perm filename NOTES.1[1,VDS]1 blob sn#096880
filedate 1974-04-11 generic text, type C, neo UTF8
COMMENT ⊗ VALID 00003 PAGES
C REC PAGE DESCRIPTION
C00002 00002 MOTORS
C00004 00003 ARM PROGRAMS
Globe motor details.
Typical demagnetization results
As delivered - back emf equals 9.2
Take out magnets and replace- back emf goes to 8.2
Take out magnets and press like poles together until they touch-
back emf drops to 6.2 or so.
So we see the potential torque loss due to dissassembly.
Careful disassembly gives only a 157 torque loss, but fooling
around results in up to 50% torque loss.
A good test for fully charged globe motor magnets is to see if it cogs. If it
does, then the magnets are at least 75% charged. If it doesnt, then you
have weak magnets.
Placing the poles of a globe motor between the poles of a large alnico magnet
seems to properly recharge the magnets. As an example- recharging the motor above
in this manner yeilded a back emf of 9.6. Higher than the original number- but no
doubt, when put to use, the magnets can be expected to discharge a bit in the
presence of demagentizing armature current induced fields.
As a furthur note- testing the motor with the large charging magnet between the
poles gives an emf of over 15.
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