Electric Flight in Australia


What is a soft start, and what is a brake?

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What is a soft start?
A soft start is starting your motor with reduced current or voltage so that there is not so much strain on your whole system. You start at low power and increase the power gradually.

The bigger your system (i.e. larger motor, more cells, gearbox with large folding prop) the more is the need to have a soft start.

An electronic speed controller gives a graduated soft-start. Basically, such a controller pulses the current to the motor. When the throttle is just opened the pulses are short and rapid. As the throttle is opened more, the pulses become longer and longer until continuous current is fed to the motor at full throttle. This is the most gentle of soft-starts and gives completely proportional throttle control, as well as other advantages, but good speed controllers do not come cheaply!

Why do I have to have a brake on the motor?

A brake is not absolutely necessary, but without one the propeller will free-wheel when the motor is turned off. This will greatly restrict glide time as the propeller acts like a giant air-brake, especially if you are using a giant folding propeller. The brake stops the motor from spinning thus reducing drag, and, in the case of a folding propeller, allows the propeller to fold, which it will not do in the absence of a brake.

An electronic speed controller actively applies a brake onto the motor each time the motor is switched off – typically for 8 seconds – to give the propeller time to fold. Current is actually consumed from the motor pack while the brake is operating, but this is such a small amount as not to be of any great consequence (typically 230 ma for 8 secs = 0.5 ma) but the amount does vary from brand to brand.