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KR200 Electrical System Overview PDF Print E-mail
Written by Robert Soditus   
Saturday, 24 July 2004

When the engine is stopped and the ignition switch turned on, the battery supplies power to all circuits.
Turning on the start switch energizes the start relay. Heavy duty contacts of this relay will supply high current to the stator coils, which are in series with the rotor by way of, HE of the reverse relay (which is de-energized as shown in the forward start position), B1, the rotor, B2 and ground. This is a series connected DC motor which has the characteristic of a very large amount of torque at low RPM's.

After the engine starts and the ignition switch is released, the starter relay deenergizes. The stator coils are out of the circuit and from this point on the system operates like a DC generator. This DC generator supplies voltage and current to all electrical components in the car and charges the battery when the engine is running. The generator voltage must be controlled because a high generator voltage will result in a high generator output current. Too high of a generator voltage will cause light bulbs to burn out, fuses to blow, overheat the coil and overcharge the battery causing battery water to boil away. Generator output voltage is controlled by the voltage regulator relay.

One side of the generator field coil is connected to the rotor through HE and B1 of the reverse relay. The B2 side of the rotor is grounded by the reverse relay as is the DF side of the generator coil through normally closed contacts of the regulator relay. This puts the generator field coils in parallel with the rotor creating a "shunt wound" generator that is driven by the engine. The output voltage of a shunt-wound generator is more constant than that of a series wound generator but will still increase as RPM's increase.

The voltage regulator controls the generator voltage output by controlling the current in the "generator field coils". Increasing field current generates a stronger magnetic field which results in a higher generator output voltage. Decreasing the current, produces a lower output voltage. The DF side of the generator fiels coil is grounded through the normally closed contacts of the voltage regulator relay.

When the engine starts and is running at low RPM, the regulator relay contacts are as shown on the diagram. As engine RPM's increase, the generator output voltage will increase. This voltage is applied to the voltage cutout relay and the voltage regulator relay trying to energize both relays. (The voltage cutout relay would be more properly called the "charge circuit connecting relay). The voltage cutout relay will operate first when the generator output reaches 12.8 volts. Its contacts will connect the battery charging circuit (through the blue coils), to terminal 51/30 and the battery. The current flowing in these coils is the battery charging current.

Since generator voltage is greater than 12 volts, current will now be flowing into the battery and the battery will now be charging. (The charging current through the blue coil on the voltage cutout relay will add to the magnetic field to help keep this relay energized). When RPM's increase and generator output reaches a voltage between 13 and 13.5 volts, the normally-closed contacts of the voltage regulator will open but will not fully transfer to terminal 61/D+. At this point, the ground is removed from the DF side of the generator field coil and a 6 ohm resistor is placed in series with it. This will reduce the generator output voltage by about 10%. This (normally closed) regulator contact will be opening and closing when the generator output varies between 13 and 15.5 volts to limit the charging current to the battery.

As engine speed increases, the generator output reaches 15.5 volts. Now the battery charging current becomes too high and excessive current could overheat the generator field coil and the voltage could possibly damage other electrical components. At 15.5 volts, the regulator relay contacts transfer completely across and connect DF to 61D+ and HE. This will "short out" the generator field coil and the generator output voltage will drop to zero volts. At this point, both the voltage cutout and voltage regulator relays will de-energize and disconnect the charging circuit. (blue coils). Now the whole procedure repeats giving us a charging current with over-charge protection.

When the generator output voltage is higher than the battery voltage, the charging current in the "blue coils" will try to keep both relays energized and current is flowing into the battery. If the generator voltage is less than battery, the current is reversed in these coils which will help to de-energize the relays and open the charging circuit when the cutout relay de-energizes. This insures that the battery is not supplying current to the generator field coil when the generator voltage is low. (This would happen when the generator output drops to 11 volts or 8 volts or even lower.)

With the engine running at low RPM's, the generator produces a low voltage at "HE". This low voltage is connected to one side of the Charge Lamp. The other side of the lamp is connected to the battery through the "Run Switch". The charge lamp will be illuminated until the generator output voltage starts increasing and then the lamp will begin to dim. When the generator output voltage reaches 12 volts, there will be no voltage across the lamp and it will be completely extinguished. When the generator output reaches a maximum of approximately 15 volts, there will only be 3 volts across the lamp which is not enough to illuminate it.

The only maintenance that could be performed is cleaning of the relay contacts. Contacts may be dirty or slightly pitted due to continual operation and sparking. DO NOT use a file, sandpaper or emery paper to clean the contacts. The bset way to clean them is to use a "contact burnishing tool" which may be found at an electrical supply store. This is an almost smooth metal blade that is inserted between the contacts and rubbed to polish them smooth. This will remove any dirt or small burrs on the contacts. If you can't find a burnishing tool, you can use "crocus cloth". This is an emery cloth impregnated with a material like "red jewelers rouge" that will clean and polish the contacts without scratching them.

This is the easiest part of all. On the SIBA regulator there are no adjustments. However, if you want to make adjustments, you need a 12 VDC power supply that you can vary the output. With the regulator on the bench, apply +12 volts to terminal 61/D+ and the grounded case. When you increase the voltage to 13 or 13.5 volts the normall closed contact should open. It is possible to gently bend the normall closed contact so that the arm of the contact opens at this voltage. Further increasing the voltage to 15.5 volts should move the arm over to connect to the normally open contact. This contact can be bent to operate at this voltage. The cutout relay contacts should close at 12.8 volts.

For anyone wanting to install an Ammeter, all that is necessary is to disconnect the heavy copper wire from the top blue coil to terminal 51/30 and connect it to the Ammeter. This would mean adding an insulated terminal to the voltage regulator box. The ammeter would now measure current flowing into and out of the battery but not the starter current. I have installed an ammeter but the only units I could find was 0 to 30 amps. What I really wanted was a zero to plus and minus 10 amps. After many attempts to make a low resistance meter shunt (.000?? ohms) by paralleling small resistors I found an easy way. I took a length of heavy guage wire, formed it into a coil, and attached it across the ammeter terminals. I don't know how accurate it is and don't really care. It just shows me when the battery is charging and when it is discharging.

Any comments, suggestions or corrections would be appreciated.
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Last Updated ( Monday, 06 October 2008 )
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