| Author | Message | ||
     Robert Noel Reddington Prolific User Username: bob_uk Post Number: 293 Registered: 5-2015 |
The early shadow had series field motors. Series field means that to reverse the motor either the armature polarity needs to be changed or the field polarity but not both. The early shadow changed the polarity of the field windings to reverse the motor. The later shadow used permanent magnets which cannot be reversed. So to reverse the polarity of the amature is changed. Why permanent magnet. About 1960 ish advances in permanent magnets made permanent magnet motors more powerful. This makes permanent magnet motors cheaper than series field wound. Before working on any electric motors its important to understand the difference. Wikipedia do an excellent write up on electric motors. Note some permanent magnet motors have magnets so powerful that taking them apart is dangerous to ones fingers. Fortunately the window lift motors aren't that powerful. | ||
| Martin Taylor Experienced User Username: martin_taylor Post Number: 11 Registered: 7-2013 |
With respect, a series field motor has the field in series with the armature or inter poles then armature, if the armature is stalled then current increases in the field and provides much more torque as armature current will decrease with speed. You are referring to an electrically excited field and a permanent magnet motor, the window motors are not series motors | ||
| Robert Noel Reddington Grand Master Username: bob_uk Post Number: 312 Registered: 5-2015 |
Martin you are absolutely correct the motor is not series wound but parallel. However the same applies about reversing the motor. In this case the field windings are reversed. |
