A soft starter is a novel motor control device that integrates soft starting, soft stopping, light-load energy saving, and multiple protection functions. It is known internationally as a Soft Starter. The soft starter uses three anti-parallel thyristors as voltage regulators, connected between the power supply and the motor stator. This circuit resembles a three-phase fully controlled bridge rectifier circuit. When starting the motor with a soft starter, the thyristor output voltage gradually increases, and the motor gradually accelerates until the thyristors are fully conducting. The motor then operates at its rated voltage mechanical characteristics, achieving smooth starting, reducing starting current, and preventing overcurrent tripping.
Once the motor reaches its rated speed, the starting process ends. The soft starter automatically replaces the thyristor with a bypass contactor, providing the rated voltage for normal motor operation. This reduces heat loss from the thyristor, extends the soft starter's lifespan, improves its efficiency, and prevents harmonic pollution from the power grid. The soft starter also provides a soft stop function. Soft stop is the reverse of the soft start process; the voltage gradually decreases, and the speed gradually drops to zero, avoiding torque surges caused by free stopping.
Wiring diagrams for five commonly used motor soft starters
I. The CMC-L series digital motor soft starter is a new type of motor starting and protection device that combines power electronics technology, microprocessor, and automatic control. It can smoothly start/stop the motor without step jumps, avoiding mechanical and electrical shocks caused by traditional starting methods such as direct starting, star/delta starting, and autotransformer reduced voltage starting. It can also effectively reduce starting current and power distribution capacity, avoiding investment in capacity expansion.
1. Basic wiring diagram of CMC-L series digital motor soft starter : Terminals 1L1, 3L2, and 5L3 of the soft starter are connected to the three-phase power supply, and terminals 2T1, 4T2, and 6T3 are connected to the motor. When a bypass contactor is used, it can be controlled by the built-in signal relay K2.
2. Basic wiring diagram of CMC-L series digital motor soft starter:
3. Typical application wiring diagram of CMC-L series digital motor soft starter:
Notice:
1. The diagram above shows a single-node control method. The soft starter starts when the contact is closed and stops when the contact opens. However, note that this wiring method does not enable LED panel start-up. Terminals 3, 4, and 5 form a passive node for start/stop signals.
2. The PE grounding wire should be as short as possible and connected to the grounding point closest to the soft starter. A suitable grounding point should be located on the mounting plate close to the soft starter. The mounting plate should also be grounded. This grounding is functional grounding, not protective grounding.
3. The secondary wire diameter of the current transformer shall not be less than 2.5 mm2.
II. The CMC-M series digital intelligent motor soft starter is a new type of motor starting and protection device that combines power electronics technology, microprocessor, and automatic control. It can smoothly start/stop the motor without step jumps, avoiding mechanical and electrical shocks caused by traditional starting methods such as direct starting, star/delta starting, and autotransformer reduced voltage starting. It can also effectively reduce starting current and power distribution capacity, avoiding investment in capacity expansion.
1. Basic Wiring Diagram: Terminals 1L1, 3L2, and 5L3 of the soft starter are connected to the three-phase power supply; terminals 2T1, 4T2, and 6T3 are connected to the motor. The soft starter can be configured to detect phase sequence via parameter settings. When a bypass contactor is used, it can be controlled by the built-in signal relay K2.
2. Basic Wiring Diagram
3. Typical application wiring diagram
Notice:
1. The diagram above shows a single-node control method. The soft starter starts when the contact is closed and stops when the contact opens. However, note that this wiring method does not enable LED panel start-up. Terminals 3, 4, and 5 form a passive node for start/stop signals.
2. The PE grounding wire should be as short as possible and connected to the grounding point closest to the soft starter. A suitable grounding point should be located on the mounting plate close to the soft starter. The mounting plate should also be grounded. This grounding is functional grounding, not protective grounding.
3. The secondary wire diameter of the current transformer should not be less than 2.5 mm². When wiring the current transformer, pay attention to the direction: P indicates the incoming line, and K indicates the outgoing line. Please wire according to the typical application wiring diagram.
III. The CMC-SX series intelligent motor soft starter with Chinese display is the only motor soft starter in China developed based on a 32-bit ARM core microcontroller. It is a new type of intelligent asynchronous motor starting and protection device. It is a motor terminal control device that integrates starting, display, protection, and data acquisition. Users can achieve complex control functions with fewer components. The Chinese and English interface display makes operation even simpler.
1. Basic Wiring Diagram: Soft starter terminals 1L1, 3L2, and 5L3 are connected to the three-phase power supply; soft starter terminals 2T1, 4T2, and 6T3 are connected to the motor. The soft starter can be configured to detect phase sequence via parameter settings. When a bypass contactor is used, it can be controlled by the built-in signal relay K2.
2. Basic Wiring Diagram
3. Typical application wiring diagram
Notice:
1. The diagram above shows a single-node control method. The soft starter starts when the contact is closed and stops when the contact is open. However, note that this wiring method does not enable LCD panel start-up. Terminals 3, 4, and 5 form a passive node for start/stop signals.
2. The PE grounding wire should be as short as possible and connected to the grounding point closest to the soft starter. A suitable grounding point should be located on the mounting plate close to the soft starter. The mounting plate should also be grounded. This grounding is functional grounding, not protective grounding.
3. The secondary wire diameter of the current transformer should not be less than 2.5 mm². When wiring the current transformer, pay attention to the direction: P indicates the incoming line, and K indicates the outgoing line. Please wire according to the basic wiring diagram.
IV. The CT series graded frequency converter soft starter is a new type of starting device with advanced international standards, manufactured using power electronics technology, microprocessor technology, and modern control theory. Through thyristor control, it achieves stepped frequency conversion, stepless voltage regulation, low starting current, and high starting torque. It integrates starting, display, protection, and data acquisition. Users can achieve complex control functions with fewer components. The bilingual (Chinese and English) interface further simplifies operation.
1. Basic Wiring Diagram: Soft starter terminals 1L1, 3L2, and 5L3 connect to the three-phase power supply; 2T1, 4T2, and 6T3 connect to the motor; B1, B2, and B3 connect to the bypass contactor. The soft starter can be configured to detect phase sequence via parameter settings. When using a bypass contactor, it can be controlled by the built-in signal relay K2.
2. Typical application wiring diagram
Notice:
1. The diagram above shows a single-node control method. The soft starter starts when the contact is closed and stops when the contact is open. However, note that this wiring method does not enable LCD panel start-up. Terminals X1\1, X1\2, and X1\3 form a passive node for start/stop signals.
2. The PE grounding wire should be as short as possible and connected to the grounding point closest to the soft starter. A suitable grounding point should be located on the mounting plate close to the soft starter. The mounting plate should also be grounded. This grounding is functional grounding, not protective grounding.
V. The CMC-MX series built-in bypass type motor soft starter is a new type of motor starting and protection device that combines power electronics technology, microprocessor, and automatic control. It can smoothly start/stop motors without abrupt changes, avoiding mechanical and electrical shocks caused by traditional starting methods such as direct starting, star/delta starting, and autotransformer reduced voltage starting. It also effectively reduces starting current and power distribution capacity, avoiding investment in capacity expansion. Furthermore, the CMC-MX soft starter integrates a current transformer and contactor internally, eliminating the need for external connections.
1. Basic Wiring Diagram: Terminals 1L1, 3L2, and 5L3 of the soft starter are connected to the three-phase power supply, and terminals 2T1, 4T2, and 6T3 are connected to the motor. No external bypass contactor is required; the soft starter can be configured to detect phase sequence via parameter settings.
2. Diagram of inscribed triangle
If the user uses a delta connection, the connection must be strictly made according to the diagram below; otherwise, damage to the motor or soft starter may occur. The machine will check the motor wiring before startup; if the wiring is incorrect, the soft starter will report a wiring error fault.
3. Typical application wiring diagram
Notice:
1. The diagram above shows a single-node control method. The soft starter starts when the contact is closed and stops when the contact opens. However, note that this wiring method does not enable LED panel start-up. Terminals 3, 4, and 5 form a passive node for start/stop signals.
2. The PE grounding wire should be as short as possible and connected to the grounding point closest to the soft starter. A suitable grounding point should be located on the mounting plate close to the soft starter. The mounting plate should also be grounded. This grounding is functional grounding, not protective grounding.
