DELTA CONNECTION

DELTA CONNECTION

CIRCUIT SCHEMATIC
DIAGRAM	BATTERY +

It is also possible to wire a relay (see diagram 48) which will switch the connections from star to delta and back as desired.

48. USING A RELAYTO CHANGE BETWEEN STAR AND DELTA

BLOCK CONNECTOR

POLE C/ O RELAY (3P2T)

SERIES CONNECTIONS

 

Yet another option for connecting the stator

At the time of writing this document, the above arrangement (using a relay to change the connections) is still under development. Later, an electronic control circuit will be available to automate the changeover. This is all very complex, and it so it can go wrong.

If you do not wish to have to change the connections between low and high windspeeds, then the PMG will still work. However, the efficiency will be slightly less. Three are two options:-

• If you expect mainly low windspeeds, then you can simply use the star connection
shown in diagram 46.

• If you also need higher power in higher winds, you can use a 1 7AWG wire (1 .2 mm
diameter) to wind coils with 200 turns each. Then you can connect one group in
delta and one group in star as shown in diagram 49. Note that you need six AC
terminals on the rectifiers so you will need three rectifier blocks.

49. STAR/DELTA CONNECTION

USE 200 TURNS PER COIL

BLOCK CONNECTOR

BATTERY POSITIVE BATTERY NEGATIVE

PMG-to-Battery Cable size

The cable from the PMG to the battery can be either three-phase-AC or DC. If the rectifier is mounted at the wind generator, then it will be DC. This is only slightly more efficient than three phase AC.

 

At 1 2 volts, the size of the cable must be large. Even if the current is only 1 5 amps, it is advisable to use a heavy cable. For a distance of 20 metres, the recommended size is 6 mm² (1 0AWG). The diameter (thickness) of each copper wire is about 3mm. A 1 5 amps current flowing in this cable will lose 1 5% of the power from the wind generator as heat in the cable. If the cable is longer, it should be heavier, in direct proportion.

Electrical Safety

There is no danger of electric shock from a 12 volt battery. But if the wind generator is disconnected from the battery, and running fast, then the voltage will be higher than 12 volts, maybe as high as 50 volts. Do not run the PMG at high speed without a battery connected.

The battery contains stored electrical energy. When there is a short-circuit fault in the wiring from the battery, for example the positive and negative wires touching each other, this energy is released in a very high current. The cable will heat up and burn. Therefore it is necessary to use a fuse or a circuit breaker on every wire which attaches to the battery positive terminal. Use one fuse for the wind generator and a separate one for the cable to the load (the lights, or whatever uses the power). See diagram 50.

50. CONNECTING THE BATTERY

 

Battery acid is bad for the clothes and the skin. Do not splash it. Be especially careful of the eyes. If there is an accident, the best cure is to flush with plenty of water.

Batteries produce hydrogen gas, which is very explosive. Do not make sparks near a battery or it may explode, and throw acid in the eyes!

Battery Charging

Lead acid batteries should be kept in a charged condition. In the case of a wind powered system, you may have to wait for a wind to charge the battery. But be careful not to discharge the battery too deeply, or to keep it too long in a discharged state, or it will be damaged (sulphated) and become useless. Stop using a battery before it is fully discharged. If there is a problem with the wind generator, then charge the battery from another source within two weeks.

Charging the battery too hard will also damage it. At first, when the battery is discharged, it is safe to use a high current, but later the current must be reduced or the battery will overheat and the plates will be damaged. The best way to fully charge a battery is to use a small current for a long time.

Watch the battery voltage. If the battery voltage is below 1 1.5 volts, then it is being discharged too much. If the voltage is high (over 14 volts) then the battery charging current is too high. Use less current or more current in the loads to correct these problems. If there is no voltmeter available, then the user should watch the brightness of the lights and follow these rules:-

• Dim lights, mean low battery. Use less electricity!

• Very bright lights mean too much windpower. Use more electricity!

A good way to use more electricity is too charge more batteries in windy weather, perhaps charging batteries from neighbours' houses.

There are simple electronic circuits which can regulate the battery voltage automatically. They are called 'low voltage disconnects' and 'shunt regulators'. If the user is not willing to watch the battery voltage, then it is necessary to fit a disconnect and a regulator.