AC motor with capacitor:  barely any power - Page 1
Forum section: electronics / beginners

author: anvoice
author_rank: Frequent Contributor
timestamp: July 21, 2018, 09:59:42 pm
content: I have a 60rpm, 110V synchronous as motor with start capacitor (provided by motor seller so properly sized) that I've wired according to the instructions, but cannot get to spin with any appreciable force: I can easily stop it with a light touch. The motor is 6W, so it should be capable of more torque than what I'm observing.The motor has 4 wires coming out of it: one green, one red, and two yellow which I believe are the start winding wires. The instructions call to join the yellow wires together and attach to one of the legs of the capacitor, and to attach the red and green wires to opposite legs of the capacitor. My connection looks like this:red wirepower______ |______________| |green wire |cap|power______ |__________|___||yellow wiresCould this be a bad cap? If not, are there other reasons for the motor to be delivering sub par torque? Thanks in advance.

author: Andy Watson
author_rank: Super Contributor
timestamp: July 21, 2018, 10:58:43 pm
content: Could you draw a diagram, or even photograph what you have done? Your description suggests that you have connected both motor windings and the capacitor in parallel, and/or you have a strange capacitor with three legs - none of which sounds right!Do you have an ohm meter to confirm which of the motor wires are common to each other?Also, 6W ? Even if it's correctly wired it's barely enough to take the skin off a rice pudding.

author: anvoice
author_rank: Frequent Contributor
timestamp: July 21, 2018, 11:08:08 pm
content: Thanks for your reply! Sorry about that, I've attached what is hopefully a clearer diagram.6W is the largest power rating I could find with a can compatible with my current design. Also, I can attest that a 3W motor (albeit at 20 rpm) spun with enough force for my purposes (powering an orbital rotator for mixing chemicals): I couldn't stop it with my hand and it spun a loaded tray of chemicals easily enough.

author: anvoice
author_rank: Frequent Contributor
timestamp: July 21, 2018, 11:17:19 pm
content: Appreciate the input, but could you clarify what is incorrect? I'm asking in the beginner section because I'm, well, a beginner.

author: Andy Watson
author_rank: Super Contributor
timestamp: July 21, 2018, 11:27:31 pm
content: Ah, that concurs with my interpretation of your description, and, unfortunately, it's definitely wrong!Do you have any means of identifying which motor wire connects to which coil ? With such a small motor the capacitor will most likely go in series with one of the motor windings. It's likely to be permanently in-circuit - i.e. it is a run capacitor too.Does the motor have a type number or other means of identifying specific information ?

author: anvoice
author_rank: Frequent Contributor
timestamp: July 21, 2018, 11:35:34 pm
content: I used the instruction provided by the motor seller to wire this motor, which is attached below. It doesn't seem like the clearest thing in the world, but it's all I had to go on.Here's the motor information:synchronous motor50ktyz 110V AC 6W50/60r/min 50/60Hz0.56uF/630V Class EIP00 NO:1803018

author: Andy Watson
author_rank: Super Contributor
timestamp: July 21, 2018, 11:45:36 pm
content: Blueskull has it.This:Quote from: blueskull on July 21, 2018, 11:23:47 pmOk, just seen your latest post - with photo. Substitute black wires for yellow wires.Or, starting from the begining:Wire the capacitor between green and red wires.Join the two yellow wires together.Connect one power lead to the two yellow wires.Connect the other power lead to the green.If the motor turns the wrong way, swap the power lead from the green to the red connection.

author: anvoice
author_rank: Frequent Contributor
timestamp: July 21, 2018, 11:51:35 pm
content: Ok, I need to go read the theory behind how that's supposed to work. Thank you for your help, I'll report back as soon as I'm done desoldering the current setup.Reporting back: Everything works reasonably well now. Can still stop the motor but much harder now, so it'll hopefully serve its purpose. Thanks again for your help guys!

author: james_s
author_rank: Super Contributor
timestamp: July 22, 2018, 12:16:29 am
content: Your diagram and the photo provided do not match.The theory is pretty simple, the capacitor creates a phase shift, so depending on which winding is fed through the capacitor, the direction of rotation will change.

author: amyk
author_rank: Super Contributor
timestamp: July 22, 2018, 03:22:11 am
content: Permanent split capacitor motor. Study the diagrams.

author: anvoice
author_rank: Frequent Contributor
timestamp: July 22, 2018, 07:07:52 pm
content: Will do guys, I can see now I misread the connections photo.Always appreciate the help!

author: Jwillis
author_rank: Super Contributor
timestamp: July 23, 2018, 03:14:56 pm
content: Not sure if this is the same motor you have.But I'll take a shot in the dark.

author: anvoice
author_rank: Frequent Contributor
timestamp: July 25, 2018, 12:14:48 am
content: The motor is not the same but similar. This one looks like a higher power version with a different can design, but the connection in the photo is correct. I've since wired my motor in the same way and it's working without issue (other than being only 6W).