Force alternator to supply current only in 1 direction

Thread Starter

G0dsp33d888

Joined Jun 4, 2018
8
I have searched all over and have not found an answer. I am a newbie, please bear with me, I'll try to explain as best as I can.

I have an alternator which I assume has a 3 phase wye configuration. I am planning on removing the rectifier. I would like the alternator to supply power when it is spun in 1 direction and cease power when it is spun in the opposite direction. Is there a way for the phase sequence to enable and disable the current flow?

Thank you very much for all your help!
 

shortbus

Joined Sep 30, 2009
9,375
The alternator will be a delta format and will produce AC power in both directions, the only way to stop it will be to remove the rotor field power when it's reversed.
Depending on the type of alternator it may still produce some output though, just not at the same level that an energized rotor would. Most car alternators have some residual magnetism but we don't know what type of alternator is used in this question.
 

Thread Starter

G0dsp33d888

Joined Jun 4, 2018
8
The alternator will be a delta format and will produce AC power in both directions, the only way to stop it will be to remove the rotor field power when it's reversed.
Thank you for your reply. Do you know how I would be able to remove the rotor field power based on rotation direction?
 

Thread Starter

G0dsp33d888

Joined Jun 4, 2018
8
One way for sure would be to sense rotational direction and use it to drive a relay. What is your ultimate goal with this question?
I was ultimately trying to design a piece of workout equipment that would have resistance going one direction, then no resistance the other. Upon applying voltage to the rotor field I found that it was not as much resistance as I thought it would be.

Sorry to waste everyone's time. Is there a way to delete this thread?
 

RPLaJeunesse

Joined Jul 29, 2018
213
Motional resistance is a function of the load on the alternator. Keep the diodes and use an adjustable DC load device (solid-state load as used to test a power supply) to vary the forward direction loading. Sense phases before the diodes for direction information. Search for "phase sequence detection circuit" and pick a suitable one. Adapt it to the expected alternator output level, use the correct rotation to enable the solid-state load.
 

MrSalts

Joined Apr 2, 2020
1,762
I was ultimately trying to design a piece of workout equipment that would have resistance going one direction, then no resistance the other. Upon applying voltage to the rotor field I found that it was not as much resistance as I thought it would be.

Sorry to waste everyone's time. Is there a way to delete this thread?
A dc motor could be used. When the leads are shorted together, the motor is hard to turn (harder with high force and less resistance at lower force applied). If you can come up with an electric or mechanical way to disconnect the leads, the motor will spin freely in the other direction.
 

Thread Starter

G0dsp33d888

Joined Jun 4, 2018
8
Motional resistance is a function of the load on the alternator. Keep the diodes and use an adjustable DC load device (solid-state load as used to test a power supply) to vary the forward direction loading. Sense phases before the diodes for direction information. Search for "phase sequence detection circuit" and pick a suitable one. Adapt it to the expected alternator output level, use the correct rotation to enable the solid-state load.
Wow this sounds like the solution! Thank you so much!
 

PaulNewf

Joined Mar 24, 2020
16
How about a diode across a DC Motor so it only shorts in one direction, and possibly a variable resistor in series with diode to vary the drag. Diode and resistor need to be chosen for the generated power. Sticking with the car parts source... Many DC motors (starter, wipers, windows, fans), and there are heavy duty diodes and variable resistors in there somewhere too.

Ensure diode reverse voltage is several times the motor voltage as there will be voltage spikes, maybe 100V to 1000V for reliability.
 

PaulNewf

Joined Mar 24, 2020
16
Alternator: possibly a half bridge rectifier instead of a full bridge could make it directional, or toss the rectified and just try a diode across a single winding as a test.
 

RPLaJeunesse

Joined Jul 29, 2018
213
Alternator: possibly a half bridge rectifier instead of a full bridge could make it directional, or toss the rectified and just try a diode across a single winding as a test.
How would / could this work? Any alternator winding will produce a full sine wave irrespective of rotational direction.
 
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