Mike Dolt Enterprises
Mike Dolt Enterprises
User: electrofelon, Location: Cherry Valley NY, Seattle, WA
Asked on: Tuesday, June 1, 2021 at 12:37 pm EDT
Answered on: Thursday, June 20, 2024 at 11:27 am EDT
Question: I got into a discussion about what exactly happens when a generator is overloaded. Say your typical generac standby generator for example. Considering the breaker on the generator is usually next size up from the rated current, and the trip time curve of the breaker, I am not sure the breaker would ever trip. Do generators typically have protection built-in that will shut them down on overloads? If so is this based on current or frequency?
Generator Overload Protection
Generators typically have built-in overload protection mechanisms to prevent damage in the event of excessive load. These mechanisms may include
1. Circuit Breaker:
Most generators have a circuit breaker connected to the output terminals. When the current draw exceeds the rated capacity of the generator for a prolonged period, the circuit breaker will trip, disconnecting the load from the generator.2. Thermal Overload Protector
Generators may also have a thermal overload protector that monitors the temperature of the windings. If the temperature rises too high, the protector will activate, shutting down the generator.
3. Frequency Monitoring
Some generators use frequency monitoring to detect overloads. When the load draws excessive current, the generator voltage drops, resulting in a decrease in frequency. The generator may be equipped with a low-frequency cutoff that triggers when the frequency drops below a certain point, shutting down the generator.
Trip Time Curve of Circuit Breaker
The trip time curve of a circuit breaker determines the amount of time it takes the breaker to trip at different current levels. Typically, generators use a type of circuit breaker known as an "inverse time" breaker. This means that the trip time increases as the current increases. This allows the generator to handle temporary overloads without tripping.
Generator Overload Protection Considerations Breaker Size
The breaker on a generator is typically sized slightly larger than the rated current of the generator to allow for temporary overloads.
Trip Time Curve
The inverse time curve of the breaker helps prevent nuisance tripping during transient loads.
Built-In Protection
Generators are typically equipped with one or more overload protection mechanisms to protect themselves and the load.
Load Type
The type of load connected to the generator can affect the generator's behavior under overload conditions. Reactive loads, such as motors, can cause larger current draws than resistive loads.
Overload Symptoms
When a generator is overloaded, it may exhibit the following symptoms: Voltage drop Frequency decrease Overheating Circuit breaker tripping Thermal overload protector activation* Shutting down of the generator Flag for review