Basic Selection Methods for Motor Protectors - Motor Intelligent Protectors

Currently, there is no unified standard for motor protectors on the market; almost every manufacturer has its own model specifications. Manufacturers aim to meet the diverse needs of different customers.

A wide variety of different products with numerous applications have been derived from the demand, which can be quite cumbersome for users to select from. When choosing, users should give full consideration to

Motor protection actual requirements, selecting reasonable protection functions and methods, can achieve good protection effectiveness, and improve the reliability of equipment operation.

To enhance safety, reduce unplanned stops, and minimize accident-related losses.

I. Conditions Related to Selection: The selection of motor protection involves the rational matching relationship between the motor and the protector. The following provides several:

Conditions and factors related to protection, for reference in user selection.

1. Motor aspects: first understand the model specifications, motor performance characteristics, protection type, rated voltage, rated current, rated power, electrical

Source frequency, insulation grade, etc. (These details essentially provide users with a reference for correctly selecting and using motor protectors.)

2. Environmental Conditions: Primarily refers to normal temperature, high temperature, extreme cold, corrosion level, vibration, sandstorms, altitude, electromagnetic pollution, etc.

3. Motor Applications: Such as fans, pumps, air compressors, lathes, oil field sucker rods, etc., with different mechanical characteristics for various loads, such as pump motor protectors.

The device should have a fire loading function, and the protector needs to issue a protection command when the pump has exhausted the water.

4. Control Systems: featuring manual, automatic, on-site control, remote control, standalone operation, centralized production line control, and more.

Start-up methods include direct, reduced voltage, delta-wye, frequency-sensitive resistor, variable frequency drive, and soft start, etc.

5. Other aspects: How lenient or strict users are in overseeing on-site production management, the severity of the impact of abnormal shutdowns on production, etc.

Note: Many factors are related to the selection of motor protectors, such as the installation location, power supply conditions, and compatibility with the distribution system; also

Consider whether it is for a new motor protector, an upgrade for the motor protection, or an enhancement of the accident motor protection; also, consider the motor

The difficulty of changing protection methods and the extent of their impact on production; the selection and adjustment of motor protectors should be considered comprehensively based on the actual working conditions on-site.

Section 2: Common Types of Motor Protectors

1. Thermal Relay: Standard small capacity AC motor, under good working conditions, no frequent startups or harsh conditions; due to poor accuracy, lacks missing...

Protective function, reliability cannot be guaranteed; not recommended for use.

2. Motor protector: Detects the current and voltage values of a single phase, the set current value is adjusted using a push-button digital operation, and the circuit usually employs integrated circuits.

(Microcontroller), featuring inverse-time operating characteristics. Protection functions include overload, phase loss, three-phase imbalance, stall, overvoltage, undervoltage, leakage, etc.

Fault protection: Fault types are indicated by a LED indicator and displayed on a liquid crystal screen (digital tube), such as the GY100 series being an example of such a motor protector.

3. Comprehensive Intelligent Type: Detects three-phase current values, employs a microcontroller for motor protector, realizing intelligent comprehensive protection for motors, integrating protection, measurement,

The unit displays as a single entity, with the set current utilizing digital adjustment. Operation is via the control panel buttons, allowing users to configure according to their actual usage requirements and protection needs.

The on-site conditions automatically adjust and set various parameters, utilizing a digital tube as the display window, or a large-screen LCD with full Chinese and English characters display.

The price is relatively higher, suitable for more important applications, and currently, intelligent protection is universally adopted for low-voltage electric motors.

4. Thermal Protection Type: A thermal element is embedded in the motor for temperature-based protection. The protection is general and exhibits temperature hysteresis.

When the motor capacity is large, it should be used in conjunction with a current monitoring type to prevent a rapid temperature rise when the motor stalls, due to the lag of the temperature sensing element.

Sex, leading to damage of the motor winding.

5. Magnetic Field and Temperature Detection Type: Immerse magnetic field detection coils and temperature probes within the motor, detecting changes in the internal rotating magnetic field and temperature of the motor.

Protect against changes, main functions include overload, stall, phase loss, overheat protection, and wear monitoring, with comprehensive protection features; the drawback is that it requires electrical

Magnetic field detection coils and temperature sensors are installed internally, making it difficult to use in complex field environments. Currently, it is only suitable for laboratory use.

III. Selection of Motor Protectors under Motor Operating Conditions

1. Standalone units with low requirements for working conditions, simple operation and control, relaxed monitoring and management, and minimal impact on production from downtime.

Motivation: The standard type protector can be selected due to its simple structure, ease of installation, wiring, replacement, and operation on-site. It has been widely used.

High cost-performance features.

2. For high requirements in working conditions, where both safety and continuity are critical, and with a high degree of automation, specialized personnel are needed for control, supervision, and management.

In a MCC system requiring network monitoring, a medium-range motor protector with comprehensive functions should be selected.

3. For explosion-proof motors, due to bearing wear causing eccentricity, it may lead to high temperature friction at the explosion-proof gap, posing an explosion hazard. It is recommended to:

Wear status monitoring feature. For high-capacity high-pressure submersible pumps, due to the difficulty in inspection and maintenance, the wear status monitoring feature should also be selected to avoid occurrences

A sweep accident has caused significant economic losses.

4. Motor protection cases for explosion-proof environments should be selected based on the specific requirements of the application site, to avoid installation errors.

All incidents have occurred.