IEC 60947-4-2:2020 pdf free.Low-voltage switchgear and controlgear – Contactors and motor-starters – Semiconductor motor controllers,starters and soft-starters.
Starting characteristics of squirrel cage and hermetic refrigerationmotors
a) One direction of rotation with the inclusion of phase-control capability to provide any combination of controlled acceleration to normal speed, controlled deceleration tostandstill, or an occasional manoeuvre without de-energizing the controller(AC-3a,AC-8a).
b) One direction of rotation with the inclusion of phase-control capability to provide controlled acceleration to normal speed.Controllers and starters are rated for starting and stoppingduty cycles only (AC-3b,AC-8b); for example,after starting, the motor may be connectedinto a circuit that bypasses the semiconductor motor controller or starter.
Two directions of rotation may be accomplished by reversing the connections to the controlleror motor by means that are beyond the scope of this document,but are covered by therelevant product standard for the selected means.
Two directions of rotation may also be accomplished by phase reversing within the controlleror starter.The requirements for this operation will vary with each application.Therefore, thisis subject to agreement between manufacturer and user.
Due to the control capability of controllers and starters, the current during starting,stopping,and any operation will differ from the conventional values of the prospective locked rotorcurrent listed in Table 9.
Starters can be used to provide reduced voltage excitation to the stator windings of a slip ringmotor,and thereby reduce the number of switching steps required in the rotor circuit.Formost applications, one or two starting steps are adequate depending upon load torque andinertia, and the severity of start required.
The power consumption of the semiconductor motor controller or starter may be stated by themanufacturer and is determined by calculating the power losses of the power semiconductorcomponents.
A motor controller consists of two or three power semiconductor controlled phases and thesemiconductor controlling device.These power semiconductors are bypassed or not bypassedafter run up of the motor.
The power semiconductor losses during start-up (and soft stop or braking mode) occur for avery short period of time (seconds) and are therefore not considered.IEC 60947-4-2 pdf download.