Why Does the Main Supply Trip When Turning on the Inverter?

The issue of a main supply tripping while turning on an inverter can often be perplexing. This article aims to help clarify the possible reasons behind this occurrence and provide guidance on how to address it.

Understanding the Role of Transformers

While a transformer may seem to play a role in such tripping incidents, it's important to recognize that a transformer, especially an isolation transformer, can indeed cause significant issues. A transformer is designed to reduce or step-up the voltage, and it can draw a large amount of current during startup. This is known as surge current and can be substantial enough to trip upstream breakers or circuit protection devices.

Is the Inverter Too Large for the Circuit?

One common reason for the main supply to trip is that the inverter is too large for the circuit it is connected to. It's crucial to check the power specifications of both the inverter and the circuit breaker to ensure they match. Inverter manuals typically provide detailed guidelines on recommended circuit breaker sizes. Ignoring these guidelines can lead to tripping and potential damage to the inverter.

Surge Currents and Inadequate Supply Circuit

In addition to the inverter size, surge currents can also be a significant factor in tripping the main supply. When an inverter is turned on, it may draw a peak current that is much higher than the steady-state operating current. This initial surge can overwhelm the circuit and cause the breaker to trip. The surge current is a temporary spike in current that occurs during the startup phase of devices like inverters.

To mitigate this issue, consider using a circuit that can withstand the initial surge current. This may involve increasing the size of the circuit breaker or using a dedicated circuit with a higher capacity. In some cases, using a surge protector or a surge protection device can also help prevent the breaker from tripping.

Consulting an Electrical Engineer

For more complex scenarios, it might be necessary to consult an experienced electrical engineer. They can perform a detailed coordination study to ensure that all circuit elements are properly sized and coordinated. An experienced electrical engineer can provide valuable insights and recommendations to prevent tripping issues.

Here are a few key points to consider when consulting an electrical engineer:

Size of the Inverter: Ensure that the inverter is not excessively oversized for the circuit. Surge Currents: Understand the surge current requirements and ensure the circuit can handle it. Circuit Protection: Properly size circuit breakers and other protective devices to prevent unnecessary tripping. Coordinated System: Ensure that all components are properly coordinated to work together without causing issues.

Conclusion

Tripping of the main supply when turning on an inverter can be caused by several factors, including surge currents, an inadequate circuit, and improperly sized components. Addressing these issues through proper electrical design, using appropriate equipment, and consulting with an electrical engineer can help prevent such problems in the future.

Remember, the safety and reliability of electrical systems are paramount. Proper understanding and adherence to standards and guidelines can significantly reduce the likelihood of such occurrences.