First, let's discuss common faults and their troubleshooting for single-phase motors.
1. The power supply voltage is normal, but the motor does not start after being turned on.
1) The power wiring may be open, resulting in no voltage across the terminals. This can be checked using a multimeter to confirm the absence of voltage.
2) Either the main winding or the auxiliary winding might be open. A DC resistance test can help identify an open circuit in the windings.
3) The centrifugal switch contact may not close, preventing the auxiliary winding from receiving power. This can be tested by measuring the DC resistance between the main and auxiliary windings.
4) The start capacitor could be open or internally damaged. A similar method to item 3 can be used to check this.
5) In shaded pole motors, the short-circuit ring may be broken. If it’s externally visible, you can spot it visually; otherwise, further testing is needed.
6) For series-wound motors, the brushes may not make proper contact with the commutator due to wear, jamming, or broken brush leads. Internal issues like open armature or field windings can also cause this.
2. The motor starts but runs at low speed, with a humming sound and vibration, and the current doesn’t drop.
1) The load may be too heavy, causing the motor to run slowly.
2) Mechanical friction between the stator and rotor may occur, leading to unusual noises.
3) Bearings may be damaged or improperly lubricated, causing the motor to vibrate and run inefficiently.
4) In series-wound motors, internal short circuits or misaligned brushes can cause abnormal operation.
3. The fuse blows immediately when the motor is powered on.
1) A severe short circuit in the windings or to ground can cause this. Measuring the DC resistance will show a much lower value than normal.
2) The motor leads may have a ground fault, which can be tested similarly to the first point.
3) A faulty capacitor may be shorted, which can be checked by measuring the resistance of the start winding circuit.
4) The centrifugal switch may be grounded, which can be identified using the same method as above.
5) Excessive load can also cause the fuse to blow, along with increased current draw.
4. After starting, the motor runs slower than normal.
1) A ground fault or turn-to-turn short in the main winding can cause this. Testing methods are similar to those in point 3.
2) Reversed coil connections in the main winding may result in abnormal noise and higher current.
3) If the centrifugal switch fails to disconnect, the auxiliary winding remains energized, increasing current draw.
4) Heavy load or bearing damage can lead to lower speed and higher current.
5) Series-wound motors may experience internal short circuits or poor brush contact, affecting performance.
5. The motor heats up quickly during operation.
1) Turn-to-turn or ground faults in the windings can cause excessive heat. Testing methods are similar to point 3.
2) A short between the main and auxiliary windings (excluding the end connection) can increase current and temperature.
3) If the centrifugal switch doesn’t disconnect, the auxiliary winding stays connected, leading to overheating.
4) Incorrect winding connections in split-phase motors can cause large current surges.
5) Faulty or incorrect capacitance in the working capacitor can also cause overheating.
6) Rotor core rubbing, bearing damage, or heavy load can all contribute to excessive heat.
7) Poor brush contact or internal short circuits in series-wound motors may also lead to overheating.
6. The motor produces loud noise and vibration.
Single-phase motors tend to have more vibration compared to three-phase motors due to an uneven rotating magnetic field. Common causes include:
1) Poor insulation paint causing loose laminations and electromagnetic noise.
2) Damaged centrifugal switches.
3) Worn bearings or excessive axial play.
4) Uneven air gaps or misalignment between stator and rotor.
5) Foreign objects inside the motor.
6) Brush and commutator contact issues in series-wound motors, such as mica protrusion or excessive pressure.
Second, determining if the auxiliary winding or capacitor is faulty and the motor won't start.
If the motor doesn’t start after powering on, and there’s little or no sound, but some current is detected, check the auxiliary winding and capacitor using a multimeter set to R × 1. If the circuit is open, the problem may be in the winding or the capacitor itself.
Without a multimeter, you can manually test the motor. First, discharge the capacitor by shorting its terminals. Then remove the load and try to rotate the motor shaft by hand. If it turns smoothly and accelerates, the issue is likely with the auxiliary winding or capacitor. Further inspection is needed to confirm the fault.
Third, a simple method to determine if a capacitor is good or bad.
Before testing, always short the capacitor’s terminals to avoid electric shock. To check with a multimeter, set it to R × 1k or R × 100. Touch the probes to the capacitor’s terminals and observe the needle movement.
1) If the needle moves quickly to zero and then gradually returns toward ∞Ω, the capacitor is in good condition. The closer it gets to ∞Ω, the better the quality.
2) If the needle doesn’t move, it indicates a short circuit, and the capacitor is damaged.
3) If the needle doesn’t move at all, the capacitor is open and cannot be used.
Alternatively, use a charging and discharging method. Connect a DC power source (e.g., 3–6V battery), charge the capacitor, then discharge it through a wire. A strong spark indicates a good capacitor. No spark means it’s faulty.
Elevator Door Operating System
Elevator Door Operating System,Elevator Mechanism For Hoistway Door,Three Layer Panels,Landing Door Hanger
ZHONG HAN INTERNATIONAL TRADE CO., LTD , https://www.cck-ht.com