How smart motor controls can maximize resilience and uptime
value in another phase is greater than 0.8 Ir, the overload relay triggers within 4 ±1 seconds. Phase loss protection cannot be disabled and must be reset manually.
Phase imbalances
Phase imbalances cause overheating of an asynchronous motor. Common causes include:
■ Long main supply line
■ Defective contact on the incomer switch
Figure 3: The front panel of TeSys Giga overload relays includes status LEDs and protection adjustments. (Image source: DigiKey)
■ Imbalanced network
When the imbalance ratio exceeds 40%, the overload relay triggers in 5 ±1 seconds. Phase imbalance protection must be reset manually.
for use with AC motors. Settings for ground fault protection, phase imbalance protection, and trip class (5, 10, 20, and 30) are configurable on the front panel. The front panel also includes alarm and status LEDs. They have wide adjustable thermal overload protection ranges that enable four overlapping models to handle applications from 28 A to 630 A (Figure 3): ■ LR9G115, adjustable from 28 to 115 A ■ LR9G225, adjustable from 57 to 225 A ■ LR9G500, adjustable from 125 to 500 A ■ LR9G630, adjustable from 160 to 630 A
Thermal overloads
Thermal overload protection is used with single-phase and three-phase asynchronous motors. The current level for thermal overload protection can be adjusted based on the model of the overload relay being employed. In addition, the trip class and associated delay are adjustable. Thermal overload protection can be set for automatic or manual resetting.
Ground faults
Ground-fault protection is used to protect three-phase asynchronous motors. A ground fault occurs when the insulation on the load circuit becomes ineffective due to vibration, moisture, or other factors. The overload relay monitors the ground current (Ig). When the Ig exceeds more than 10% of Ir, the relay trips in 1 ±0.2 seconds. Ground fault protection must be reset manually.
Phase loss
Phase loss protection is used to protect three-phase asynchronous motors from overheating. The overload relay continuously monitors the current in each phase. When the current value in one of the phases is lower than 0.1 of the rated current (Ir), and the current
Modularity
The modular design of TeSys Giga contactors can be especially useful if excessive contact wear
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