Building a 1 kW automotive voltage regulator

[GerCer]

Hello, I have a project at the university, i need to build a 1kW voltage regulator that can be used in cars. I did some search trying to find actual car circuit designs but couldnt find any good design. I did find a but it doesn't meet the 1 kW requirement. I was thinking to use some transistors to insert more Amperes into the output. I made a simulation in Proteus using a LT3010 voltage regulator and put some transistors. I was wondering if someone has a circuit you could share or giving me some tips to find the right components for this project.

This is my first ost so i don't know what kind of info i could be sharing with you.

Thank you

 

[Sunnysky]

• as in any design, start with a list of specs.;

• Vin min-max
• Vout tolerance, load regulation, input regulation.
• Load type.
• Start surge current limit.
• efficiency min.

Experience, budget, timeline.

Is this intended to be just the regulator inside/for the alternator?
Then it is different.

Define all input/outputs and parameters, indicators, controls.
Then objectives
then research

e.g. http://www.onsemi.com/pub_link/Collateral/CS3361-D.PDF

 

[Bluejets]

Most car alternators these days run at around 80A so I don't see any problem getting one there.

 

[debe]

This is a circuit that will power an 80A 14V Bosch altenator, It uses PWM & the CRO pics are across the Field winding.

 

[GerCer]

Thank you for the replies.
So first of all i don't have any experience making this kind of regulators. I built some regulators using LM317 some months ago. I have enough budget for the project so that wouldn't be a problem. Timeline is 5th august.

Specifications:
The stator gives up to 80V.
The output must be 12V
Potency should be 1kW
There will be a battery, alarm, horn, ECU, lights and a motor.
The regulator should be directly to the stator.

I tried to find linear voltage regulators (i thought that would be the easiest way to do this) but those that I found doesn´t provide the current needed.

 

[Sunnysky]

Thank you for the replies.
So first of all i don't have any experience making this kind of regulators. I built some regulators using LM317 some months ago. I have enough budget for the project so that wouldn't be a problem. Timeline is 5th august.

Specifications:
The stator gives up to 80V.
The output must be 12V
Potency should be 1kW
There will be a battery, alarm, horn, ECU, lights and a motor.
The regulator should be directly to the stator.

I tried to find linear voltage regulators (i thought that would be the easiest way to do this) but those that I found doesn´t provide the current needed.

LDO? No, not , never.

First understand how an alternator works by amplifying field current with moving rotor and then see how voltage ...regulator controls field current to correct the output rectified voltage.

Then review my MOT IC link and @debe's suggestion until you understand how both work. Dont stop until you understand.,and assume alternator is like a big variable frequency current gain amplifier except outputs 3 phase current for lower rectified ripple.

 

[Chemelec]

Even though most say it is 12 Volts, the Alternator output is usually between 14 to 14.6 Volts, so it can charge a 12 volt battery.

This regulator works good and runs cool.
http://chemelec.com/Projects/Alternator/Alternator-Reg.htm

 

[Sunnysky]

@GerCer Alternator rgulators are required to do more than charge batteries. There must be temperature regulation to prevent over-charging and deep sulphation as well as surge dump protection and field short circuit protection from causing max current output.

• 80 V Load Dump
• Temperature Compensated Regulation Voltage
• Shorted Field Protection Duty Cycle, Self Clearing

I suggest you add these to your requirements.

Also consider that a good battery at low SoC represents a very low ESR, not quite a short circuit, so your regulator must consider how to limit the charge current to protect the alternator from several hundred to 1k Amp peak currents depending on alternator.
Most returned Alternators are recycled/ refurbished due to blown diodes, are about 1% of the cost of an alternator in vol.

 

[GerCer]

I was reading the links you sent me and there are some stuff I don't understand, I hope you can help me out.

1.- In the different designs, the battery is directly connected to the diode bridge, I understand that the reason is that the stator provides all the current needed. The battery are supposed to reach around 14V while the car is on and I can't understand where all the voltage from the stator goes. Does that means the stator will give around 14V all the time?

2.- @Chemelec: In the circuit you posted, the Output should be connected directly to the battery or where else i should connect it?

3.- This is the part where I'm stuck now in the design because I was looking at the alternator and I couldn't see the field wire, just the 3 yellow wires of each phase.


Sorry if I take some hours to answer, I like to read what you post and do a little bit of research to understand better before I reply.

 

[duke37]

Early auto alternators had the control circuit external to the alternator, more recent ones have the control inside.
The rotor has current applied to give the correct output voltage.
The alternator has to run at various speeds and a cunning method is used to enable this. There is built in leakage inductance which has an impedance proportional to speed so even though the voltage is high at high speed, the impedance is also high so the current is limited. The inductive impedance is lossless.

 

[Chemelec]

CerCer: I usually recommend to connect it to the Alternator Output.
Because of Voltage Drops between the Alternator and battery, this will result in a slightly Lower Voltage of charging, Especially at High Currents.

Look at the picture overlay for these connections.