soft starter for 10HP single phase 240V pump

Status
Not open for further replies.
T

T.M.Haja Sahib

Guest
kwired said:
When you have only one 10 Hp motor on a 10kVA transformer you usually have horrible voltage drop problems unless the motor is the only load.
Click to expand...
The American Electrician Hand book states the kva of the transformer should equal the h.p of the motor it is powering to keep the voltage drop within acceptable limits.So if the capacity of transformer were 30kva instead of 25 kva for case below it would have lasted far longer than 4 years.

Rampage_Rick said:
I had an irrigation pumphouse with 3x 10HP running off a 200A single phase service. They replaced a single 10HP, but nobody at the time noticed the pole pig was only 10kVA. Didn't last long before it went boom... The utility was going to replace it with another 10kVA, but I begged for something bigger and got a 25 kVA. Not ideal but it's survived 4 years.
Click to expand...
 
Last edited:
kwired

kwired

Electron manager
Location
NE Nebraska
T.M.Haja Sahib said:
The American Electrician Hand book states the kva of the transformer should equal the h.p of the motor it is powering to keep the voltage drop within acceptable limits.So if the capacity of transformer were 30kva instead of 25 kva for case below it would have lasted far longer than 4 years.
Click to expand...

You needed the AEH to figure that one out?

This also gets into a related thread - POCO's do not always size their equipment as we would for similar equipment that is indoors, I will refer you back to that thread instead of making this one go in another direction.
 
mbeatty

mbeatty

Senior Member
Location
Illinois
friendlyfire said:
Hello,
I have confirmed that the customer does indeed have 10HP pumps. They are ITT Goulds G&L series. As one poster suggests, no one seems to make a starter appropriate for this size in single phase. I note the last poster presents a method for using a three phase starter but Jraef presented a convincing argument about why this would not be possible. I've asked the pump vendor to assist but the situation looks a bit grim.
Click to expand...

What I posted is done, a lot, and it works quite well. :)
 
kwired

kwired

Electron manager
Location
NE Nebraska
mbeatty said:
What I posted is done, a lot, and it works quite well. :)
Click to expand...
And is only necessary if the overload senses phase loss, otherwise just use two poles. You must also use large enough contactor for single phase current. 10 Hp 230 volt 3 phase will be less current than 10 Hp 230 single phase. You very possible looking at NEMA size 2 for three phase and NEMA size 3 for single phase.
 
ptonsparky

ptonsparky

Tom
Location
NE (9.06 miles @5.9 Degrees from Winged Horses)
Occupation
EC - retired
SQ D digest 173 (2003) lists a DPA122 definite purpose contactor @ 25HP 1PH 230V. LRA of 720A and FLA of 120.

Again not soft start, but good gosh golly either change the pumps to 3 phase and convert via a VFD so you get the start you want or get the POCO to supply you with enough power to start them across the line. Sure sounds simple from here. Good luck.
 
M

mike_kilroy

Senior Member
Location
United States
T.M.Haja Sahib said:
The American Electrician Hand book states the kva of the transformer should equal the h.p of the motor it is powering to keep the voltage drop within acceptable limits.
Click to expand...

I am not familiar with this handbook: can you give me a link to it or more info how to find it to look at the reference you mention please?

thank you.
 
T

T.M.Haja Sahib

Guest
mike_kilroy said:
I am not familiar with this handbook: can you give me a link to it or more info how to find it to look at the reference you mention please?

thank you.
Click to expand...
[h=1]American Electrician's Handbook
by Terrell Croft, Wilford Summers and Frederic P. Hartwell
[/h]There is chance the book is available in your local library.
 
kwired

kwired

Electron manager
Location
NE Nebraska
ptonsparky said:
SQ D digest 173 (2003) lists a DPA122 definite purpose contactor @ 25HP 1PH 230V. LRA of 720A and FLA of 120.

Again not soft start, but good gosh golly either change the pumps to 3 phase and convert via a VFD so you get the start you want or get the POCO to supply you with enough power to start them across the line. Sure sounds simple from here. Good luck.
Click to expand...

I think we must just be spoiled here in NE. To not be able to start a 10 hp motor across the line whether single or three phase would be seen as absurd. We are used to starting up to 100 hp across line all the time and occasionally even larger. Soft starting small loads is usually done for the wear and tear on equipment or for solving voltage drop problems within the facility and not to make POCO happy.
 
mbeatty

mbeatty

Senior Member
Location
Illinois
kwired said:
And is only necessary if the overload senses phase loss, otherwise just use two poles. You must also use large enough contactor for single phase current. 10 Hp 230 volt 3 phase will be less current than 10 Hp 230 single phase. You very possible looking at NEMA size 2 for three phase and NEMA size 3 for single phase.
Click to expand...

Absolutely.
 
B

BrianMuir

Member
Location
Comox BC
Hello All,
In the interest of closing the loop on my original post, I am pleased to report that I attended the commissioning of this system today. The 10HP pumps are started perfectly by the Siemens 3RW3045-1AA12. As best I can measure the inrush is below 100A and the pumps starts very smoothly and quickly settle down to the 30-35A range.

Had I become involved in the project from the start I would have steered the client towards smaller pumps, but it is a great relief to have salvaged the situation. I hope the owner takes my recommendation and stocks a spare starter, because those babies are basically out of production.

Thanks to everyone for the support on this one.
 
Status
Not open for further replies.
Top