Welcome winterrules;

That's a great first Subject!
You should see some of the subject screw ups - much worse.

Check with the locals that would supply the VFD. It may well be that the single phase derate is not as draconian as 2X.



Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[jraef]

At that HP, it is always going to be "that draconian". But 80HP will not fall into a standard size, VFDs come as 75HP and then 100HP but the 75HP should do fine. Technically the ratio is 1.732 x the 3 phase motor current, in reality the VFD needs to be closer to 2x because you need extra capacitance to smooth out the extra ripple in the DC bus caused by the 1 phase input. So a typical 40HP 3 phase 230V motor will have an FLA of 104A. A typical 75HP 230V VFD will be rated for 210A, so really, no problem from the standpoint of suitability of the 75HP VFD.

But we come full circle back to the issue that boaterbill first brought up, your 200A service is too small for this motor.

As to the breaker to use, the NEC calls for the breaker to be max. 125% of the VFD INPUT current. That 210A VFD has an input current of 231A, so the breaker would be 250A.

 

[LionelHutz]

This is a 3-phase motor?

Are there any code rules (NEC, CEC or code where you are) that dictate the minimum size of the breaker (or fuses)? I wouldn't think any code would give a minimum breaker size but I could be wrong. Most codes dictate the minimum wire size and maximum breaker size for safety and protection purposes.

In theory, the Mirus 1Q3 filter should lower the distortion and also allow a 60hp VFD to be used instead of a 75hp. This will save cost on the VFD and lower the total current draw on the power system. Some type of harmonic filter will likely be a necessity to avoid causing voltage distortion on the power system. However, the 1Q3 filter itself is very expensive.

As others have pointed out, you will be running very close to 200A if the motor is running at full load and the service really is too small. But, if the motor is not at full load then it may be ok. The other alternative is to limit the max speed slightly. For example, drop the max VFD frequency from 60hz to 55hz. The current drawn from the line by the VFD is fairly linear to the hp drawn off the motor shaft. So, lower the hp by 10% and you lower the VFD current draw by about 10%.

 

[winterrules]

Thanks a lot for the help guys. Most of the info has been over my head so I forwarded this post on to our electrical guru so we'll see what he thinks. The problem is that the project is in the middle of nowhere (Adirondacks of NY) and the town went ahead on their own and just installed the 240V 200A service so we're kind of stuck with it. We might end up using a 30HP pump to get by with what electric we have and deal with the lower water flow rate.

I'm trying to learn as much as I can about electricity, but I seem to find things that are either elementary or way beyond my understanding...do you guys know of any good resources that I could check out to get a better handle on it?

Thanks a lot and more ideas are always welcome!

 

[jraef]

For those who were questioning whether or not it was a 3 phase motor, remember he said it ALREADY has a VFD, and there are no VFDs for 40HP 1 phase motors (that I know of), so we can deduce that it is a 3 phase motor.

So winterrules,
If you change to a 30hp pump you will still be able to use that existing VFD (assuming you have someone competent to re-program it) and utilize a smaller CB to feed it. Just make absolutely sure whoever reprograms it knows all of the limitations you have with your installation.