How to Choose The Suitable Generator Automatic Transfer Switch?

Decisive factor

The selection of automatic switching switches for diesel generators requires consideration of many factors, especially size. Let's first discuss the load type, rated voltage, and continuous current.

Careful selection of automatic transfer switches ensures the highest reliability and sufficient capability in both normal and emergency situations. However, the most common influencing factors ultimately are price and reliability.

Various different loads

Classification of automatic switching loads in the industry. The listed loads include the total system load, motor load, discharge lamp load, limit load, and incandescent lamp load. In addition, it is required that all transfer switches of diesel generators clearly indicate the type of load they can handle. The "Total System Load" panel indicates that the switch can be used for various loads as described in the previous paragraph. However, if the conversion switch is used to transmit a larger proportion of power to the incandescent lamp, the total load should not exceed 30% (tungsten based lamp).

In general, most of the conversion switches used in old generators can handle the total system load. A better method is to check the markings, as some overall system loads are marked as "resistance only, tungsten only, etc.". At the beginning of the project, by selecting the overall system load, engineers can greatly reduce the hassle of overall project management.

Rated voltage value

In the distribution system, the automatic transfer switch of the second-hand generator is the only one, as it is one of the few appliances used to connect two asynchronous power sources. For example, in a 480 volt AC system, the voltage applied to the insulation side of the equipment may reach 960 volts. The carefully designed UL conversion switch will provide sufficient spacing and insulation to cope with increased voltage stress.

The spacing of this type of transfer switch should be less than the spacing shown in UL1008 Table 22.1, regardless of whether it is used as a component of the transfer switch for this reason.

The rated voltage of an AC system is generally 120208240480600 volts, single-phase or multiphase. The standard frequency is 50 or 60Hz. Automatic transfer switches can be used for other voltages and frequencies as needed, including DC.

Components of other continuous rated current automatic transfer switches.

The standard expectation for automatic transfer switches with continuous loads is that the switch should be able to maintain its maximum value for three hours or longer. The difference between converters and other emergency devices is that they must continuously deliver current to the main load, whether from a normal power source or an emergency power source. Backup generators usually only provide electricity in emergency situations.

The manufacturing of automatic transfer switches for diesel generators meets the rated continuous current of 30-4000 amperes. Generally speaking, the most commonly used ampere ratings are 30, 40, 70, 80100, 150, 225, 260, 400, 800, 1000, 1200, 1600, 2000, 3000, and 4000 amperes.

A new type of conversion switch technology that can achieve 100% current output at an ambient temperature of 40 ° C. The transfer switch with integrated overcurrent protection device can be limited to a continuous load current of no more than 80% of the rated value of the switch. For modern switches, there should be appropriate control to ensure that no more than 80% of the load is continuous. However, in old equipment, the likelihood of system failure exceeds 80%.

In the planning process, project engineers should predict future load demands. Not all projects need to consider future load demands in advance, but it is usually recommended to choose a transfer switch with a rated continuous current equal to the total load.

To calculate the continuous rated value of the transfer switch, it is necessary to calculate the current required for all loads; To determine the load current of tungsten (incandescent lamp) and electric heater, it is necessary to calculate the total power. The load current of mercury vapor, fluorescent lamp vapor, and sodium vapor lamps ensures that it is the current of the ballast or autotransformer, rather than the total power of the lamp.

The full load current of the motor only determines the motor load and cannot accurately measure other types of loads. When determining the size of the transfer switch for the total system load listed in UL, there is no need to consider the inflow current of the locked rotor and motor. In most cases, when used in an ambient temperature of 40 ° C, it is not necessary to lower the rated value of the transfer switch; This includes switches installed in distribution boards or independent boxes.

Dingbo Power was founded in 1974 and is one of the earliest manufacturers of generators and diesel generator sets in China. If you want get more information, please feel free to send email to sales@dieselgeneratortech.com we will pay highly attention on your question.