Re: 1937 Voltage Current Regulator Voltage Draw

Posted by HH56 On 2022/9/5 14:12:24

Wire 3B is the BAT connection and is coming from the ammeter. 3A is the armature wire from the generator and 24 is the field wire. 23 is a ground reference wire so the regulator and generator are at the same ground potential and no poor connections between sheet metal or metal to frame connections would affect the regulation..

One question is did you polarize the generator when you installed the new regulator. That is usually a necessary step to get all the charging components attuned to one another and to orient, reinforce and ensure the residual magnetism in the field shoes in the generator is at the proper magnetic polarity depending on how the battery is connected. Polarizing is done by using a short length of fairly heavy jumper wire to momentarily connect the BAT and ARM terminals on the regulator so a surge of current is fed into the generator. The connection is only held for a second or two and there will be a spark when the connection is made. It is mentioned on page 60 in the 37-38 service manual as well as a comment that the cut out relay contacts can be damaged if polarity is reversed or if regulator is disconnected improperly.

The way a typical 2 brush generator/regulator works is when the generator starts spinning, the residual magnetism in the generator field shoes is just enough for the generator to start producing a small voltage and current -- enough to energize the shunt winding in the cut out relay coil and provide enough magnetism to pull in the relay. As soon as the relay pulls in the contacts close which allows full battery voltage to go back into the generator. In a two brush generator the field is also powered from the ARM terminal and the battery will fully power up the field coils. If the generator is one of the third brush variety that brush and how it is adjusted supply the field coil power instead of the battery and the brush will pick up enough current to power the coils. The brush generally serves as a limiting method but has disadvantages in regulation and generators have limited output at higher speeds so the two brush and 3 relay regulator evolved. The overall charging control and cut out relay will still be similar to the two brush type.

Field coils at strength allows the generator to produce increased voltage and current. Once the output voltage and current are strong enough the series winding in the cut out coil strengthens the relay magnet and contact connection and also start working on the other coil(s) in the regulator which causes their contacts to open and close. That action connects either a solid ground or a resistance connected to ground in or out of the field wire. With a voltage on one side of the field coil and the ground or resistance on the other it strengthens or lessens the field to keep the generator voltage and current regulated to the set specification. Set generator voltage specification is usually about 1 volt above normal battery voltage so because it is stronger, that voltage is fed back into the battery and generator is charging. As long as the overall load is within the generator and regulator capabilities and settings the ammeter needle will stay on the charge side.

When the engine shuts off, no more voltage and current coming from the generator allows the spring on the cut out relay contact to pull it open and break the connection to the battery so there should be no discharge back thru the generator or regulator.