Hand AC and DC generator (physics lab instrument)

1,Hand generator provides the demonstration of the construction and operation principle
2, Also used as a small power supply

1.Application 

The J2417 model hand AC and DC generator mainly provides the demonstration of the construction and operation principle of an AC and DC generator for teaching the physics for junior middle schools and the natural science for primary schools. It is also used as a small power supply.

 

2. 

The generator mainly consists of a stator, a rotor, brushes, a turning mechanism, a collect ring (or a communtator), a small bulb holder and a base plate.

  

Fig.1. the composition of the generator

 

3,Operation principle

 The generator is a permanent—magnet rotating armature generator. When the armature coil rotates in the permanent magnet field, the induced electromotive force will be generated by the coil cutting the mage tic line of force.

Because the direction of the cutting is a periodic change, the direction and amount of generated induced electromotive force varies as the periodic change, generating an alternating current.

The alternating current by the armature coil is received in the external circuit through the brush output in the collector ring (commentator); and the direct current through the brush output in the commutator (half ring part).

4,Specifications

 (1) Output idle voltage: AC and DC idle voltage≥8V at 1200-1600 rpm rotating speed of rotor.

(2) Output load voltage: Load voltage≥5V at 1200-1600 rpm rotating speed of rotor and connecting 4.8V, 0.3A small bulb.

(3) When the two brushes of the generator are put in the two ends of the commutator, the output is an alternating current. When they are put in the middle of the commutator, the output is a direct current.

(4) Distance between rotor and pole piece≤1.5mm, without collision and friction

(5) Operation performance: At turning the handwheel for two minutes, no slide and loose belt; no deformation and shift brush; normal generation.

5, Operation

 (1) Adjust the brush and the collector ring (commutator) before the operation and keep good contact. When turning the handwheel, the bulb will come on, indicating normal generation. Then an experiment will be done when desired.

(2) 

Fig. 2

AC generator: Its circuit is shown in Fig. 2. Place the brushes at the two ends of the commutator, and then connect a slide rheostat with a large electric meter for demonstration as shown in Fig. 2. Turn the armature slowly, and the current meter will have two direction indications continuously, indicating an alternating current.

 (3) DC generator: When place the two brushes in the middle of the commutator, keep the external circuit constant and turn the armature, and then the needle of the current meter only will have one direction indication, indicating a direct current.

6,Maintenance and trouble shooting

  (1) The brushes and the commutator should keep cleanness and good contact. The pressure of the brushes on the commutator should keep suitable degree of tightness.

(2) Because of a very small gap between the rotor and the pole piece, you should inspect the block condition when in use. If the block exists, you can adjust the support position. Properly add Lubrication oil at the bearing to reduce friction and noise.

(3) The polarity of permanent magnet should be put in the heteropolar position, or the current will not be generated.

(4) All lines should be connected properly.

7,Points to watch

   (1) The generator is for teaching demonstration. It is used only by hand and is not permitted with other power drive.

(2) After the experiment, the belt should be removed to avoid elastic fade.

(3) When not in use, the generator should be kept in the dry and ventilation place to avoid moisture.