Wuxi Lanhai Electric Motor Co.,Ltd
Add: 4#, Tianshi Road Shitangwan Town, Wuxi, Jiangsu, China
Asynchronous Motor direct start current is too large
In the three-phase asynchronous Motor start-up process, we often want to have enough large starting torque, but the starting circuit should not be too large to meet the various mechanical properties while reducing the impact on the grid, but in practice these two requirements contradictory. For squirrel-cage Motor direct start, the starting current multiple of 4 to 7, while the starting torque multiplier only 0.9 to 1.3, start performance is not good.
Direct start, also known as full pressure start, that is, with the ordinary switch to the AC Motor directly into the power grid. The larger the capacity of the power supply transformer, the smaller the system bus voltage caused by the starting current, allowing direct start-up as long as the rated voltage is not exceeded (10% to 15%).
Asynchronous Motor direct start will have the following adverse effects:
(1) to reduce the grid voltage and affect other electrical equipment
(2) the Motor overheating and accelerated insulation aging
(3) excessive electromagnetic force shock to the Motor stator winding end deformation
Can be directly on the asynchronous Motor to start the current problem is too large how should we solve? Power greater motor starting current is very large, if multiplied by 4 to 7 times, the power grid will be a great impact. In practice, most manufacturers use the following methods to asynchronize the Motor directly to start the current is too large to reduce the starting current.
(1) to reduce the power supply voltage (that is, step-down start, common, such as star delta start: start, the stator winding connected to the star, reducing the stator winding voltage; start is completed, into a triangle, with autotransformer start: Input autotransformer, reduce the stator winding voltage; start up, remove the autotransformer.)
(2) increase the set, the rotor impedance (start in the stator circuit in the string into the reactor, from the sub-pressure to reduce the voltage, reduce the starting current; start is complete, remove the reactor.)
Three-phase asynchronous Motor in the course of the use of the Motor sometimes do not touch the situation, whether the motor has been burned? Missing or shorted? Is the bearing broken? The following small series to introduce you to the common Motor does not turn the reasons and check the method.
The Motor does not turn the following symptoms and causes and solutions:
1, the Motor does not turn nor sound. The reason for this symptom may be that the Motor power or winding has two or three phases. First check if there is a supply voltage. Such as the three-phase no voltage, indicating the fault in the circuit, then by measuring the Motor three-phase winding resistance to find the phase of the winding; if the three-phase voltage balance, then the fault in the Motor itself.
2, the Motor does not turn, but the "buzzing" sound. At this point should be measured Motor terminal, such as three-phase voltage balance and rated as a serious overload.
Check the steps
First remove the load, if the Motor speed and sound normal, you can determine the Motor overload or load part of the mechanical failure. If you still do not turn, you can turn the Motor shaft by hand, if it is tight or not fixed, then measured three-phase current, such as three-phase current balance, but greater than the rated value is likely to be mechanical part of the Motor was stuck, Lack of oil, bearing rust or serious damage, the end cap or oil cover is too rampant, the rotor and the chamber collided (also known as sweeping bore). If the hand rotation of the Motor shaft to a certain angle feel more difficult or hear the cyclical "Cha Cha" sound, can be judged as sweeping chamber. The reasons are:
(1) bearing between the outer ring is too large, need to replace the bearing;
(2) bearing chamber (bearing hole) is too large, long-term wear caused by the hole diameter is too large. Emergency measures are electroplating a layer of metal or a set of sets, but also in the bearing chamber wall with some small points;
(3) axis bending, end cap mouth wear.
In addition to these electrical problems, the Motor does not turn the reasons there are willing to be mechanical failure, such as bearing damage, etc., this time should be replaced bearings, this time you can view the Motor bearing model, if not sure, you can contact the original Motor manufacturers.