How to Check Rotor Angle Grinder with a Multimeter

To check the stator and rotor for an interturn circuit with a multimeter, it does not take much time. It will take longer to disassemble the engine. Angle grinder, drill, puncher. Each tool can be repaired by determining a malfunction. It is better to break the check into several main stages, and sequentially take steps slowly.

Dismantling angle grinder

To check the short circuit on the stator and rotor, you need to disassemble the engine of a household tool. Consider performing this operation to troubleshoot an angle grinder.

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  Remove the protective cover by unscrewing one screw on the clamp;

• Unscrew the 4 screws and disconnect the gear with the engine from the handle of the angle grinder;
• Then on the gearbox side, unscrew 4 bolts and disconnect the gearbox, together with the motor rotor;
• The stator in our case remained connected to the power and power button.

Having disassembled and disconnected the parts necessary for verification, we proceed to their external inspection by checking for inter-turn closure.

Visual inspection

A malfunction can be detected by uneven heating of the tool body. Touching your hand, you feel the temperature difference in different places of the case. In this case, the tool must be disassembled and tested with a tester and other methods.

In the event of a short circuit of the stator turns and troubleshooting, first of all, we conduct an inspection of the turns and conclusions. As a rule, when closing, the current flowing through the windings increases, and their overheating occurs.

There is a greater closure of the turns in the stator windings and the insulation layer is damaged. Therefore, we begin the determination of malfunctions by conducting a visual inspection. If burn-through and damaged insulation are not found, then proceed to the next step.

Perhaps the cause of the breakdown is a malfunction of the voltage regulator that occurs when the excitation currents increase. To detect a problem, the brushes are checked, they must be sharpened evenly and not have chips and damage. Then check with a light bulb and 2 batteries.

Multimeter application

Now we need to check the possibility of breaking the stator windings. On the multimeter scale, set the switch to the resistance measurement sector. Not knowing the measurement value, set the maximum value for your device. We check the performance of the tester.

Touch probes of each other. The arrow of the device should show 0. We carry out the work, touching the conclusions of the windings. When an infinite value is shown on the multimeter scale, the winding is faulty and the stator should be rewound.

We check the possibility of a short circuit to the case. Such a malfunction will cause a decrease in power of the angle grinder, the possibility of electric shock and an increase in temperature during operation. The work is carried out according to the same scheme. We include resistance measurement on the scale.

We place the red probe on the output of the winding, and attach the black probe to the stator housing. If the winding is shorted to the housing on the tester scale, the resistance value will be less than on a healthy one. This malfunction requires rewinding of the stator windings.

It is time to take measurements and check if there is an interturn circuit of the stator winding. For this, the resistance value on each winding is measured.

We determine the zero point of the windings by measuring the resistance for each of them. If the device shows the least resistance of the winding, it should be changed.

Custom check

The most accurate way is to check the stator using a metal ball and a step-down current transformer. The stator is connected to the terminals of the three phases from the transformer. After checking the correct connection, we turn on our low-voltage circuit in the network.

We throw a ball inside the stator and observe its behavior. If it “stuck” to one of the windings. This means that an interturn circuit occurred on it. The ball spins in a circle. The stator is working. A rather unscientific, but effective method for detecting interturn circuit on a stator.

Rotor malfunctions

In the case of optimal use, the rotor does not wear out. Routine maintenance is carried out with the replacement of the brushes when they are worn. But over time, under heavy loads, the stator heats up and carbon deposits form. The most common mechanical failure is wear or misalignment of the bearings.

The angle grinder will work, but at the same time, the plates quickly wear out, and over time the engine breaks. To avoid damage, it is necessary to check the tool and maintain normal conditions of service.

Moisture in contact with metal causes the formation of rust. The frictional force increases, the current strength is required more to work. Significant heating of contact groups occurs, solder, a strong spark appears.

Checking motor windings

The electronic rotor tester is a standard digital multimeter. Before proceeding to test the circuit, you should check the multimeter and its readiness for work. The switch is set to measure the resistance and touch the probes with each other. The device should show zeros. Set the maximum value of the measurement and check:

• First check the rotor for an open circuit. Touching the black probe to the slip ring, the windings should ring red. The arrow of the device is off scale, which means that the winding has an open circuit of turns. The rotor should be rewound;
• Measure the resistance to determine the possibility of a short circuit to the housing. We fix the black probe on the contact ring, the red rotor should ring to close the rotor case. In the case of a low reading of the resistance value and the sound signal, such an anchor must be given for repair;
• Conducting ringing on the inter-turn circuit of the turns of the rotor. We reinforce the probes on the contact rings of the anchor. With a value on the scale of the device, from 1.5 Ohms to 6 Ohms, we tested a working device. All other values ​​on the scale indicate a malfunction of the multimeter.

This completes the verification of the rotor. Once again, the main steps in determining the malfunction should be recalled. Before checking, the angle grinder or any other device should be de-energized.

Before taking measurements, you should visually inspect the housing, insulation and lack of deposits on the stator and rotor.

It is necessary to clean the contact surfaces from blockages with dust and dirt. Pollution leads to an increase in current during loss of motor power.

When disassembling the tool for the first time, record all your steps. This will allow you to have a hint the next time, to avoid the appearance of unnecessary parts during assembly. When the brush leaves the edge of the brush holder less than 5 mm, such brushes should be replaced.

You can check the inter-turn circuit with an electronic tester, that is, a multimeter.