MC91 HESG440588R4 HESG112714/B protection power module

The provided text describes two motor protection functions: “MC91 HESG440588R4 HESG112714/B Run-up protection Istart (mode 13)” and “Thermal overload protection (modes 30 to 39).” Here’s a summary of each:

MC91 HESG440588R4 HESG112714/B Run-up protection Istart (mode 13):

• Purpose: Protects induction motors during the run-up phase.
• Principle: Utilizes the integral I²T derived from phase-to-neutral current to measure thermal stress on the motor.
• Operating Principle:
  1. When input current falls below 0.1 x IE, the relay expects a motor start, inhibiting overcurrent and no-load functions.
  2. A timer starts when input current exceeds 0.1 x IE:
     • If the input current rises above the setting of Istart within 100 ms, a motor start is assumed, and I²T function is enabled.
     • The starting sequence continues until the current falls below Istart, reactivating overcurrent and no-load functions.
     • If Istart is not reached within 100 ms, it’s not considered a normal start, and overcurrent and no-load functions are reactivated.
  3. After Istart function resets, the relay waits 500 ms before considering a starting sequence complete to account for voltage dips.

Thermal overload protection (modes 30 to 39):

• Purpose: Protects motor from thermal overload during steady-state operation.
• Principle: Temperature rise in steady-state operation follows an exponential function.
• Operating Principle:
  1. Temperature rise ∆ϑ in steady-state operation is calculated using an exponential function based on time constants.
  2. Time constants are determined based on phase-to-neutral currents:
     • τ↑ for currents 0.1 x IE ≤ I < 2 x IE
     • τ↓ for currents I < 0.1 x IE
     • τ↑ → ∞ (adiabatic temperature rise) for currents I ≥ 2 x IE
  3. Steady-state temperature at a given current is calculated based on the maximum of three phase-to-neutral currents.
  4. Temperature rise and cooling curves can be calculated using the provided equations and figures.

These protection functions ensure safe operation of induction motors by monitoring current and temperature to prevent damage during start-up and steady-state operation.