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10/18 ABB MOTOR PROTECTION AND CONTROL

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Standards and utilization categories

Utilization categories:
A contactor's duty is characterised by the utilization category together with the rated operational voltage and current
indicated.
Utilization categories for contactors according to IEC 60947-4-1:
Alternating current: AC-1 Non-inductive or slightly inductive loads, resistance furnaces.
AC-2 Slip-ring motors: starting, switching off.
AC-3 Cage motors: starting, switching off running motors.
AC-3e Cage motors with higher locked rotor current: starting, switching off running motors.
AC-4 Cage motors: starting, plugging, inching.
AC-5a Discharge lamp switching.
AC-5b Incandescent lamp switching.
AC-6a Transformer switching.
AC-6b Capacitor bank switching.
AC-8a Hermetic refrigeration compressor motor control with manual resetting of overload releases.
AC-8b Hermetic refrigeration compressor motor control with automatic resetting of overload releases.
Direct current: DC-1 Non inductive or slightly inductive loads, resistance furnaces.
DC-3 Shunt motors: starting, plugging, inching, dynamic breaking of DC motors.
DC-5 Series motors: starting, plugging, inching, dynamic breaking of DC motors.
DC-6 Incandescent lamp switching.
Utilization categories for contactor relays according to IEC 60947-5-1:
Alternating current: AC-12 Control of resistive loads and static loads with opto-coupler isolation.
AC-13 Control of static loads with transformer isolation.
AC-14 Control of weak electromagnetic loads (≤ 72 VA).
AC-15 Control of electromagnetic loads (> 72 VA).
Direct current: DC-12 Control of resistive loads and static loads with opto-coupler isolation.
DC-13 Control of DC electromagnets.
DC-14 Control of DC electromagnets having economy resistors.

In fact some applications, and the specific criteria characterizing the various loads controlled by contactors, may modify the
utilization characteristics of the contactors. The main applications concerned are:
Capacitor bank switching
Account must be taken of high peaks when the current is made and of harmonic currents during continuous duty. For this ap-
plication, IEC publication 60947-4-1 stipulates utilization category AC-6b. The operational currents or powers acceptable for
the contactors are determined by our electrical tests; IEC publication 60947-4-1 gives the calculating formula for determin-
ing the operational current (Table 9).

Transformer switching
Account must be taken of the peaks due to magnetization phenomena when the current is made.
For this application, IEC publication 60947-4-1 stipulates utilization category AC-6a. The operational currents or powers ac-
ceptable for the contactors are determined using the values obtained for AC-3 or AC-4 category tests and the calculating for-
mula given in IEC 60947-4-1 (Table 9).
Lighting circuit switching
The current peaks occurring on energization of the circuit and the power factor depend on the type of lamps, the connection
mode and whether or not there is compensation.
For this application, IEC publication 60947-4-1 stipulates two standard utilization categories:
AC-5a for discharge lamp switching.
AC-5b for incandescent lamp switching.

Slip-ring motor switching
The contactors used for short-circuiting rotor resistors can be used for rotor voltages up to 2 times the rated operational
voltage.
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The conditions of use of rotor contactors depend on the connection mode of the main poles. IEC 60947-4-1 stipulates
AC-2 utilization category for startor contactor.