Summary of "Relais Thermique : Réglage, Montage, Raccordement (partie 2)"

Thermal Protection Relays Tutorial (Part 2)

This video tutorial provides a detailed guide on thermal protection relays, focusing on their adjustment, mounting, and wiring connections. It is aimed at electricians and technicians involved in installing or maintaining these devices.

Adjustment of Thermal Relays

The relay features a small rotating dial on the front, adjustable using a Phillips screwdriver.
Adjustment ranges are manufacturer-limited (e.g., 2.5 to 4 amps).
The dial should be set to the motor’s nominal current (for example, 3 amps).
A test button/window allows manual triggering of relay contacts to verify wiring and operation.

Relay Contacts and Testing

During testing:
- Contacts 95 and 96 open.
- Contacts 97 and 98 close.
This behavior helps confirm correct wiring and proper relay operation.
The STOP button opens contacts 95 and 96 without closing 97 and 98, which is useful for wiring checks.

Sealing Option

The relay can be sealed to prevent unauthorized adjustments.
Seals are applied on the cover to secure the settings.

Mounting Options

Independent Mounting: Requires a compatible base (e.g., Schneider Electric LAD7 B106) that clips onto a DIN rail and connects to terminals 1, 3, and 5.
Direct Mounting: The relay can be mounted directly onto a motor contactor via three copper tabs. This method saves wiring effort and space inside control cabinets.

Connection and Application

The relay shown is a three-phase, three-pole model designed for three-phase synchronous motors.
It can also be used in single-phase setups by passing current through each phase.
Thermal relays are differential devices that monitor current balance across phases to detect imbalances and prevent nuisance tripping.

Temperature Compensation

The relay includes a compensation bimetallic strip.
This feature maintains consistent tripping behavior regardless of ambient temperature variations (e.g., from 0°C to 40°C).

Tripping Characteristics and Selection

Example: The Schneider LR9F relay trips after about 4 seconds if a phase is missing or if there is a phase imbalance of 30% or more.
Relay classes affect trip time:
- Class 10: 4–10 seconds
- Class A: 2–10 seconds
Selecting the correct relay depends on:
- The motor’s rated current (from the motor nameplate).
- Ensuring the relay’s adjustment range includes this nominal current.

Practical Advice

Always check the motor nameplate data before selecting and adjusting the relay.
The video demonstrates how to wire the relay in typical motor control circuits.

Note: The tutorial is presented by an individual hosting a technical channel focused on electrical components and installations, offering concise micro-capsules on specific devices like thermal protection relays.