Small motor on UPS

[Npstewart]

I am looking for a UPS system to backup a very small motor, approximately less than a 1/4HP. The motor would almost NEVER be used on UPS power and would only be used in increments of about 30 seconds. Any ideas for manufacturers? The only thing I can find is a UPS for computers. Preferably I would like something that the motor could be wired into, most of the UPS systems have outlets in the back.

Thanks!

 

[gadfly56]

I am looking for a UPS system to backup a very small motor, approximately less than a 1/4HP. The motor would almost NEVER be used on UPS power and would only be used in increments of about 30 seconds. Any ideas for manufacturers? The only thing I can find is a UPS for computers. Preferably I would like something that the motor could be wired into, most of the UPS systems have outlets in the back.

Thanks!

You probably can't get anything from APC, where they usually top out at 1,000VA, but there are other folks out there making conversion kits for 2,000VA and up UPS's to hard wire them. Do a search for "UPS" threads, I know I supplied a link in one of them.

The critical thing of course is the inrush current at motor startup. If it's too high, you'll draw down the voltage to the point where the UPS will likely cut out.


Ha! found it: http://forums.mikeholt.com/showthread.php?t=140813&highlight=UPS,+emergency+light

 

[mike_kilroy]

So you want a .25hp*746w/hp=<200watt ups? Yes for inrush pick one larger - if motor is not already running when it might switch to ups power. But why NOT pick the really really low cost computer UPS you get at Walmart? The replacement 12v 7ah battery in 3 years will probably cost more than a brand new UPS then.....

 

[broadgage]

UPS units are not optimised for motor starting and in my experience need to be very much oversized in order to reliably start even small motors.

For refrigeration motors I have found that a UPS of TEN times the motor rating is required.
For example for a fridge with a nameplate of 160 watts, minimum 1,600 VA UPS.

My 2,400 VA UPS works a small freezer just fine, but wont start even a small air conditioner with a nameplate of 600 watts.

 

[gadfly56]

So you want a .25hp*746w/hp=<200watt ups? Yes for inrush pick one larger - if motor is not already running when it might switch to ups power. But why NOT pick the really really low cost computer UPS you get at Walmart? The replacement 12v 7ah battery in 3 years will probably cost more than a brand new UPS then.....

You forgot the part about hard wiring to the motor. That ain't happening witha 200VA UPS from APC. And inrush can be 8x run current, easy.

 

[pfalcon]

UPS units are not optimised for motor starting and in my experience need to be very much oversized in order to reliably start even small motors.

For refrigeration motors I have found that a UPS of TEN times the motor rating is required.
For example for a fridge with a nameplate of 160 watts, minimum 1,600 VA UPS.

My 2,400 VA UPS works a small freezer just fine, but wont start even a small air conditioner with a nameplate of 600 watts.

Would a soft start reduce the size requirement?

 

[gadfly56]

Would a soft start reduce the size requirement?

You can get a 1/4 HP soft starter from Newark Electric for about $160, and Grainger has 1/4 HP motors from $90 to $210 depending on features. I can't find out how much the soft starter limits inrush, however. On the whole, starting to get more complicated than you want for a 1/4 HP motor, IMO, but hey, whatever floats your boat.

 

[mike_kilroy]

You forgot the part about hard wiring to the motor. That ain't happening witha 200VA UPS from APC. And inrush can be 8x run current, easy.

Thanks clarify my answer. I DID say 200va is ok size in no start required (Yes for inrush pick one larger - if motor is not already running when it might switch to ups power) but it was indeed confusing how I said it. Thanks. Also made me re-read OP and instead of 'it can run 30 sec max' as I read it, it says it will run in 30 sec increments - meaning probably starting involved. So my reply, although technically accurate, is wrong. Thanks for catching that.

As for AC plugs, OP word of preferred does mean he is willing it listen to alternatives if good reason given to do so. Price of $ 39 vs $ 200 is valid alternative to consider in my book.

Thanks again for clarifying my post.

 

[stevephillips]

APC makes units well into the 10's on kVA. For what you are doing, a 3kVA unit should be able to start the motor just fine without a soft starter. I would suggest installing a PFC cap so the motor draw nearly unity though this is not absolutely necessary.

What does the motor power? Is this a cap start cap run or a cap start induction run?

 

[lixinglong]

You probably can't get anything from APC, where they usually top out at 1,000VA, but there are other folks out there making conversion kits for 2,000VA and up UPS's to hard wire them. Do a search for "UPS" threads, I know I supplied a link in one of them.

The critical thing of course is the inrush current at motor startup. If it's too high, you'll draw down the voltage to the point where the UPS will likely cut out.


Ha! found it: http://forums.mikeholt.com/showthread.php?t=140813&highlight=UPS,+emergency+light

You are right. We should think about inrush current. Generally speaking ,the capacity would be 5-10 times of rated capacity. Let's calculate it: 0.25x0.746Wx10=1860W, So 2000VA UPS is okay.
You can consult suppliers such as APC, Emerson, Santak etc, they all have this product.

 

[kingpb]

http://www.solidstatecontrolsinc.com/

They will build you whatever you need. :thumbsup:

 

[Npstewart]

Have you worked with these people KingPb?

 

[kingpb]

Have you worked with these people KingPb?

Many times over the years. Just recently finished detailed design on two projects were their equipment was used as replacement for existing equipment.

They can customize to your needs and can even work with you on dimensions of cabinets if it's a retrofit project and physical space is a constraint.