Will this power supply power this motor (needing verification) - Page 1
Forum section: electronics / beginners

author: jayfehr
author_rank: Contributor
timestamp: July 13, 2015, 04:53:58 pm
content: My plan is to build this bandsaw:http://woodgears.ca/bandsaw/homemade.htmlUsing this old treadmill motor:however they guy that saved the motor for me didn't pull the motor driver out. So I need a power supply/driver to power it. I found the one linked below on ebay, but I'm not sure if it'll work. In fact the low price kind of scares me. But from what I can tell it handles the proper voltages (90v) and since the motor pulls 8A the driver needs at least 720W and the supply is rated for 800W. To me it seems safe, but a second opinion, or some additional advice would be nice to have.http://www.ebay.ca/itm/DC-9-90V-10A-800W-Rectangle-PWM-Motor-Speed-Controller-w-B10K-Potentiometer-/310987278653?pt=LH_DefaultDomain_0&hash=item486849493d

author: leblanc
author_rank: Regular Contributor
timestamp: July 13, 2015, 05:05:06 pm
content: Remember that the torque is roughly proportional to the current (and the speed is roughly proportional to the voltage).The PWM will control the average voltage and therefore speed.The amount of torque you put on the motor will determine how much current is drawn. I have not seen numbers on torque for bandsaws, but I would imagine it is quite a bit smaller than a treadmill, depending on gear ratio. You'll probably only be drawing a fraction of that 8A rating. I would recommend putting a ~5A fuse to protect the motor, in case there is a large torque applied.Don't forget that there will temporarily higher torque when accelerating.You could also take a look at power ratings on off-the-shelf bandsaws if you want a ballpark figure.

author: PSR B1257
author_rank: Frequent Contributor
timestamp: July 13, 2015, 05:23:04 pm
content: You know, that you need a suited power supply first of, don't you?QuoteMe too. I wouldn't trust this thing any further I can throw itA simple way to drive the motor would be a variac and a diode bridge (the motor doesn't need any filter caps)

author: jayfehr
author_rank: Contributor
timestamp: July 13, 2015, 05:28:06 pm
content: I forgot to include the power supply I'm looking at. It's this one here:http://www.ebay.ca/itm/CNC-Switching-Power-Supply-800W-Ajustable-70-90V-11-4A-with-Cooling-Fan-/181251671363?pt=LH_DefaultDomain_0&hash=item2a33710543Outside of the 24V range I'm a little nervous about homebrewed solutions. My confidence just isn't there yet, and I do really like living.

author: PSR B1257
author_rank: Frequent Contributor
timestamp: July 13, 2015, 06:11:03 pm
content: QuoteAlways a good idea to be precautious at higher voltages.For reasonable money you can get a variac with enclosure.http://www.ebay.ca/itm/POWERSTAT-116CU-10A-0-140V-OUTPUT-VARIABLE-1-4KVA-120V-AUTOTRANSFORMER-B224696-/301584871818?pt=LH_DefaultDomain_0&hash=item4637dbf18aThere is also room for a diode bridge.Just saying...Hang on, what do you think ofhttp://www.ebay.ca/itm/Dart-Controls-510-100C-36M-DC-Drive-for-90VDC-Motors-120VAC-Input-/331450078184?pt=LH_DefaultDomain_0&hash=item4d2bf6d3e8Hmm... can't see a power rating...but I guess it's worth asking the seller.

author: Deathwish
author_rank: Unknown
timestamp: July 13, 2015, 06:37:04 pm
content: another good place to ask is in herehttp://www.ukworkshop.co.uk/forums/

author: Zero999
author_rank: Super Contributor
timestamp: July 14, 2015, 10:20:14 am
content: Quote from: PSR B1257 on July 13, 2015, 06:11:03 pmA decent quality, properly built 90VDC switched mode power supply should be safer than a Variac. It will be isolated from the mains and will output smooth DC, rather than 90VAC which has a peak voltage of 127V and can more easily disrupt the heart's rhythm than steady 90VDC.Voltages under 120VDC are still considered to be SELV, although above 60VDC there's a considerable shock risk so basic insulation from the user is mandatory.The motor may not be designed for direct connection to the mains so whilst a Variac will properly work, it's not a good idea.

author: flynwill
author_rank: Regular Contributor
timestamp: July 14, 2015, 02:19:56 pm
content: I would recommend a bit more research. There are supplies out there designed as speed controllers for DC motors. They sense the motor speed from brush switching and adjust the motor current for constant speed. Sherline uses such a controller on their lathes (but that controller doesn't have enough oomph for your motor).

author: flynwill
author_rank: Regular Contributor
timestamp: July 14, 2015, 03:07:20 pm
content: This looks like it might do what you want:http://www.kbelectronics.com/data_sheets/kbic.pdfAvailable from Amazon.

author: PSR B1257
author_rank: Frequent Contributor
timestamp: July 14, 2015, 03:28:37 pm
content: QuoteYes, but ausualAC-motor isn't isolated from mains either, if memory serves me correctly

author: Zero999
author_rank: Super Contributor
timestamp: July 14, 2015, 05:09:08 pm
content: Quote from: PSR B1257 on July 14, 2015, 03:28:37 pmThe difference is an AC motor will be designed for direct connection to the mains.