Solutions > Frequently-used Power Supply
Frequently-used Power Supply
Genset required to work continuously for a long time as frequently-used power supply of power load is called frequently-used genset. Generally, the capacity of frequently-used genset is relatively higher. It can run both in parallel or independently and does not run in parallel with the regional power grid; besides, it is not subject to power grid failures and has higher reliability. So it has been widely used in engineering. The following needs to be ensured for frequently-used power supply:
I. Capacity of frequently-used genset
The genset capacity eventually required by user is calculated on the basis that the output power of long-running genset can meet the calculated maximum load of the whole project. The type of load is usually one of the major considerations in selecting the genset capacity. Load is generally divided into: linear load (e.g., resistive load or inductive load) and non-linear load including rectifier circuit (also known as rectifier load).
The resistive load features nearly unchanged resistance, while current decreases with voltage proportionally. With this type of load, the genset is only required to have a capacity slightly higher than the load.
For inductive load (e.g., 3-phase squirrel-cage asynchronous motor), there is large current during startup, and the power factor is much less than its normal operating value. If it is started up directly, the starting current is 5-7 times that of normal operating, which means that the genset shall have enough capacity to meet the startup requirements. But as a frequently-used genset, it may turn out to be of too much power, since the normal operation power is much less than the genset’s rated power, which is obviously wasteful. If the capacity of the genset is too low, it would be unable to drive the entire load or a hard shutdown may happen when starting a high power load; if the capacity is too high, it will need high investment and maintenance costs and thus resulting in a waste of resources. Moreover, according to the characteristics of internal combustion engine, heavy carbon deposit in the engine piston rings and spark plugs, increasing cylinder wear, oil leakage and other serious problems will happen if it is operated under a low load for a long time. Relief starting or variable starting is usually used in this case.
There is inrush current, harmonic feedback, current mutation and other interferences during starting with non-linear load, which also have a relatively high pressure drop requirements on the genset. In this situation, it is best to choose a generator with auxiliary winding.
II. Auantity of frequently-used genset
At least two frequently-used diesel gensets should be equipped, so that they can be operated in turn during maintenance and service. This type of operation also requires that the gensets shall be able to operate in parallel so as to ensure continuous power supply and adaptation to the change of electricity load curve. With multiple units of gensets, it is able to determine how many units to put into operation based on the electricity load change, so that diesel engine is running under economic load to reduce fuel consumption and generation costs. The optimal economic status of diesel engine is running at 75%-90% of rated power. For occasions with higher power requirements, each device may be designed with a set of backup control system, what is more, there shall be seamless switching between the backup control system and the primary system to make sure no sudden power failure will happen. System diagram is generally as follows,
Two gensets in parallel operation
I. Capacity of frequently-used genset
The genset capacity eventually required by user is calculated on the basis that the output power of long-running genset can meet the calculated maximum load of the whole project. The type of load is usually one of the major considerations in selecting the genset capacity. Load is generally divided into: linear load (e.g., resistive load or inductive load) and non-linear load including rectifier circuit (also known as rectifier load).
The resistive load features nearly unchanged resistance, while current decreases with voltage proportionally. With this type of load, the genset is only required to have a capacity slightly higher than the load.
For inductive load (e.g., 3-phase squirrel-cage asynchronous motor), there is large current during startup, and the power factor is much less than its normal operating value. If it is started up directly, the starting current is 5-7 times that of normal operating, which means that the genset shall have enough capacity to meet the startup requirements. But as a frequently-used genset, it may turn out to be of too much power, since the normal operation power is much less than the genset’s rated power, which is obviously wasteful. If the capacity of the genset is too low, it would be unable to drive the entire load or a hard shutdown may happen when starting a high power load; if the capacity is too high, it will need high investment and maintenance costs and thus resulting in a waste of resources. Moreover, according to the characteristics of internal combustion engine, heavy carbon deposit in the engine piston rings and spark plugs, increasing cylinder wear, oil leakage and other serious problems will happen if it is operated under a low load for a long time. Relief starting or variable starting is usually used in this case.
There is inrush current, harmonic feedback, current mutation and other interferences during starting with non-linear load, which also have a relatively high pressure drop requirements on the genset. In this situation, it is best to choose a generator with auxiliary winding.
II. Auantity of frequently-used genset
At least two frequently-used diesel gensets should be equipped, so that they can be operated in turn during maintenance and service. This type of operation also requires that the gensets shall be able to operate in parallel so as to ensure continuous power supply and adaptation to the change of electricity load curve. With multiple units of gensets, it is able to determine how many units to put into operation based on the electricity load change, so that diesel engine is running under economic load to reduce fuel consumption and generation costs. The optimal economic status of diesel engine is running at 75%-90% of rated power. For occasions with higher power requirements, each device may be designed with a set of backup control system, what is more, there shall be seamless switching between the backup control system and the primary system to make sure no sudden power failure will happen. System diagram is generally as follows,
Two gensets in parallel operation
