What Are the Applications of Thermal Overload Relay?

Thermal overload relay, as a kind of electrical device which can realize protection by monitoring the thermal effect of current, plays a key role in industrial and civil electrical systems. Base on that thermal deformation principle of the bimetallic strip, the circuit can be cut off in time when the equipment is overloaded, and the damage of equipment such as a motor, a transform and the like caused by long-time overheating can be effectively prevented.

Core Operating Principles

Thermal memory effect and precision protection thermal overload relay adopts bimetal thermal bending technology, and its operating characteristics are highly matched with thermal characteristics equipment.

Heat accumulation simulation: the rate of bimetallic strip bending under heating is synchronous with the heating process of equipment, which truly reflects the temperature rise of equipment

Inverse-time protection: the greater the overload current, the shorter the action time; short-time operation is allowed for small-amplitude overload to avoid maloperation

Phase balance monitoring: some advanced models have the function of open-phase protection, which acts in advance when the three-phase current is unbalanced

Main application fields

1. Industrial power equipment of motor protection system: continuous operation equipment such as fan, water pump, compressor, conveyor belt, etc.

Periodic load equipment: frequent start-stop scenarios of injection molding machine, stamping machine, elevator, etc.

Setting of key protection parameters: the setting current is usually set to 1.05-1.2 times of the rated current of the motor

2. Distribution and Transformer Protection Dry-Type Transformer Cooling Fan Control

Overheat protection of capacitance compensation device

Low-voltage distribution branch backup protection

3. Special environmental applications High ambient temperature locations: Ambient temperature compensated relays are required

Frequent vibration scenarios: Industrial grade products requiring anti-vibration and ruggedized design

Areas with explosion-proof requirements, complete protection scheme shall be formed with explosion-proof enclosure.

FAQ

Q1: Can thermal relay be used instead of fuse?

I can't.  Thermal relay is designed for overload protection with long action time; short-circuit protection shall be combined with circuit breaker or fuse to realize double protection.

Q2: Is a thermal relay required for the inverter drive motor?

Yes, it is.  Although the drive has an electronic protection function, external thermal relays provide independent redundant protection and comply with safety regulations.

Q3: Does the SPX relay support special environment customization?

Yes, sir.  We offer special coating, sealing and material solutions for high temperature, high humidity and corrosive environments.