[RE-wrenches] Autotransformer for Single Phase Motor Headache

[Jay]

Hi Chris 

I googled and a new 3phase motor is about $1000 and the vfd is about $500 maybe. Say $3000 for the upgrade?

Seems like the easiest to do, easier on the existing inverters, it’s the least expensive long term option. 

I don’t know what the transformer would provide as a fix because the pump is already 240?  

I’m not even going to ask if he actually needs a 7.5hp motor. 

Jay


> On Jan 28, 2022, at 9:46 AM, Chris Sparadeo <sparadeo.chris at gmail.com> wrote:
> 
> 
> Hi all,
> 
> I currently have an off-grid client that has a 120/240VAC  7.5 HP -  40A FLC single phase pool pump. Locked rotor current is around 110 A. I had initially (and naively) thought that two Sol Ark 12k units would be able to handle this load. Due to the lack of a transformer, the unit's just can't output the required inductive startup inrush. Now getting clarification from Sol Ark that max inductive HP output is 2.5 HP per unit. We had installed an amply sized SR35 soft starter, with no avail. The 20 kW generator can start the motor, but it is noticeably shaken with the intense load drop. 
> 
> I am toying with the idea of installing a VFD and upgrading the pool pump to a three phase motor. Would make for a much smoother ramp and self start. The client is a bit hesitant to upgrade and would like to continue using their clunky, non-self starting single phase motor.  
> 
> My other thought was to implement an autotransformer to add some copper to the equation and help the Sol Ark's get the job done. Has anyone had any experience with the Victron 100A autotransformer for both 120/240 input and output? 
> 
> Any suggestions or relative experience would be greatly appreciated!
> 
> -Kindly,
> 
> -Chris
> 
> --
> Chris Sparadeo 
> NABCEP Certified PV Installation Professional ® # 042919-015652
> NABCEP Certified PV System Inspector ® # 052920-015652 
> State of Vermont Journeyman Electrician # EJ-07619
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