Hello and welcome to Grizzly's motor
troubleshooting and repair video. My name is Kent and this is one in a series of how-to videos
we're producing making it easier for our customers to upgrade and maintain their Grizzly equipment.
This is Shawn, an engineer here at Grizzly, and together we're going to show you step by step
how to easily check some common motor components and how to adjust or replace them if needed.
We recommend you watch this entire video and contact our technical support at 570-546-6966 if
you have any questions or need further assistance. Start capacitors are connected to the start
windings in single phase induction motors and provide an artificial second electrical phase
to allow starting.
They do this by storing and releasing an electric charge that is out of phase
with the main or run windings, which creates a rotating magnetic field that starts the motor
turning. This is the centrifugal switch. After the motor starts and reaches operating speed, the
centrifugal switch disengages and the capacitor is no longer connected to the circuit, because it is
only needed for starting. When a capacitor fails, or the centrifugal switch shifts out of
adjustment, the motor may hum without starting, start sluggishly, or trip a circuit breaker.
The following steps will take you through troubleshooting these components.
Capacitor
inspection and testing. Disconnect the machine from the power supply. Use caution when working
with capacitors. They can store a significant electrical charge even after the machine has
been turned off. To avoid getting shocked let the machine sit for at least five to ten minutes
to allow the capacitor to naturally discharge before performing any work. Motor capacitors
are typically located outside the motor housing, underneath a half-round cover. To access,
simply remove the two screws that hold the cover on and lift the cover off. As an extra
precaution against being shocked, short the leads on the capacitor with an insulated or wood
handle driver. Before touching any bare wires, the screwdriver must contact both leads at the
same time. Be careful as there is a small chance for an arc or spark when this is done.
Make sure
there are no flammable materials nearby and that you're in a safe environment where a spark would
not cause a fire or an explosion. Now inspect the capacitor closely for signs of damage, such as
bulging, bursting, or leaking oil. If you see any of these signs, the capacitor must be replaced.
If there are no visible signs of damage, test the capacitor with an analog or a digital multimeter.
The meter should be set to the ohm setting. Place the tester leads on the capacitor terminals.
The multimeter scale should start at zero and then rise to infinity. Here is how it looks on an
analogue type meter. Here is what you should see on a digital type meter. If there is no reading,
or the reading fluctuates up and down, then the capacitor is dead or it has an internal short
and must be replaced. The replacement capacitor must have the same microfarad value and a voltage
rating equal to or higher than the original. Next we are going to look at centrifugal switch and
contact plate inspection and adjustment. Over time the centrifugal switch may shift out of
adjustment, which can cause the start capacitor to fail.
To check the centrifugal switch, first
disconnect the machine from the power supply. Remove the fan cover from the end of the motor
then loosen the retaining screw and remove the fan from the motor shaft. Remove the dust cover,
if there is one, loosen the retaining screw on the centrifugal switch and slide the switch off the
end of the shaft. Locate the points on the contact plate and make sure they are in the open position.
If they are closed, bend the circular spring flat so the points no longer contact one another.
If the points are welded shut, then the contact plate must be replaced. Over time, the points on
the contact plate can develop a blackish carbon buildup due to the capacitor discharge during the
startup phase. This is normal and will not affect startup.
Look closely at the surface of the points
for signs of pitting. Light pitting can be gently sanded with some 400 grit sandpaper. But larger
deformities on the surface of the points will cause an unusable condition and potential arcing.
If excessive pitting is detected, the contact plate should be replaced. Now that the quality
of the contact points has been verified, you can reinstall the contact plate. Place the centrifugal
switch back on to the motor shaft. Make sure the orientation of the switch is correct so the collar
and retaining screw face towards the fan end of the motor. Slide the body of the centrifugal
switch further onto the shaft until you see the contact points barely touch each other.
Temporarily secure the collar with the retaining screw and mark the motor shaft with a felt-tip
pen just above the collar. Now loosen the screw on the collar and adjust the centrifugal switch
further onto the shaft until it is 1/16 of an inch below the mark on the shaft.
Then tighten the
retaining screw on the collar. If the switch is adjusted too far past the mark on the motor shaft,
the contact points may not open after the motor starts. This leads to capacitor failure, and the
next time the start switch is turned on, the motor will not start. Please use care when making this
adjustment to avoid damaging the capacitor. Once you are done, replace the remaining components in
the opposite order they were removed. Test run. Once assembly is complete and adjustments made to
your satisfaction, you are ready to test run the machine. Make sure the power switch is off then
plug the power cord in. When you turn the power switch on, make sure your finger is poised over
the off button just in case there's a problem. The motor should start and run smoothly. Well that's
it for this video. Hope we were able to help you..
