Even when the ATS48 soft starter is in the OFF state and the motor is disconnected, a residual voltage may still be observed at the output terminals. This is normal behavior and occurs due to the internal design of the starter.
⚙️ Technical Explanation:
- Inside the ATS48, thyristors are used to control power to the motor.
- In parallel with each thyristor, an RC snubber circuit (a resistor and capacitor combination) is installed.
- These RC circuits are used to assist with thyristor commutation and to protect against voltage spikes.
⚡ Why Residual Voltage Appears:
- Even when the thyristors are not conducting (i.e., not triggered), the RC snubber circuits allow a small leakage current to pass through.
- This results in a residual voltage being present at the output terminals.
- This voltage is not capable of driving a motor but can be measured with a voltmeter or seen on sensitive equipment.
📌 Important Note:
- This residual voltage is not a fault and does not indicate a malfunction.
- However, it’s good practice to isolate the starter completely before performing any maintenance or testing.
Released for: Schneider Electric India
