Operating Conditions of Electric Machines
For the longevity and reliability of electric machines, it is important to adhere to certain conditions, which are traditionally referred to as proper operating conditions. All warranty obligations contain stipulations stating that the ideal operation of the device is only possible if these conditions are met. During the operation of electric motors, protective and starting-regulating equipment should be used, as the load level and its duration directly affect the service life of the electric motor.
Protection of Electric Motors from Overheating
To prevent overheating, which may occur due to current overloads, thermal relays are used. These devices, utilizing various sensors, provide temperature regulation, control of technological processes, and protection of the electric motor. The most commonly used types of thermal relays include:
Problems Solved by Thermal Relays
We strive to ensure that any equipment lasts a long time, especially for expensive devices. Thermal relays play an important role for electric motors. Let’s consider the main issues that relays help to address:
- If the rated voltage is continuously exceeded, the equipment heats up, which may lead to premature failure;
- High temperatures reduce the service life of insulating windings and materials, leading to the degradation of the electric motor's insulation;
How a Thermal Relay Provides Protection
The principle of operation of the relay is simple: it is based on the thermal effect of current between flat surfaces that have different coefficients of linear expansion. When the temperature changes, one plate bends; upon heating to a certain temperature value, it presses on the tripping mechanism, disconnecting the electric circuit and stopping the operation of the electric motor.
Main Situations for Thermal Relay Activation
- The relay activation may indicate the presence of a malfunction that is difficult to detect. The identification of such faults can be done even during a brief inspection;
- The relay can also activate under normal operating conditions if there is poor contact, leading to heating at the connection point;
If the thermal relay has activated, restarting the electric motor is only possible after the thermal element has cooled down. The electric motor requires more time to cool down than the relay. If the motor is not designed for frequent restarting, such actions are not recommended.
How to Properly Choose a Thermal Relay
For the correct selection of a relay, it is necessary to consider the current value consumed by the electric motor. It is advisable to choose a relay that is 1.5 times greater than the rated current. The ambient temperature should also be taken into account, as often at low air temperatures, the current disconnection value of the relay is set below the rated level.
The modern market offers a wide variety of different types of relays. To ensure your choice is correct, it is best to consult a specialist who can provide qualified advice. The staff of our company can assist not only in selection but also in the installation and configuration of the device. Feel free to contact us via email: info@chastotnik.ua. We are always happy to help!