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A braking chopper is an magnetical switch that limits the DC bus voltage by switching the braking energy to a resistor where the braking energy is converted to heat. Braking choppers are automatically activated when the actual DC bus voltage exceeds a specified level depending on the nominal voltage of the variable-frequency drive
Schematic of an inverter using a vibrator as a chopper. In electronics, a chopper circuit is any of numerous types of electronic switching devices and circuits used in power control and signal applications. A chopper is a device that converts fixed DC input to a variable DC output voltage directly.
A DC injection brake system can be used as an alternative or addition to a friction brake system. DC injection brakes only require a small module located with the other motor switchgear and/or drivers, mounted in a remote and convenient location, whereas a friction brake must be mounted somewhere on the rotating system.
The use of both braking systems at the same time is called blended braking. Li-ion batteries have also been used to store energy for use in bringing trains to a complete halt. [1] Although blended braking combines both dynamic and air braking, the resulting braking force is designed to be the same as the air brakes on their own provide.
The circle diagram can be drawn for alternators, synchronous motors, transformers, induction motors. The Heyland diagram is an approximate representation of a circle diagram applied to induction motors, which assumes that stator input voltage, rotor resistance and rotor reactance are constant and stator resistance and core loss are zero.
To release the brakes, the engineer charges the brake pipe. This method of controlling the brakes on freight and passenger cars has remained virtually unchanged since its invention by George Westinghouse in 1868. The conventional braking system suffers from many weaknesses; one of which is in the reaction time. Because the engineer controls the ...
In vector control, an AC induction or synchronous motor is controlled under all operating conditions like a separately excited DC motor. [21] That is, the AC motor behaves like a DC motor in which the field flux linkage and armature flux linkage created by the respective field and armature (or torque component) currents are orthogonally aligned such that, when torque is controlled, the field ...
Any dynamic braking operation required for the motor can be realized by means of braking DC chopper and resistor shunt connected across the rectifier. Alternatively, an anti-parallel thyristor bridge must be provided in the rectifier section to feed energy back into the AC line.