Technical Specifications

FAQ

1. What is the main function of the Schneider Electric ATS48C21Q soft starter?

The ATS48C21Q is a high-power Altistart 48 soft starter designed to control the starting and stopping of three-phase asynchronous motors. It uses torque-controlled starting to progressively control motor acceleration instead of applying full supply voltage directly to the motor. This helps reduce electrical stress caused by high starting current and minimizes mechanical shock throughout the drive system. The ATS48C21Q is well suited to large pumps, fans, compressors, conveyors, and high-inertia industrial machinery. Integrated motor thermal protection, starter protection, and phase-loss detection provide additional protection during starting and normal operation.

2. What motor power range is suitable for the ATS48C21Q?

The applicable motor power depends on the supply voltage, motor connection method, and whether the application is standard duty or heavy duty. The ATS48C21Q has a rated current of approximately 210 A for line connection and up to approximately 364 A for delta connection. At 400 V, a line-connected motor can typically be rated around 110 kW for standard-duty applications and around 90 kW for heavy-duty applications. With delta connection, the applicable rating can reach approximately 160 kW for standard duty and 132 kW for heavy duty. Actual selection should be based primarily on motor rated current, starting time, load inertia, starting frequency, and operating duty rather than motor power alone.

3. What supply voltage and frequency does the ATS48C21Q support?

The ATS48C21Q is designed for three-phase AC supplies from 230 to 415 VAC, with a supply voltage tolerance of approximately -15% to +10%. Its normal operating frequency is 50–60 Hz, with an allowable frequency range of approximately 47.5–63 Hz. Before commissioning, the actual three-phase supply should be measured and compared with the soft starter and motor nameplate requirements. The motor connection must also match the selected supply voltage. Incorrect voltage, phase configuration, or motor connection can result in insufficient starting torque, excessive current, overheating, or protective trips.

4. How does torque control improve motor starting with the ATS48C21Q?

The ATS48C21Q uses torque control to manage the motor’s acceleration from standstill to normal operating speed while limiting starting current. Compared with direct-on-line starting, this approach reduces both electrical and mechanical stress during acceleration. For pump systems, smoother starting can reduce sudden hydraulic and mechanical shock. For conveyors, it can reduce stress on belts and transmission components. For high-inertia machinery, controlled torque helps provide a more stable acceleration process. The starting parameters should be adjusted according to the actual motor and load characteristics so that sufficient torque is available without unnecessarily extending the acceleration period.

5. What should be checked if the motor does not accelerate properly with an ATS48C21Q?

First, verify that all three input phases are present and that the supply voltage is within the permitted range. Then check the motor rated-current setting, motor wiring, connection method, main power circuit, and control inputs. If a delta connection is used, the motor terminals and soft starter connections should be carefully verified. If the electrical system is correct, inspect the mechanical load for blocked pumps, seized bearings, conveyor obstruction, excessive friction, or excessive load inertia. The current limitation should also be reviewed. If it is set too low, the motor may not generate enough torque to accelerate the load. An unusually long acceleration time can indicate either insufficient starting torque or a mechanical load problem.

6. Why might the ATS48C21Q trip during motor starting?

A starting trip can be caused by phase loss, abnormal supply voltage, motor overload, incorrect motor parameters, excessive acceleration time, excessive mechanical load, or unsuitable current-limiting settings. When a fault occurs, the diagnostic information should be checked first to identify the actual fault condition. The three-phase supply, motor wiring, and motor nameplate data should then be verified. For high-inertia machinery, the required acceleration time and thermal loading should also be evaluated. Mechanical problems such as a blocked pump, jammed transmission, or damaged bearing can cause the motor to draw excessive current even when the electrical installation is correct. Increasing protection limits without identifying the underlying cause should be avoided because it may result in excessive motor or starter heating.

7. How should motor thermal protection be configured on the ATS48C21Q?

The motor rated-current parameter should be configured according to the actual value stated on the motor nameplate and should correspond to the motor’s connection method. The ATS48C21Q uses this information as an important reference for its integrated motor thermal protection. If the configured current is too high, an actual overload may not be detected quickly enough. If it is too low, nuisance trips may occur during normal starting or operation. For large motors, ambient temperature, motor cooling, load percentage, starting frequency, and continuous operating time should also be considered. Heavy-duty and frequently started applications require particular attention to thermal accumulation over the complete operating cycle.

8. What should be checked before installing or replacing an ATS48C21Q?

Before installing or replacing an ATS48C21Q, verify the motor rated voltage, rated current, power, frequency, connection method, and mechanical load characteristics. The correct soft starter capacity should be selected according to the actual standard-duty or heavy-duty application. The three-phase supply, main power circuit, control circuit, grounding system, and protective devices should all be inspected before energization. Because the ATS48C21Q uses forced-air cooling, adequate ventilation around the unit should be maintained to prevent reduced cooling performance. After wiring, check the motor rated-current setting, starting parameters, current limitation, control inputs, and protection functions. During commissioning, perform controlled start tests while monitoring motor current, acceleration time, fault conditions, and operating temperature. For high-inertia, heavy-duty, or frequently started equipment, the complete starting cycle and thermal load should be evaluated to ensure reliable long-term operation.