Diesel generator maintenance training diesel article -p81-p85 electric starting system and instrument...

Diesel generator maintenance training of the diesel engine -p81-p85 electric starting system and instrumentation seventh section electric starting system and instrument

When the diesel generator diesel engine is in a stationary state, the diesel fuel in the fuel system cannot be sprayed into the combustion chamber in a mist. The gas distribution system cannot complete the normal intake and exhaust of the diesel engine. Therefore, if the diesel engine is to enter the self-running state, it must be supported firstly. external force. At present, a single-cylinder diesel engine generally uses human power to crank the crankshaft so that the diesel engine enters a starting state. A cylinder or a large-powered diesel engine is generally started by means of a starter, compressed air, or a small diesel engine. This section mainly introduces the electric starting system.

The electric starting system is mainly composed of a starter, a battery, a charging generator, a charging generator regulator and a meter. The role of the starting system is to overcome the starting resistance of the diesel engine, so that the diesel engine from the static state into self-running state.

First, the composition of diesel generator starter

The physical appearance of the starter is shown in Figure 2-106. The starter is mainly composed of a DC motor, an electromagnetic switch, and a drive mechanism inside the housing. Its role is: The battery as a power source to drive the rotation of the diesel engine crankshaft, the diesel engine into its own operating state.

1. DC motor

The crank DC motor used in the diesel generator starter is a series-excitation DC motor rated for a short time. The starting DC motor is different from the ordinary DC motor because it can generate a large torque, so the use of the current is particularly large, and the starting circuit of the wire is also relatively thick. In general, the start time of the starter must not exceed 12S.

The DC motor is mainly composed of an armature, a commutator, a magnetic pole, an excitation winding and a brush. The armature winding and the excitation winding inside the housing are connected in series. When the battery supplies power, the excitation winding and the iron core form a magnetic pole to generate a magnetic field, and the armature winding also generates a magnetic field. The two magnetic fields interact with each other to generate a large torque, and then decelerate the gear output power.

2. Diesel generator set electromagnetic switch

The physical appearance of the electromagnetic switch (or magnetic switch) is shown in Figure 2-109. The electromagnetic switch is a device for turning on and off the main circuit of the starter motor. When the direct current and the electromagnetic switch are connected, the sucking coils and the holding coils inside the electromagnetic switch generate a strong magnetic field. Under the action of the magnetic force, the shift fork pushes the driving gear to the diesel flywheel and meshes, and the electromagnetic switch is internally The movable contacts are in contact with the two terminal contacts so that the main circuit of the starter is switched on. When the direct current and the electromagnetic switch are disconnected, the drive gear returns to the original position under the action of the return spring, and the starter stops the IL operation when the time comes.

Magnetic switch dynamic contact and static contact (see Figure 2-110) in the long-term work process (especially in winter, the diesel engine is difficult to start) prone to burning. When the contacts are burned, it will cause the starter gear (or flywheel) to hardly mesh with the flywheel gear ring of the diesel engine. The prone to failures are: First, can hear the high-speed rotation sound of the gear (or rejection wheel), but the diesel flywheel does not rotate; Second, the diesel engine can start, but the starter gear (or rejection wheel) can not return and with the diesel flywheel Turning together, causing the starter to burn out: The third is to hear the gear (or thrown wheel) and the diesel flywheel gear ring impact sound, but the diesel flywheel does not rotate. The above-mentioned Z-type fault phenomenon is generally caused by burning or sintering of a movable contact and a stationary contact of a magnetic switch.

When the above three phenomena occur in the magnetic switch, the two solder joints of the magnetic switch should be welded with a 20kw electric iron according to the method shown in Fig. 2-111. Tighten the fixing screw and remove the movable contact and static contact. Click and then polish the two contacts with fine emery cloth or suede sandpaper.

Before the magnetic switch is assembled on the starter, the armature should first be fixed on the fork of the starter, and then the magnetic switch should be assembled, as shown in Figure 2-112 and Figure 2-113.

3. Diesel generator set drive mechanism

The internal drive mechanism of the starter is shown in Fig. 2. 114. It is mainly composed of a drive gear, a spiral sleeve, a spring, a slip ring, a shift fork, and a lock nut. Its role is: in the instant of starter motor and DC power, the use of electromagnetic force and spring force make the gear mesh with the diesel flywheel and make the gear rotate at high speed; at the moment of disconnection of starter motor and DC power, the gear can return The location of the original beam.

The vulnerable components of the internal drive mechanism of the starter are shown in Figure 2-115 and Figure 2-116.

The prone to failure of the drive gear is the sliding of the head of the gear teeth and the slipping of the outer drum. The main reason for the above-mentioned component damage is excessive wear due to long-term running-in with the flywheel ring gear. After the component is damaged, the new gear (or spin-off wheel) is directly replaced without repair.

The distance between the two shift levers of the shift fork increases due to wear, so that the gears cannot mesh with the flywheel ring gear, causing the diesel engine to fail to start. The fault phenomenon is: When the start button is pressed, the sound of the starter gear rotating at a high speed can be heard, but the diesel flywheel cannot rotate. After the distance between the two levers is increased or the bumps are polished, the starter can be removed and the forks removed for compression or welding repair.