Does Open Delta Service shorten three phase motor life 6

[HVmazz]

I have a proposal to install a replacement (~pump cost = $4,000) 10 Hp water pumping system which is serviced with an Open Delta three phase 240 volt 50 KW utility supply. The old system has experienced three motor burn-outs in the last 4 years. The new motor is rated at 10 Hp, 230 volt, three phase, 28 F.L.A.and has a manufacturers 5 year/10,000 Hr. warranty. I will be adding phase loss/reversal, over, under & unbalanced voltage & short cycling monitoring to the control panel. The manufacturer will honor the full warranty ONLY if "...the 230 volt/3 phase 60 Hz power source is a good dependable supply and NOT originating from an Open Delta power circuit". The utility company engineering department claims this type of service is normal and wants $5,000 to add the third transformer to the service to yield 208/120 three phase which would also require a new motor selection. We also have a small single phase lighting load. The pump manufacturer will make changes to the motor windings to accomodate the 240 Volt Open Delta supply. How much will the pump life be shortened running on an Open Delta source? Should we add our own transformer on the secondary side?

 

[itsmoked]

I'm hoping jraef or someone else will answer your last question too.

I have many times used VFDs on single phase but would like to hear from a VFD wizard if there are any hitches with hooking a typical VFD to open delta?

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[itsmoked]

HVmazz;
Your original open delta question has been answered. Now VFD savvy members are likely passing over this original thread not realizing there are VFD follow-ons.

I suggest you start another thread asking specifically;

Title: Powering a VFD with Open Delta

"Should I run a 10hp VFD on Open Delta 3 phase or use a higher power rated VFD and feed it single phase 240V?

What are the potential problems?"

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[jraef]

Some VFDs cannot tolerate having any kind of grounded delta system feeding them, others couldn't care less. It depends on the design. Most of the majors have an option of removing a grounding jumper to accommodate a grounded delta. Other than that, no issue. If you can tolerate the additional cost however, oversizing a drive is never a bad thing, it allows for a wider variance in input power conditions. Given that your pump is likely a centrifugal, simply buying a 15HP Constant Torque rated drive will make it effectively double the necessary size for your 10HP pump (because you could have probably gotten away with using a 7-1/2HP CT rated drive on a 10HP VT pump).

Not meaning to espouse any one brand over another, but the Teco FM100 drive has a cool built-in timer feature with which you can directly implement the variable flow rate pattern itsmoked mentioned. I have done dozens of fountain pumps with them. You can set up 7 speeds and times, each with their own ramp up and down times of up to 60 minutes each, so by the time you run through an entire 7 cycle program, the average viewer has moved on, thinking it was entirely random.

JRaef.com
"Engineers like to solve problems. If there are no problems handily available, they will create their own problems." Scott Adams
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[HVmazz]

Thaks for sharing you experience and expertise.... itsmoked has suggested starting a new thread specifically addressing the VFD options...
Thanks again... All of the responses have helped expand the range of options ...

 

[HVmazz]

jraef ... Thanks for the tip I am looking at using a larger drive as you suggest... The time/speed programming would be a real attraction... Thanks again.

 

[EdDanzer]

You may want to consider running a three phase motor idle in parallel. This is used in phase converters with good success.