There are many types of motor load on the motor test system on the market, such as eddy current brake load, magnetic powder brake load, hysteresis brake load, servo motor load and so on. Considering the characteristics and cost of the motor under test, it is important to choose a suitable load. How can we choose the load of a suitable electrical test platform?
First, let's understand the characteristics and working principle of each type of load brake:
First, the eddy current brake
The eddy current brake is a domestic advanced analog loading device, which is mainly used to simulate the output performance of various power devices, and is composed of an induction disk, an armature and an excitation part. When the exciting coil coaxially mounted with the rotor is DC-powered, the magnetic flux generated by it forms a closed loop through the armature body, the swirl ring, the air gap and the rotor. Since the outer circular surface of the rotor is formed with evenly distributed teeth and grooves, a magnetic field between the air gap and the armature body or the vortex ring surface is generated, so that the armature body and the swirl ring are rotated by the rotor. The magnetic field at any point on the inner surface is called a change, thereby inducing a "vortex", and under the coupling of the "eddy current" and the magnetic field, a braking torque is generated on the rotor. Since the armature body is fixed on the bottom plate through the base, the rotor cannot drive the armature body to rotate, and the power output of the power machine is converted into the equivalent heat generated by the "eddy current" on the armature body and the vortex ring, and the heat is entered. The armature and vortex ring cool the continuous cooling water in the water tank and the eddy current brake itself. Corresponding to each constant current of the exciting coil, the eddy current brake exhibits a stable braking characteristic curve with a torque attached to the rotating speed, and the braking torque can be changed by changing the magnitude of the exciting current.
Second, the magnetic powder brake
The magnetic powder brake is a new type of transmission component that uses magnetic powder as a medium to form a magnetic powder chain to transmit torque under energization. It consists of an inner rotor, an outer rotor, an excitation coil and a magnetic powder. When the coil is not energized, the active rotor rotates. Due to the centrifugal force, the magnetic powder is clamped on the inner wall of the active rotor, and there is no contact between the magnetic powder and the driven rotor, and the active rotor idles. After the DC power is turned on, an electromagnetic field is generated, and the magnetic powder of the working medium forms a magnetic powder chain under the action of the magnetic force line, and the inner rotor and the outer rotor are coupled to achieve the purpose of transmitting and braking torque. It can transmit a certain torque regardless of slip, and has the advantages of fast response, simple structure, no pollution, no noise, no impact vibration and energy saving.
Third, the magnetic hysteresis brake
The hysteresis brake is composed of two parts: a rotor and a stator pole. The rotor is made of a special hysteresis material. The stator pole has a certain gap and the rotor rotates in the gap. When the coil is energized, a magnetic field is generated in the gap, causing a hysteresis effect on the rotor. When the hysteresis rotor is rotated against the hysteresis force under the action of an external force, the rated torque is generated. The torque is only related to the magnitude of the excitation current, independent of the speed, enabling non-contact torque transmission.
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