This article begins with an explanation of the principles of motor start capacitors, then details the phenomenon of failure, causes, and test methods for the two common household appliances, air conditioner and fan start capacitors. If you want to know the relevant knowledge of motor starting capacitors, it is worth reading this article.
Three-phase AC motor and a single-phase AC motor key differences? If you pay attention to this, you can see that the single-phase AC motor has more equipment than the three-phase AC motor, which are the motor start capacitors (starting capacitor). The most common are a variety of household appliances. Starting capacitors are installed in almost all household appliances with motors.
The principle and causes of damage to the starter capacitor
How does the engine work?
Single-phase current flowing through a single-phase motor cannot generate a rotating magnetic field and requires a phase-separation capacitor. The purpose is to ensure that the currents in the two coils generate a phase difference of about 90°C to create a rotating magnetic field.
Capacitive induction motors have two coils, a starting coil and a traveling coil. The two coils are spaced 90 degrees apart. A large capacitor is connected in series with the starting coil. When the moving coil and the starting winding carry single-phase alternating current, the current of the starting coil is 90° ahead of the moving coil current due to the action of the capacitor, so the maximum value is reached first.
Two magnetic fields identical in time and space are formed so that a rotating magnetic field is created in the air gap between the stator and the rotor. An induced current is created in the rotating part of the motor, and this current interacts with the rotating magnetic field, due to the influence of the rotating magnetic field. The torque of the electromagnetic field causes the motor to rotate.
How does the motor start capacitors work?
Single-phase power sources differ from three-phase power sources in that they generate a three-phase rotating magnetic field in the motor.
The principle of operation of a capacitor in a single-phase motor is as follows. Using the principle that the current of the capacitors in the circuit travels 90 degrees, a magnetic field of 90 degrees is created before the primary winding in the starting coil. The motors rotate at an angle of 90 degrees. Simply put, the magnetic field uses the principle of phase displacement of a capacitor to convert single-phase power supplies into two-phase power supplies at 90° to each other, each transforming a 90° rotating magnetic field. Others are generated by the engine.
Perhaps it is easier to explain this aspect. The starting capacitor is to give thrust to the motor when it starts, allowing the motor to spin from transition to rotation. Without it, when a single-phase AC motor starts, it originally oscillates rather than spinning. Since the starting capacitor is a two-phase AC motor, the magnetic field cannot exert a force on the rotor without it, and of course it cannot rotate.
Reasons for combustion of the starting capacitor
In general, the motor start capacitors have a very short operating time, so they are difficult to burn and are released by a centrifugal switch during starting, so no current flows through the starting capacitor. However, the difficulty of burning does not mean that it will never burn.
If the starting capacitor burns out, the possible causes are:
Capacitors have a low tolerance voltage or poor quality, so it is better to use a capacitor with a voltage of 500 volts.
when the centrifugal switch is turned off arcs often occur. You can burn the key on the engine. After starting the switch, you cannot turn it off. Current always flows through the capacitor. The secondary winding of the motor and the starting capacitor burn out easily within a certain period of time.
The capacitance of the selected capacitor is very small and the starting current exceeds the tolerance of the capacitor.
The motor is dull or the bearings have been damaged. It is difficult for the motor to start the centrifugal switch within a certain period of time, it is difficult to reach the cutting speed, and the starting capacitor is easy to burn out.
Air Conditioner Start Condenser Troubleshooting
Functional characteristics of the starting capacitor
The starting capacitor is an important part of the auxiliary operating compressor. The capacitor is a large capacity capacitor (1 to 6 uF) that supplies the starting current to the auxiliary coil of the motor and helps start the compressor. the bracket or support plate above the compressor have the motor start capacitors usually installed on them.
to the starter end of the compressor has the pins attached to it.
How to quickly detect damage to the start-up capacitor
First, it depends on the type of capacitor used in the electrical components.
- Starting of the compressor: If the condenser is damaged, the compressor cannot start or run intermittently .
- If the fan motor capacitor is damaged, the exhaust temperature may be too high, the exhaust pressure may be too high, the compressor may be overloaded, or the air volume may be low while the air conditioner is running.
Why is the starting capacitor of the outdoor unit of the air conditioner easily damaged?
The outdoor unit has air conditioner compressor condenser connected. Because the outdoor unit has a high temperature (ambient temperature + discharge temperature from the capacitor), the capacitor used for a long period of time tends to dry out, and the electrolyte will break down.
Always use high quality capacitors when replacing them. The capacitance should be the same and the withstand voltage should not be lower than the original standard.
Symptoms and test methods
- It is not working properly.
- It cannot be displayed normally.
- It is not possible to normally charge and discharge the power supply.
- It cannot be heated normally.
The power factor compensates for damage to capacitors and waste of energy.
Various symptoms of damage to the compressor start capacitors and external engine start capacitors:
There are two capacitors in the external electromechanical package, the largest is the compressor capacitor and the smaller is the external motor capacitor. Different capacitors have different failure phenomena.
compressor capacitor damaged
Performance symptoms are that the normal start-up of the compressor is accompanied by severe noise and jitter. If the capacitor is damaged, pressing the casing on top of the compressor will cause the compressor to feel a slight amount of jitter, which will look like an electric current is flowing through it. The compressor will stop working after a while.
External motor capacitors damaged
After the compressor runs normally, the outboard motor will stop working for a certain period of time. If there is a fault code, there is a high pressure protection and a compressor exhaust pipe temperature protection.
Air conditioner start condenser test method
The air conditioner compressor starting capacitor is a large capacity electrolytic capacitor. When testing, use the amplitude setting of the digital multimeter to check for any anomalies.
Under normal circumstances, the capacitance of the capacitor used to detect the capacitance of the multimeter should be equal to or very close to the nominal capacitance. If not, then the starting capacitor must often degrade, with dry electrolytes, leaks, etc. Please exchange.
The second method:
In addition to testing the capacitance with a multimeter, you can also use the ohm setting of a multimeter. The indicator to test the charging and discharging performance of the starting capacitor.
- Connect the red and black test leads to the poles of the compressor start capacitors.
- The multi gear has Ohm gear set.
- Under normal circumstances, the multimeter pointer first swings to the right to move to the position, then slowly to the left, and finally stops at a fixed position.
- If the indicator does not oscillate or the oscillation range is narrow, this indicates that the compressor starting capacitor is working poorly.