How to use a multimeter to judge whether a soft starter is good or bad

A multimeter is a common measuring tool used by electricians. It can be used to measure parameters such as voltage, current, and resistance. A soft starter is a device used to start a motor. It can reduce the current shock when the motor starts and extend the service life of the motor. This article will detail how to use a multimeter to judge the quality of a soft starter.

1. Basic knowledge of multimeter

1. Types of Multimeters

Multimeters are mainly divided into two types: digital multimeters and analog multimeters. Digital multimeters have the advantages of high measurement accuracy and convenient reading, while analog multimeters have the advantages of low price and easy operation. When judging the quality of a soft starter, it is recommended to use a digital multimeter.

1. Measurement functions of a multimeter

The multimeter has a variety of measurement functions, including voltage measurement, current measurement, resistance measurement, etc. When judging the quality of the soft starter, the resistance measurement function is mainly used.

1. How to use a multimeter

When using a multimeter, you need to select the appropriate measurement function and range according to the object being measured. When measuring resistance, you need to connect the red probe of the multimeter to one end of the resistor being measured and the black probe to the other end. Then observe the reading of the multimeter to get the resistance value of the resistor being measured.

2. Basic knowledge of soft starter

1. Working principle of soft starter

The soft starter achieves smooth starting of the motor by controlling the voltage and current when the motor starts. During the starting process, the soft starter gradually increases the voltage of the motor to keep the starting current of the motor at a low level, thereby reducing the current shock when the motor starts.

1. Soft starter components

The soft starter is mainly composed of three parts: control unit, power unit and protection unit. The control unit is responsible for receiving the start signal and controlling the working state of the soft starter; the power unit is responsible for controlling the voltage and current of the motor; the protection unit is responsible for monitoring the working state of the motor and protecting the motor from abnormal conditions.

1. Common faults of soft starters

Common faults of soft starters include control unit failure, power unit failure and protection unit failure. Control unit failure may cause the soft starter to fail to start or stop normally; power unit failure may cause the motor starting current to be too large or fail to start; protection unit failure may cause the motor to fail to be effectively protected under abnormal conditions.

3. Use a multimeter to judge the quality of the soft starter

1. Check the appearance of the soft starter

Before judging the quality of a soft starter, first check the appearance of the soft starter to see if there is obvious damage, burning or deformation. If the appearance of the soft starter is obviously damaged, then the soft starter is likely to be damaged.

1. Measuring the resistance of a soft starter

Use the resistance measurement function of a multimeter to measure the resistance value inside the soft starter. Here are some common measurement methods:

(1) Measure the resistance of the control unit

Set the multimeter to the resistance measurement range, connect the red test lead to the input terminal of the control unit, and the black test lead to the output terminal. If the reading is infinite or close to infinite, it means that the resistor inside the control unit is damaged.

(2) Measure the resistance of the power unit

Set the multimeter to the resistance measurement range, connect the red probe to the input terminal of the power unit, and the black probe to the output terminal. If the reading is infinite or close to infinite, it means that the resistor inside the power unit is damaged.

(3) Measure the resistance of the protection unit

Set the multimeter to the resistance measurement range, connect the red test lead to the input terminal of the protection unit, and the black test lead to the output terminal. If the reading is infinite or close to infinite, it means that the resistor inside the protection unit has been damaged.

1. Check the soft starter wiring

Check whether the wiring of the soft starter is correct, including the control line, power line and motor line. If the wiring is wrong, the soft starter may not work properly.

1. Check the soft starter parameter settings

Check whether the soft starter parameter settings are correct, including starting time, starting current, etc. If the parameters are set incorrectly, the soft starter may not start normally or the starting current may be too large.

1. Check the grounding of the soft starter

Check the grounding of the soft starter and ensure that it is well grounded. If the grounding is poor, the soft starter may not work properly or there may be safety hazards.

1. Check the heat dissipation of the soft starter

Check the heat dissipation of the soft starter to ensure that the heat dissipation is good. If the heat dissipation is poor, it may cause the soft starter to overheat and affect its normal operation.

1. Check the protection function of the soft starter

Check whether the protection function of the soft starter is normal, including overload protection, short circuit protection, etc. If the protection function fails, the motor may not be effectively protected under abnormal conditions.

1. Check the soft starter's starting effect

After ensuring that the appearance, wiring, parameter settings, grounding, heat dissipation and protection functions of the soft starter are normal, you can conduct an actual start test. Observe the starting process of the motor to see if it is smooth and impact-free. If there is an abnormality during the starting process, it means that there may be a problem with the soft starter.