Asynchronous motor starting problem is that it's a special problem in running. The commonly used methods are all direct starting, auto voltage reducing starting, Y - Δ starting, soft starting,
starting, etc. Automatic decompression star delta starter control circuit However, large starting
current, especially how much has the large capacity motor or electric motor needs to start at the
same time,
www.dongfeng-motor.com great influence to power grid. For medium and small capacity of power grid, for example, large starting current will cause a big line pressure drop, and thus affect the power grid of the power supply quality auto voltage step-down start principle. Serious when, can even affect the normal operation of other electrical equipment in the power grid. It goes without saying that large starting current can result in considerable online road and the motor itself active power loss. Especially in the acceleration torque is small, load torque moment of inertia of the unit and larger, and starting and very frequent, this factor is more nots allow to ignore. Again, direct
starting is large starting torque, for the good of heavy load, but for the general light load, it is
possible to mechanical shock occurs, leading to drive belt torn, the gear was destroyed. So while
starting method is simple, direct starting equipment is simple, cheap, but in order to limit the
impact of the electrical and mechanical, and ensure the quality of the grid power supply, on some
occasions, decompression starting ways, or in series with wound rotor asynchronous motor rotor
circuit impedance for starting. Principle by a motor, the motor starting current is proportional to
the IQ in the terminal voltage of the motor, so reduce the terminal voltage, can make the starting
current is reduced proportionately.
the starting current to full voltage starting at 1 / k. So, seems to reduce the terminal voltage of
the motor is reduced when starting current impact, thus tz effective measures to solve the problem of
asynchronous motor starting, and voltage to reduce more to start the better. Actually it doesn't have to be. Because in the terminal voltage of the motor rated voltage reduce to 1 / k, although the
starting current is reduced to full voltage start 1 / k, but at the same time, the starting torque of
the motor is reduced, and it is according to the proportion of 1 / k2 greatly reduced, what's more,
starting when the power factor of drops will also aggravate the situation.
asynchronous motor Therefore, must not
simply think that reduce the voltage of the motor is a feasible way of starting anywhere. Star triangle starting in two aspects of power grid and load are allowed total pressure directly under the condition of starting, squirrel-cage asynchronous motor with direct starting advisable, convenient for operation control, and more economic. Autoformer decompression starter is often used to starting large capacity squirrel-cage asynchronous motor starting device for stress relief. Although autoformer decompression starter is an old-fashioned starting equipment, but using the autotransformer tapped the reduced pressure, can adapt to the needs of different load starting, and can get a bigger starting torque, and also due to furnish have thermal relay and low voltage trip and has a perfect protection of overload and voltage-absent, therefore, are still widely used. For the normal operation of the stator winding for delta connection squirrel-cage asynchronous motor, if at the time of starting the stator windings into star, waiting for start to end to connect into a
triangle, can reduce the starting current, to reduce its impact on the grid. Such starting way is
called star triangle decompression starting, or simply the star delta starter (Y - Δ starter).
