P
P E Schoen
- Jan 1, 1970
- 0
My friend had a problem with a 120 VAC heavy duty relay he connected to a
sump pump motor. It would turn on OK, but it would not release. If he tapped
the armature, it would open, and he suspected welded contacts, but they were
fine. It was the armature itself that was latching. So he put a piece of
paper over the armature, and it made a loud buzz, but it seemed to work
better. Then, when he removed the paper, it worked normally, with a solid
click on operate and release (where previously it would take a half-second
to open).
He had gotten this relay as surplus from an electronics company where we
both worked 30 years ago, and they used the same style relay with 24 VDC
coils. I think perhaps they had ordered these incorrectly and used them on
24 VDC, which may have drawn much higher current than usual and magnetized
the iron of the coil. When he added the paper, it created a gap and lower
inductance so the AC current was higher, and enough to demagnetize it.
Paul
sump pump motor. It would turn on OK, but it would not release. If he tapped
the armature, it would open, and he suspected welded contacts, but they were
fine. It was the armature itself that was latching. So he put a piece of
paper over the armature, and it made a loud buzz, but it seemed to work
better. Then, when he removed the paper, it worked normally, with a solid
click on operate and release (where previously it would take a half-second
to open).
He had gotten this relay as surplus from an electronics company where we
both worked 30 years ago, and they used the same style relay with 24 VDC
coils. I think perhaps they had ordered these incorrectly and used them on
24 VDC, which may have drawn much higher current than usual and magnetized
the iron of the coil. When he added the paper, it created a gap and lower
inductance so the AC current was higher, and enough to demagnetize it.
Paul