Introduction
Motor starting current is a crucial parameter to consider in any industrial or commercial setting that relies on electric motors for its operations. When an electric motor starts up, it can draw a current that is significantly higher than its regular running current. This sudden surge of electricity is often many times the motor's rated full-load current, which can result in a host of issues. These may include undue mechanical stress on the motor itself, increased wear and tear on equipment, and electrical stress on the power distribution system.
Moreover, high starting currents can also lead to inefficiencies that contribute to higher operational costs and, in some cases, may even trip circuit breakers or blow fuses, causing downtime.
Given these challenges, finding ways to effectively reduce motor starting current has become a subject of prime importance. This article aims to serve as a guide, offering five actionable tips to lower the starting current of electric motors without compromising their performance.
Whether you are an engineer, a maintenance technician, or a facility manager, these tips will help you optimize your systems for both performance and long-term sustainability.
So, let's dive in and explore these tips in detail.
Direct start
Direct start is to connect the stator winding of motor directly to the power supply and start at rated voltage, which is characterized by large starting torque and short starting time, and it is also the simplest, the most economical and the most reliable starting method.
Full-voltage starting current is large, but the starting torque is not large, easy to operate, start quickly, but this starting method of grid capacity and load requirements are relatively large, mainly for 1W below the motor start.
Series resistance starting
Motor series resistance start, which is also a method of reduced voltage start. In the starting process, the stator winding circuit in series resistance, when the starting current through, the resistance on the voltage drop, reducing the voltage added to the stator winding above, so you can achieve the purpose of reducing the starting current.
Autotransformer start
The use of autotransformer multi-tap voltage reduction, not only can adapt to the needs of different load starting, but also can get a larger starting torque, is often used to start a larger capacity motor voltage reduction starting method. Its biggest advantage is that the starting torque is larger, when the winding tap is at 80%, the starting torque can reach 64% of the direct starting, and the starting torque can be adjusted by the tap.
Star-delta reduced voltage starting
For normal operation of the stator winding for the triangular connection of the squirrel cage asynchronous motor, if the stator winding is connected to the star during the start, to be connected to the triangle after the completion of the start, you can reduce the starting current, reduce its impact on the grid.
Such a starting method is called star-delta reduced voltage starting, or simply star-delta starting (y-& starting). Star-delta starting, starting current is only 1/3 of the original direct starting method according to the triangle connection. in the star-delta starting, starting current is only 2-2.3 times.
That is to say, when using star-delta starting, the starting torque is also reduced to 1/3 of the original direct starting according to the delta connection, which is suitable for the occasion of no-load or light-load starting.
And compared with any other reduced voltage starter, its structure is the simplest, the price is also the cheapest. In addition, the star-delta starting method has another advantage, that is, when the load is light, the motor can be allowed to run under the star connection. At this time, the rated torque and the load can be matched, which can make the efficiency of the motor is improved, and because of which the power consumption is saved.
Inverter start (soft start)
Frequency converter is the motor control device with the highest technical content, the most complete control function and the best control effect in the field of modern motor control, which regulates the speed and torque of the motor by changing the frequency of the power grid.
Because it involves power electronic technology and microcomputer technology, it has high cost and high requirement for maintenance technicians, so it is mainly used in the field which needs speed regulation and has high requirement for speed control.
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