Hi guys,
I'd like to share with you some basic rules to select an ESC. Your comments are welcome.
Once you've picked out the motor you will use, you also need to select the Elecrotronic Speed Controller (ESC) that will run it. Thankfully, this task is much simpler than motor selection.
ESCs are primarily rated for the amount of current they can constantly supply to the motor. Some may also have a "burst current" rating, but this should be ignored for now. Determine the maximum current draw from your chosen motor's specifications. Add a 10% safety margin, and look for ESCs rated for at least this amount of current. You will also need to check that your chosen ESC is rated for the correct number of battery cells (usually 3 cells or 11.V) and ensure that it's not too heavy. Once again, any excess weight will be quadrupled, since you need 4 of these items.
Pretty much any ESC will work in your multi-rotor aircraft, but some will work better than others. Some of the higher-quality ESCs are capable of a faster "refresh rate" - the number of times (per second) at which they check for new instructions from the control board and adjust the motor's speed accordingly. A faster refresh rate means finer control, faster response to pilot input and ultimately, greater stability.
The following brands are known to have a fast refresh rate and work well in multi-rotor applications: Turnigy Plush, Mystery and their clones. More recently, the MultiStar ESC range has been introduced, which are designed specifically for multi-rotor aircraft. For what is likely to only be a few extra dollars, getting quality ESCs is an excellent idea and highly recommended.
Be aware that you need 4 identical ESCs for your aircraft. It's possible to make a quadcopter fly with 4 different ESCs, but it will be more erratic and much harder to control.
You might also give consideration to buying a programming card for your ESCs. This small, inexpensive tool will allow you to quickly and easily re-program your ESCs to behave in the correct manner. It's not mandatory - you can program ESCs manually - but the programming card does make things easier.
Hope this helps you and your comments are welcome!