1610D Volt Reg Wells VR728 no joy

[WhiteRock]

<font color="blue">With no battery the full rectified alternator output would be across the eb junction of Q4, Z1, and D6. </font>

With no battery I thought we determined that the SCRs could not fire, therefore this circuit could not load up because D6 has no return to the alternator. Correct?

 

[reb]

You are right. I originally thought a path across the SCRs was necessary to provide a path for the base current of Q3 during normal operation. More thought has convinced me that is not correct. The battery provides the path for that current. Therefore, assuming I haven't missed something else, the bridge rectifier is off at all times when there is no battery connected. No voltage is provided at the output without a battery.

 

[evofxdwg]

Wow - looks like i started a profound technical argument!. I started looking at the same question the other night and almost went blind trying to reverse engineer the actual circut from the unit i have un-potted. I gave up due to time and fatigue. But I can tell you there ARE many more components in the circuit than are shown in that schematic. Several bias resistors, some bypass caps, and other protection diodes. If i didnt make a mistake, there are two (10K, 1k? not real sure if its orange or red) resistors from the two AC lines to the SCR gates that would keep them OFF unless Q3 overcomes the bias (through some other resistors and protection diodes not shown). Of course if i erred and these SCR bias resistors come from opposite sides of the AC, it would turn them ON in the absense of Q3 control!

I was about ready to argue the diode leakage would get the Q4/Q5 conduction "started" without a battery until i found the SCR "reverse bias" resistors.

Here's a Thomas Edison solution:
Anybody got a working tractor with this regulator? Go start it up, then turn ignition off (leave motor running), then disconnect battery, then disconnect/reconnect regulator (just to make SURE it turns off), then turn ign switch on, and turn lights on - if electricals/lights work, the circut is "self starting."

 

[reb]

evofxwd:

I sent you a PM this pm.

reb

 

[evofxdwg]

and i replied via PM
sorry for the multiples - i didnt realize the "continue" button sent it as i was editing. Just delete all but last with subject "volt reg"

 

[Paul_M]

I agree that there are missing bias and stability components, but basic circuit operation is simple: Q3 supplies gate current to SCRs. When battery voltage rises above Vz plus 2 Vbe (Q4 and D6), Q4 shuts off Q3. This scheme delivers mostly integral half cycles of current, since SCRs stay on once turned on. This is important, since alternator must not be magnetized by net DC current. Also, current limiting is partly accomplished by copper resistance and partly by inductance of the alternator, which has a rising effect as engine RPMs (hence alternator frequency) increase.
A common cause of regulator failure is poor battery connections, which can allow system voltage to rise to destructive levels. If you're not using your lights, the alternator has no other load besides the battery.
Paul Mathews
Yanmar Ym1610

 

[mark777]

Paul, Welcome to TBN

The thread you responded to is a little old...but it's alway good to have another view on Yanmar electrical, from an owner of a Yanmar.

Mark

 

[evofxdwg]

hanks Paul M for chiming in.

I didn't think about possible magnetization of the rotor due to DC bias. But it makes sense. I will put this in my "circuit development requirements."

I have been casually looking around for a simple (low component count) alternate design that would be cheaper than the OEM replacement part, and hopefully more reliable. One of the problems is the dynamo (?not sure of the proper term for a single phase alternator) outputs 13.4V to 35V RMS AC (close to 50V pk when rectified) over the usable RPM range. The application begs for a Low Dropout device at the low end combined with wide input range, and up to 5A output.

An LM338 3-terminal regulator reqires input V to not exceed output by more than 10V.

I have looked at DC-DC convertors (combined with a full wave rectifier) but haven't found a simple circuit that will do the job and is also cheaper.

I still haven't replaced my 1610D limiter. I just put a battery maintainer on it once in a while. My regulator rebuild project is sitting in a box waiting for me to get around tuit.

 

[evofxdwg]

I ran across this old thread and decided to give a final update. A few months after my last post, i ordered the replacement regulator/limiter (whatever folks want to call it) unit from Hoye and installed it. I realized i dont have the time to dedicate to a redesign. Its now 2016 and the replacement still works fine.