Took motor apart so I could see switch an all real good and all looked good. Put motor back together and it started 1 time and next time wouldn't start. Took motor apart again and 1 spring in centrifugal came off. So I suppose that is bad, I'll get another. Someone mentioned a solid state one but they looked way to high. When I run the motor I didn't put the run cap. back and it run fine. I found a used one same volt but 25uF instead of 15, will that be ok? Since it will run without a run cap. how do I know if it becomes bad?
- Thread starter ldj
- Start date
guido
Well-known Member
Hello ldj,
Fix the starting circuit first. Probably is all is wrong with the motor. Put the capacitor in the circuit. It should charge up. Remove it from the circuit. Touch one terminal with a screwdriver, slide the screwdriver towards the other terminal. If it is good it will spark before you touch the other terminal. You can charge the cap with a patch cord. The starting cap can be tested the same way. If you're comfortable doing it also. test it the same way. The motor must be a capacitor run motor. Put one in, even if it is bigger in capacity.
Guido
Fix the starting circuit first. Probably is all is wrong with the motor. Put the capacitor in the circuit. It should charge up. Remove it from the circuit. Touch one terminal with a screwdriver, slide the screwdriver towards the other terminal. If it is good it will spark before you touch the other terminal. You can charge the cap with a patch cord. The starting cap can be tested the same way. If you're comfortable doing it also. test it the same way. The motor must be a capacitor run motor. Put one in, even if it is bigger in capacity.
Guido
You should use identical capacitors if
possible, and correct the issue with the
centrifugal start switch. Those are there for
a reason, and a significantly different size
capacitor will make a huge difference in not
only running torque of the motor, but amp draw
of the motor, and potentially lead to
overheating. Capacitors are difficult to test,
and simply charging up to see if it will spark
is not an accurate test, much like testing a
battery in that same method. Not just trying
to be a safety preacher, but I worked in
engineering for a large motor manufacturer for
many years mostly building and testing
prototypes.
possible, and correct the issue with the
centrifugal start switch. Those are there for
a reason, and a significantly different size
capacitor will make a huge difference in not
only running torque of the motor, but amp draw
of the motor, and potentially lead to
overheating. Capacitors are difficult to test,
and simply charging up to see if it will spark
is not an accurate test, much like testing a
battery in that same method. Not just trying
to be a safety preacher, but I worked in
engineering for a large motor manufacturer for
many years mostly building and testing
prototypes.
buickanddeere
Well-known Member
Do you know somebody that knows how to use an ohm meter. Randomly swapping parts and tinkering without really knowing that is going on is going to cost $$$, not have a working motor and may break something beyond repair.
The capacitors from the factory are minimum voltage and minimum uF for the application. Going higher voltage will make them less liable to fail due to voltage spikes. Higher uF on the run to a point, will reduce the reactive current demand from the power utility. Higher uF on the start capacitors will increase starting torque.
You need a capacitor tester or a VOM that has a uf setting to
test a capacitor. If a run capacitor goes bad the motor amps go
up and cause the motor to overheat. As for using a 25 in place
of a 15, no it has to be within 10%. Also when testing it should
be within10% if not replace it with same size.
test a capacitor. If a run capacitor goes bad the motor amps go
up and cause the motor to overheat. As for using a 25 in place
of a 15, no it has to be within 10%. Also when testing it should
be within10% if not replace it with same size.
buickanddeere
Well-known Member
The tin can run capacitor which is always energized can be up sized to double with no ill effects. In fact line losses will be reduced due to less reactive power being circulated from the utility. The motor's thermal overload would be down sized to match motor current that is closer to unity PF instead of being 0.8 to 0.9 .
The plastic and carboard start capacitors which are in series with the start windings and are only energized while the starter switch is closed . They can be doubled in sized as well. This will increase starting torque due to a greater leading phase shift between the start and run windings.
We ran labs on this at school and ran dyno tests to monitor the effects of capacitors.
The story that motor starters can not be up sized is an old wives tale. Where a cap can not be up sized is in some tuned RF circuits in radio receivers .
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