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Do You Understand What A Generator Series Is?

June 1, 2020

In the generator, the generator has a series. The number of stages here does not refer to the height of the generator, but refers to the synchronous speed of the generator. Let's take a 4-stage generator as an example to take a look at the specific meaning of the number of generator stages.

 

The 4-level generator refers to the synchronous speed of the generator for 1 minute = {frequency of power supply (50Hz) × 60 seconds} ÷ (number of motor stages ÷ 2) = 3000 ÷ 2 = 1500 rpm. In the factory, it is often heard that the generator is of several levels. To understand, the first thing to know is the concept of pole: pole refers to the magnetic pole formed by the generator rotor after the rotor coil is energized with excitation current. Simply put, each revolution of the rotor can induce several cycles in the stator coil to form a few cycles. The current has a different number of poles. To produce a 50hz potential requires different speeds. 50HZ60 minutes and minutes (ie 3000) divided by the number of poles is the number of revolutions per minute of the generator. The same is true for electric motors, only a reverse process of generators.

The number of poles reflects the synchronous speed of the motor. The 2-pole synchronous speed is 3000rmin, the 4-pole synchronous speed is 1500rmin, the 6-pole synchronous speed is 1000rmin, and the 8-pole synchronous speed is 750rmin. It can be understood as follows: 2 poles are cardinal (3000), 4 poles can only be divided by 2, 6 poles can be divided by 3, and 8 poles can be divided by 4. It's not that 2 poles have to be divided by 3000. The more pole pairs of the motor, the lower the generator speed, but the greater the torque; when choosing a generator, you need to consider how much starting torque the load needs, such as the start with load The torque required for no-load starting is large. If it is a high-power and large-load start, you must also consider the step-down start (or star-delta start); as for the problem of matching the speed of the load after determining the number of generator pole pairs, you can consider using different diameter pulleys to drive or use Gearing (gear box) to match. If the power requirement of the load cannot be reached after the number of pole pairs of the generator is determined through a belt or gear drive, then the power usage of the generator must be considered.

 

The three-phase alternator is mainly composed of a stator and a rotor. When three-phase alternating current flows into the stator, a rotating magnetic field is generated. The magnetic field always has two poles (which can also be said to appear in pairs), namely the N pole (north pole) and the S pole (south pole), also known as a counter pole. When the winding method of the alternator stator winding is different, the number of magnetic poles of the generated rotating magnetic field is different. The number of magnetic poles directly affects the speed of the generator. Their relationship is: synchronous speed = 60 × logarithm of the frequency level. If the synchronous speed of the generator is 1500 rpm, the number of pole pairs can be calculated according to the above formula, which is a 4-pole generator. The synchronous speed and the number of pole pairs are the basic parameters of the generator, which can be found on the nameplate of the generator. Because the number of pole pairs can affect the speed of the generator, the speed of the generator can be changed by changing the number of pole pairs of the generator.

 

For fluid loads such as fans and pumps, this type of load has a more prominent feature. In the colloquial term, it is called resistance to mutation, which means that such a load has a great resistance to the current mutation. Although the torque required to promote this type of load change is not high, but it requires a lot of energy to change the status quo more quickly, just like boiling water, a small fire can also be boiled. The fire will be great.

 

These are the specific descriptions of the generator stages. For a given frequency university and starting current size, the two are not necessarily related. The magnitude of the starting current actually depends on the setting of the starting VF curve and the length of the acceleration time. For fluid loads, the use of multiple power curves can make the equipment run more energy-efficient, thereby obtaining more economic benefits.