chemtech89 Posted September 19, 2013 Share Posted September 19, 2013 Hey guys I just finished my ball mill. It uses a PM DC 1 phase motor at 14v to achieve my targeted RPM. When the motor is spinning, it has plenty of strength to spin my 40 lb mill jar. However, it wont start on its own and I need to get the drive roller spinning first. All of this without the load from the jar. I'm having trouble finding the answer on google so I decided to ask you guys here. If I put a large capacitor parallel with the motor circuit will it give the motor extra strength to start? A little more about the symptoms... If the motor didn't move at all I would have doubts about the capacitor. However, the motor briefly jumps and spins the drive roller by a 1/4 (or maybe more) rotation then pauses, then jumps again over and over unit I use some force on the drive roller to get it moving. This "jumping" is associated with the "on" light to my power supply turning on and off. My assumption is the power supply doesn't have enough amperage to start the motor even though it has enough to keep it spinning. The power supply is 20A at 12v and my motor is 16.5A. Like I mention before, the voltage is at 14v which I adjusted to get my targeted RPM. When the power supply is at 12V, the motor will do the jumping thing its been doing but after 10 seconds as the jumping frequency increases it finally builds enough speed to get going. Do you think I just need a power supply with more amperage or do you think a capacitor will smooth out the gaps between the jumps enough to get it going? Any help is very much appreciated! Link to comment Share on other sites More sharing options...
a_bab Posted September 19, 2013 Share Posted September 19, 2013 It's your power supply for sure. Use a car battery intead of a cap. That would give you the initial "whomph" your motor needs. Also, your power supply is on the narrow side if used like this; it will eventually burn out, possibly causing you great pains in the arse. Link to comment Share on other sites More sharing options...
Arthur Posted September 19, 2013 Share Posted September 19, 2013 Too little power to start the drum turning. Try a car battery, a bigger PSU or try starting at 2v and turn it up to 14v over say 10 seconds. Without a bigger supply or less lead something is going to fail. You could reduce the rotating mass by using ceramic media. Makes it easier and quieter. Link to comment Share on other sites More sharing options...
Bobosan Posted September 19, 2013 Share Posted September 19, 2013 Agree with others as it sounds like the power supply. As mentioned, try the motor on a car battery. If it runs fine, you've narrowed the problem down. One other thought is that the PS may be a switcher rather than linear. Link to comment Share on other sites More sharing options...
chemtech89 Posted September 19, 2013 Author Share Posted September 19, 2013 What are your thoughts if I were to switch to a 30A power supply. I am deffenetly going to test with the car battery to narrow the problem down. I just don't want to have to add a car batt to my mill, trying to save weight where I can. Also, if a 3OA still doesn't have enough juice I could wire both the 20A and 30A in parrallel... I can't imagine 50A wouldn't be enough. These are all rough numbers. The supplys vary from 12-14v and are rated at the 12v so I'm obviously lower than the rated amperage being at 14v. I would check will the PS I already have but my multimeter doesn't measure amperage the high. Link to comment Share on other sites More sharing options...
Bobosan Posted September 19, 2013 Share Posted September 19, 2013 Use the car battery just for testing the motor as the battery should have enough amperage to start and run the motor. Carefully attach a pair of jumper cables instead of the power supply and load the mill up with jar and milling media to see if it will start and run without manually starting the rollers. Does the motor draw 16.5A just for starting or all the time it's running? Link to comment Share on other sites More sharing options...
Col Posted September 19, 2013 Share Posted September 19, 2013 (edited) I would say thats its running current, a 200w motor isnt all that powerful considering its turning a 40lb jar. I run slightly less weight on a 3/4hp (550w) ac motor. The inrush current of a dc motor is pretty high, so its possible the power supply`s current limiter is kicking in. Edited September 19, 2013 by Col Link to comment Share on other sites More sharing options...
chemtech89 Posted September 19, 2013 Author Share Posted September 19, 2013 Yes I understand the car batt is just for testing. 16.5A is the only rating on the motor so it must be running specs. As far as I know electric motor require more amerage when starting. I beleive that is whats happening Col, that the draw is too great for the power supply to keep pushing power so the limiter is kicking in. If only it was regulated and held at the 20A for a moment to get it spinning it would be fine but it cuts all power for about half a second. When the motor is on its own the power supply runs the motor perfectly. However, the belt, pullys, and drive roller create enough load which keeps the motor from starting correctly. So, its not alot of load but clearly enough to hit the limiter. Im going to purchase the larger power supply and see if I can use it on its own or I may need to put them both in parrellel. Link to comment Share on other sites More sharing options...
Bobosan Posted September 20, 2013 Share Posted September 20, 2013 Watch the amp ratings when running dual power supplies. Too large a difference between the two could also cause problems during motor start. What was the original use of this motor? Link to comment Share on other sites More sharing options...
chemtech89 Posted September 20, 2013 Author Share Posted September 20, 2013 (edited) I'm not sure what it was used for if anything specific. It a Dayton model: 4Z529. Can you explain a little bit further? A problem like burning out the motor or possibly the larger PS back feeding into the smaller one? If its the later, could I use diodes to prevent this? Edit: Earlier today I ordered a 30A PS. It looks to be a similar model as the first just stepped up. They're from ebay shipped from China. 110AC to DC 12v 30A. Edited September 20, 2013 by chemtech89 Link to comment Share on other sites More sharing options...
Bobosan Posted September 20, 2013 Share Posted September 20, 2013 That's a nice motor and your new 30A supply should be able to handle the current draw which is rated 16.2A @ full load. Link to comment Share on other sites More sharing options...
marks265 Posted September 20, 2013 Share Posted September 20, 2013 I've worked with motors like this in the past but never tried to connect them to full voltage. I was always accustomed to using a DC drive with motors like this. Using a drive will give you adjustments to the motor such as ramp up time and max current for examples. A typical application for a motor like this would be to run a small conveyor belt. The motor you have is rated at 1/6th HP, maybe the drive is needed to help with start up under load???? Also full load torque is rated at 6.38 inch pounds. That isn't a heck of a lot. With that said it still does surprise me that the motor is rated with a FLA of 16 amps. Link to comment Share on other sites More sharing options...
chemtech89 Posted October 31, 2013 Author Share Posted October 31, 2013 Update: I just installed the 30a 14v power supply to my ball mill and it starts up fully loaded no problem. Thanks for the help guys! Link to comment Share on other sites More sharing options...
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