Page 671 - V16 Catalogue Final

MOTOR PROTECTION

General
In a circuit that provides power to a motor a number of protective & Control devices are normally present. The combination of these devices must be coordinated to ensure
the efficiency & optimal protection of the motor. Here, the protection of such circuits strongly depends on the operational requirements, as the application for which the TECHNICAL
motor is used, the required starting frequency, required service level & applicable safety standards. RESOURCES

Ir setting
Category Load type (min)
AC1 Non Inductive motor Energization
AC2 Slip ring motor Starting
Switching off while running
Regenerative breaking
Inching
AC3 Squirrel-cage motor Energization
Switching off while running
AC4 Squirrel-cage motor Starting
(Cos phi = 0.45 <= 100A) Switching off while running
(Cos phi = 0.35 > 100A) Regenerative breaking
Pluging
Inching

Required
tripping time at
Trip Class 1.2 x In 1.5 x In 7.2 x In
10A t < 2 hours t < 2 min. 2 <= t <= 10sec.
10 t < 2 hours t < 4 min. 4 <= t <= 10sec.
20 t < 2 hours t < 8 min. 6 <= t <= 10sec.
30 t < 2 hours t < 12 min. 8 <= t <= 10sec.

COORDINATION TYPE 2 TEST SEQUENCE

Coordination
The standards require tests to define the coordination between the protective & switching devices within the motor circuit. Depending on the state of the components
after the test two coordination. Classes, 1 & 2 have been defined.

Motor current Test with
ie (AC3) current “r”
Ie <= 16A 1kA
16 < Ie <= 63A 3 kA
63 < Ie <= 125A 5 kA
125 < Ie <= 315A 10 kA
315 < Ie <= 630A 18 kA
After this test the original characteristics of the contactor and thermal relay
MUST remain unchanged. After this test the short-circuit protection must trip
within 10 ms at a fault current >= 15 x In.

Type 2 - Short-circuit test with current “Iq”
<= 50kA
This value which is generally 15kA is used to check the coordination of the de-
vice used in the motor starter circuit.
After test with this current the following conditions must be met.
No or minor welding of the contactors after testing; contact separation is
simple and easy.
The switchgear and controlgear are fully operational after test.

Phone: 1300 556 601 www.ipd.com.au V16-TR-R03 663