Simple Shunt Braking System

Since most of my customers are amateur builders I thought it would be nice to share some low cost ways that I have found to handle over speed wind conditions and storms. 

Before I get into the details of braking lets figure out what kind of motor you have so we will know which type of braking system to use.

Turn the shaft with your hand on your DCPM motor.  Note how easy or hard it turns.  Now hook the two wires from the motor together and see if you can still turn your shaft.  If you cannot turn your shaft this brake system should be able to hold your generator still in most winds.  
If you can still turn it but it is just harder to turn this brake system will only serve to slow down your generator in higher winds, it may or may not be able to prevent damage.
Now with our turn test complete you either have a NO turn or a HARD turn generator.  Keep in mind what your generator is as you read this section so you will know which configuration below you need to use.
Output is different on different generators.  The more output your generator can produce the harder braking you will achieve. After your blades are mounted you can turn the generator again with the two wires contacting and you should be able to tell if this brake system will slow, bring to a slow stop, or just flat slam on the brakes.

Shutting your generator down before a storm is a great idea.  If you know bad weather is in your area or likely, flip the switch to the brake position and wait it out.  That is the best way to handle it.  But what about when you wake up in the middle of the night and find winds of 50 plus?  If you have a HARD turn generator you can just flip the brake switch on and it will at least slow and maybe even stop the generator in due time.
If you have a NO turn generator even with the blades mounted you must use the configuration with the drop resistor or a ballast load such as a light bulb in the circuit.  If you use the configuration without the resistor or bulb and you just flip the switch on, on a NO turn generator you might shear your blades right off at the hub.
That would sink! 
By now you know what your generator needs to use this safety switch.  Use the drawing that fits your HARD turn or NO turn generator.

HARD turn generator
You need 1 single poll double throw switch


Resistor/bulb for NO turn generator
You need 1 single poll double throw switch, and 1 resistor or bulb.

There is an easier option for Dynamic Shunt Braking!

Buy one of my CC-30x Series Charge Controllers and wire it up as shown below.

See the CC-30x Series Charge Controllers.

Return to Tips and Tricks