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The use of VSD's (Variable Speed Rives) has become more and more popular. All these have built in current limiters that can be calibrated accoring to the motor current rating. Soft starters have the same function. Alternativley stand alone electronic current limit units can be used. Generally the most cost efficte way in modern systems are VSD units as they are more compact, and not as pricey as the latter two choices. It is not advisable to use a rated curve circuit breaker alone to protect a motor, since the sensitivity and linear tripping time will cause damage to the motor. These circuit breakers are for short circuit protection only or for extended start up curve times. There are also some compact direct online overload/circuit breaker combination unit that is popular for motors under 3 kw, but the function of these is very similar to a conventional overload unit. (Moeller, or Siemens)The best way is a VSD unit, since it the most accurate as well.
