Eliminate starting torque of PMAC motor

Thread Starter

rrenk3000

Joined Jan 3, 2016
7
  • I'm trying to come up with a solution to eliminate the starting torque (twist) of a small 120vac 0.3amp PMAC motor. Similar, in effect, to how a start capacitor slowly starts an induction motor. Motor has a 4" fan blade attached and I want to suspend it from a flexible cord, but eliminate the twisting motion when started. Label on motor doesn't have it listed, but is approx 18watts. Alternate (compact design) ideas also appreciated.
 

MaxHeadRoom

Joined Jul 18, 2013
20,866
  • I'm trying to come up with a solution to eliminate the starting torque (twist) of a small 120vac 0.3amp PMAC motor. Similar, in effect, to how a start capacitor slowly starts an induction motor. Motor has a 4" fan blade attached and I want to suspend it from a flexible cord, but eliminate the twisting motion when started. Label on motor doesn't have it listed, but is approx 18watts. Alternate (compact design) ideas also appreciated.
More details on the motor is needed, if applying full 120v then there is no wonder it exhibits high starting torque, I assume there must be a controller of some kind, if PM motor?
The start capacitor in an induction motor is not for slow start, on the contrary, the faster it starts the better, the cap just provides a phase shift to the winding.
Max.
 

Thread Starter

rrenk3000

Joined Jan 3, 2016
7
More details on the motor is needed, if applying full 120v then there is no wonder it exhibits high starting torque, I assume there must be a controller of some kind, if PM motor?
The start capacitor in an induction motor is not for slow start, on the contrary, the faster it starts the better, the cap just provides a phase shift to the winding.
Max.
Max, the motor is currently switched on/off, full 120v. I am trying to create a pendant style fan (industrial look, see picture) that hangs from an overhead track with a flexible cord, and eliminate the twisting effect when it is switched on. I understand the concept of how a start capacitor actually works, but wanted to describe the effect of the slow motor start due to others wanting to "fix" my slow starting motor rather than see that is the desired effect. I have some room in the top of the housing to work with. Thanks...
 

Thread Starter

rrenk3000

Joined Jan 3, 2016
7
Cogging is the correct term for the twist motion from what I'm reading. The available literature seems to be associated with bigger motors.
 

Alec_t

Joined Sep 17, 2013
11,388
If you are hanging the motor from a cord there will be a continuing torque (not just a starting torque) while the motor is running, trying to twist the cord. Will the cord withstand that?
 

Alec_t

Joined Sep 17, 2013
11,388
Smaller maybe, but not nil according to Newton's Third Law. Think helicopter, need for tail rotor or other counter-torque device.
 
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