Planer: Trips the Power Source Circuit Breaker

The armature is the power-producer of the motor and is the only moving part. The armature is surrounded by the field and is made up of wire winding's, which can fail for different reasons and cause the power source to trip. To examine the condition of the armature, and to perform tests on it, you will need to access and remove it from the planer. Start by removing the side covers and the gear box cover. Remove the retaining rings holding the sprockets and chain in place and then slide them off the shafts. Take off any spacers. Release the tension on the belt tensioner and remove the belt. Not all planers have a tensioner, so removing the belt can be tricky and require some patience. You may have to gently pry it off with a screwdriver as you walk it off the pulleys.
Remove the power cable hold-downs, followed by the bolts securing the motor housing to the planer. Lift up the motor and detach the ground wires under it. Place the motor on a bench and then remove the brush caps and brushes from the motor. Remove the switch from the switch housing and take a photo of the wire attachments before disconnecting them. Separate the switch housing from the motor housing, feeding the wires out with it. Remove the screws on the back cover of the motor and then the retaining ring behind the pulley, on the opposite end of the motor. Tap the pulley with a rubber mallet to free the armature from the motor housing and then remove the back cover from the armature and remove the spring washer off of the armature shaft. Clean the armature only with electrical contact cleaner and wipe dry. Examine the armature for melted windings and burn marks, which means a smoking armature.
Now, replace the armature. If you wish to check the condition of the armature, there are three tests you can perform. The first is a continuity test. With the armature removed from the unit, stand it up on a bench. Attach one end of the ohmmeter to the shaft, for ground, and the other to the bar on the commutator. Move the probe to each bar on the commutator, checking all of the bars. If the ohmmeter shows a reading on one of the bars, this will indicate a short and a bad armature.
The second test is a bar-to-bar test, to determine resistance. Attach one probe to a bar on the commutator and the other probe on the bar right beside it. There will be a specific reading for this, depending on the design of the armature. But, most importantly, is there is not a large fluctuation here between the values, which would indicate a fault. If there is an increase in resistance, this will indicate there is a broken, or burned out, wire in the coil. If the resistance drops, then there is a short. Move around the commutator, checking each bar.
The third test is the 180-degree test. Attach the two ends of the ohmmeter on the commutator bars, directly across from each other. There will be a specific set of readings for this, depending on the design of your unit. Again, what is most important is that there is not a large fluctuation in values, which would indicate a fault. If there is an increase in resistance, that would indicate a broken or burnt wire. If the resistance drops, that would mean there is a short. Continue this test on all the bars. If an armature fails any of these tests, it is recommended that you replace it.
Slide the armature into the motor housing, being careful not to damage the field as you do so. Then, install the retaining ring behind the pulley. Reinstall the spring washer and cover on the other side. Attach the switch housing to the motor housing and feed the wires back through it. Reconnect the wires to the switch by referring to your photo. Reattach the ground wires and motor and place/secure the motor housing assembly to the planer. Reattach the power cord clamps and install any spacers onto the feed rollers. Insert the sprockets inside the chain and position them onto the shafts, aligning the keyways one at a time. The hubs on the sprockets face the planer. Install the retaining rings to hold the sprockets in position and then reinstall the gear box cover. Reattach the belt onto the pulley, adjust the tension and tighten to hold in place. Belt installations on models without a tensioner will be tricky and require some patience. You may have to manoeuvre the belt through tight clearances to the pulleys. Feed the belt on the smaller pulley first, then the larger pulley for easier installation. Pry the belt over the larger pulley, with a screwdriver, to get it started. You can place the tip of the screwdriver on the pulleys nut for leverage only – do not damage any threads on the height adjusting rods. Once the belt is on, you can turn the pulleys by hand and walk it on the rest of the way. Reinstall the side panels.

A bearing is a device used to enable rotational, or linear, movement and reduces friction and handles stress. As time goes on, bearings will wear out and, if left unfixed, will overheat, seize up and cause a heavy strain on the motor. This is a result of the motor overloading and tripping the power source circuit breaker. A seized bearing can cause the motor to produce an abnormal sound as the motor struggles to operate. If it is bad enough, the motor will not spin.
To check the armature bearings, remove the side covers and then the gear box cover. Remove the retaining clips located on the feed roller shafts that holds the sprockets and chain on. Remove any spacers on the feed rollers and then the bolt on the belt tensioning bracket to release the tension. Now, take off the belt.
Not all planers have a belt tensioner for easy belt removal and installation, so removing the belt can be tricky on models without one. You may have to gently pry it off with a screwdriver as you walk it off the pulleys. Remove any cable hold-downs and then unscrew the support for the motor. Lift up the motor and detach any ground wires under it. Place the motor assembly on a bench and then remove the brush caps and pull out the brushes. Remove the switch from the switch housing and take a photo of the wire attachments – this is easier for reassemble.
Detach the wires from the switch and separate the switch housing from the motor housing, and then feed the wires out of it. Remove the screws securing the back cover of the motor, followed by the retaining ring behind the pulley. Tap on the pulley with a rubber mallet to separate the armature from the motor housing. Pull off the back cover from the armature with the spring washer.
Spin the bearings to determine which one is bad – they should spin freely, with no noise. A worn bearing will spin rough and make a noise. A seized bearing will not spin or is tight when spinning. Pulleys attach in a few different ways; examine yours for a set screw on the side that holds it in place, if there is no nut holding it on the front of the pulley. If your model has neither, then the pulley is pressed on and you will have to use a puller to remove it. You may need to heat up the pulley for easier removal, if it is pressed on. Use a bearing puller to remove the bearings. If clearances are tight, then use a separator to remove the bearing. Place the separator on a flat surface, such as an open bench vice that only catches the two sides of the separator. Then, tap on the shaft with only a mallet, or brass hammer, to release the bearing. Tapping on the armature shaft with a regular hammer will cause damage. Install new bearings onto the shaft, using a socket that only makes contact with the bearings inner race to avoid damage to the bearing. Tap on the socket with a hammer to seat the bearing in place and then reinstall the pulley. To make it easier for pressed on pulleys, heat the pulley up to expand it, then tap it in place on the shaft. Install the spring washer on the armature shaft, with the cover, and place the armature back into the motor housing. Tighten the cover down. Install the retaining ring back behind the pulley, on the opposite end of the motor. Feed the wires back into the switch housing and reattach the wires to the switch (refer to your photo).
Fasten the switch into the housing. Reattach the ground wires located underneath the motor and reinstall the motor back onto the planer. Reattach the cord hold-downs and then reinstall the spacers on the feed rollers. Position the sprockets inside the chain and reinstall the sprocket and chain assemblies onto the feed roller shafts, making sure to align the keyways. The hubs on the sprockets always face the planer. Reinstall the belt on the pulleys, adjust the tensioner and tighten to hold. On models without a belt tensioner, belt installation can be difficult and requires a lot of patience. Carefully manoeuvre the belt into position, through the clearances. It may be easier to push through using a screwdriver – but be careful not to damage any threads on the height adjustment rods. When the belt is in position, start feeding it onto the smaller pulley first, a little way only, and then place the end of the screwdriver on the larger pulley nut only – gently prying the belt along the larger pulley. Once it is on the pulleys a little way, hand-turn the pulley and at the same time, push on the belt to walk it onto the pulleys. Reinstall the gear box cover and side covers.

Carbon brushes wear out because they ride on a commutator, supplying electricity to the armature. If the carbon brushes suffer any damage, or become worn very badly, they can produce other symptoms and cause the power source to trip. To inspect the carbon brushes, remove the brush caps on either side of the motor and pull out the brushes. Examine for any signs of damage, such as cracks, chips, a broken brush, uneven wear or anything else that looks strange. Brushes measuring a 1/8 of an inch, or less, are worn out and require replacement immediately. Install new brushes into the housing and install the brush caps.

The field is an electromagnet used to generate a magnetic field in an electro-magnetic machine. The armature is surrounded by the field and the two make up the motor. The field can malfunction for a variety of reasons and could cause the circuit breaker to trip. To examine the field, remove the side covers and the gear box cover. Remove the retaining rings that supports the sprockets and chain on the feed roller shafts by sliding them off. Remove any spacers as well. Release the tension on the belt tensioner and pull off the belt.
For models without a belt tensioner, removing the belt can be a task and will require patience due to tight clearances. Pry the belt off with a screwdriver, a little way, then turn the pulley by hand and walk it off. Remove the bolts securing the motor housing to the planer, followed by the cable hold-downs. Lift the motor up and detach the ground wires under it. Place the motor on a bench for easier disassembly and then remove the brush caps and brushes.
Remove the switch from the housing. Before you disconnect the wire connections, take a photo of how they attach to reference later. Detach the switch housing from the motor housing and feed the wires out of the housing. Remove the screws from the rear cover of the motor and take out the retaining ring behind the pulley, on the opposite end of the motor. Tap the pulley with a rubber mallet to free the armature from the motor housing. Take off the back cover and spring washer from the armature shaft. Remove the screws securing the field in place and pull out the field. Clean the field only with electrical contact cleaner and wipe dry. Examine the field for burn marks and melted winding's, which indicates high heat within the motor, caused by sparks, overloading the motor or a shorting-out field. Also, check for any other visible signs of damage. Replace the field if you notice anything wrong with it.
You can check the condition of the field by performing a couple tests. Using a multimeter, you can check the field for continuity. Set the multimeter to the ohmmeters and place a lead on each end of the coil in the field. You will have to perform this test for each coil in the field. If the reading is infinity for one, or more, of the coils, then the field is bad and requires replacement. If there is a major variance between the coils then the field needs to be replaced. Install the field into the housing a secure it in place. Reinstall the armature back into the field, making sure the spring washer is on the shaft. Reassemble the rear cover onto the motor housing. Reinstall the retaining ring on the opposite end, behind the pulley. Reattach the switch housing to the motor housing. Feed the wires through the housing and reconnect the switch – refer to your photo for wire attachment.
After you have reconnected the ground screws underneath it, install the motor back on the planer. Reattach the power cable clamps and install any spacers onto the feed rollers, followed by the sprockets and chain assemblies, aligning the keyways. When installing, make sure the hubs on the sprockets face the planer. Reinstall the retaining rings and then the belt onto the pulley. Adjust the tension then tighten the tensioner to hold the belt’s tension. Belt installation on models without a tensioner can be quite tricky and require a lot of patience on some models. You may have to manoeuvre the belt through some tight clearances by twisting the belt and using a screwdriver to feed it through to the pulleys. Be very careful not to damage the belt or the height adjustment rods. Once the belt is in position, feed the belt on the smaller pulley first and then the larger one. This allows for easier belt installation. Pry the belt over the larger pulley, using a screwdriver to get it started. Place the tip of the screwdriver on the pulleys nut for leverage only, to avoid damage to any parts. Once the belt is on, you can turn the pulley by hand and walk it on the rest of the way. Reinstall the gear box cover and side panels.

A damaged power cord will definitely cause the power source circuit breaker to keep tripping and also poses as a safety/fire hazard. Examine you power cord for cuts, frays, burn marks, exposed wires and anything else in question. To install a new power cord, remove the side covers and the gear box cover. Remove the retaining rings in front of the chain sprockets then proceed to remove the chain and sprockets. Take out any spacers on the rollers and then remove the belt. If your model has a tensioner then release the tension and slide the belt off. If your model does not have a tensioner, then use a screwdriver to gently pry the belt off of the pulleys, a little at a time, as you turn the pulleys by hand to walk it off. This can be quite difficult due to clearance issues.
Remove the power cable hold-downs and then the motor/switch housing assembly from the planer. Detach the ground wires under the motor. Remove the switch from the housing and take a photo of the wires for reference when reassembling. Now, detach the wires. Separate the switch housing and motor housing from each other, feeding the wires through it.
Remove the power cable and install a new one, feeding it into the housing. If needed, cut ¼ of insulation from the wire ends and crimp on the appropriate new connectors necessary to connect the switch. Reassemble the motor housing to the switch housing and then reinstall the switch on the housing, once it is reconnected. Reconnect the ground wires under the motor before placing the motor back onto the planer. Tighten the motor in place and then reconnect the power cable hold-downs. Reinstall the belt and tighten the tension, holding it in place. For models without a tensioner, start the belt on the smaller pulley first, a little way around, and then use a screwdriver to pry it over the larger pulley all of the way around, a little way. Once the belt is on a bit, turn the pulleys by hand and walk it on the rest of the way. Install any spacers back on the feed rollers. Reassemble the sprockets inside the chain and position them one at a time onto the feed roller shafts, making sure they align the keyways. Once they are on the shafts, slide them all of the way back and reinstall the retaining rings. Install the gear box cover and side covers.

A malfunctioning switch can cause the planer to keep tripping the circuit breaker. To examine the switch, remove it from the switch housing. Examine the back for signs of melting, indicating that the switch is overheating. Check the switch to see if anything is broken, causing it to ground out and trip the circuit breaker. To replace the switch, transfer the wires from the old switch to the new switch. Do no mix up where they attach too. Once completed, install the switch into the housing. 

The circuit breaker protects the motor from becoming overloaded. A malfunctioning circuit breaker in the planer will cause the power source circuit breaker to trip. To access the circuit breaker, remove the switch from the front panel. Remove the nut securing the circuit breaker in place, on top of the housing, and then proceed to remove the circuit breaker through the switch opening. Take a photo for reference of how the wires are attached. Now, you can disconnect the wires. Examine the circuit breaker for signs of melting (due to an overheating breaker), breakage or anything else out of the ordinary that could be impacting the performance of the circuit breaker. You can test the circuit breaker using a multimeter set to an ohmmeter. Place a lead on each terminal on the circuit breaker. In the ON position (button in the down position), you should get a reading. In the OFF position (button is in the up position), there should be no reading. If you circuit breaker is not doing this, or doing anything different, replace it. Attach the wires to the new circuit breaker and reassemble the breaker back into the housing. Install the nut to secure the breaker in place. Reinstall the switch.