IEC 60947-4-2:2011 pdf – Low-voltage switchgear and controlgear – Part 4-2: Contactors and motor-starters – AC semiconductor motor controllers and starters. Periodic duty
Subclause of IEC 60947-1:2007 applies. Duty cycle values and symbols
For the purpose of this standard, the duty cycle is expressed by two symbols, F and S. These describe the duty, and also set the time that must be allowed for cooling.
F is the ratio of the on-load period to the total period expressed as a percentage.
The preferred values of F are as follows:
F=1 %,5%,15%,25%,40%,50%,60%,70%,80%,90%,99%.
S is the number of operating cycles per hour. The preferred values of S are as follows:
S • 1, 2. 3. 4, 5. 6, 10, 20, 30, 40. 50. 60 operating cycles per hour.
NOTE Other valueC aV F andlot S may be declared by the manufaclurer.
5.3.5 Normal load and overload characteristIcs
Subclause 4,3.5 of IEC 60947-1:2007 applies, with the following additions. Overload current profile
The overload current profile gives the current-time co-ordinates for the controlled overload current. It Is expressed by two symbols, X and T.
X denotes the overload current as a multiple of I selected from the array of values in Table 9. and represents the maximum value of operating current due to starting, operating, or manoeuvring under overload conditions. X 1LRPUe when no current limit function is provided.
Deliberate overcurrents not exceeding 10 cycles (for example boost, kickstart. etc.), which may exceed the stated value of X x I, are disregarded for the overload current profile.
T denotes the sum of duration times for the controlled overload currents during starting, operating, and manoeuvring. See Table 9.
For a starter, T is the minimum operating time allowed by the tolerances of the overload relay. Operating capability
Operating capability represents the combined capabilities of
— current commutation and current carrying in the ON-state; and
— establishing and sustaining the OFF-state (blocking),
at lull voltage under normal load and overload conditions in accordance with utilization category, overload current profile and specified duty cycles.
Operating capability is characterized by
— the rated operational voltage (see;
— the rated operational current (see
— the rated duty (see 5.3.4); Starting, stopping and manoeuvring characteristics
Typical service conditions for controllers and starters controlling squirrel cage and hermetic refrigeration motors are as follows: Starting characteristics of squirrel cage and hermetic refrigeration motors
a) One direction of rotation with the inclusion of phase-control capability to provide any combination of controlled acceleration to normal speed, controlled deceleration to standstill, or an occasional manoeuvre without de-energizing the controller (AC-53a, AC58a).
b) One direction of rotation with the inclusion of phase-control capability to provide controlled acceleration to normal speed. Controllers and starters are rated foi intermittent duty only (AC-53b, AC-58b): for example alter starting, the motor may be connected into a circuit that bypasses the power semiconductors.
Two directions of rotation may be accomplished by reversing the connections to the controller or motor by means that are beyond Ihe scope ol this standard, but are covered by the relevant product standard for the selected means.
Two directions of rotation may also be accomplished by phase reversing within the controller or starter. The requirements for this operation will vary with each application. Therefore, this is subject to agreement between manufacturer and user.
Due to the control capability of controllers and starters, the current during starting. stopping, and any manoeuvre will differ from the conventional values of the prospective locked rotor current listed in Table 11. StartIng characteristics of rheostatic rotor with controllers energizing the stator (AC-52a, AC-52b)
Starters can be used to provide reduced voltage excitation to the stator windings of a slip ring motor, and thereby reduce the number of switching steps required in the rotor circuit. For most applications, one or two starting steps are adequate depending upon load torque and inertia, and the severity of start required.
NOTE Starters and cont,oliers covered by thie standard are not Intended lot us. In the rotor circuit and therefore. the rotor circuit must be controlled by traditional means. The relevant product standards for the rotor CIrcuits 04 rheoslatic rotor starters should apply
5.3.6 Rated conditional short-circuit current.