summary
Switched Reluctance Drive: Summary
The Electrical Institut of the University Karlsruhe has developed, optimized and manufactured a Switched Reluctance Drive with power converter and control engineering according to the latest scientific findings. The motor was constructed for the rated output of 26 kW and for industrial applications. The drive works in all for quadrants and was designed for applications with highest demands for dynamics, constant torque, low noise and highest power output. The nominal speed of the test Switched Reluctance Motor is 1500 revolutions per minute. Cooling is obtained using an external blower, which blows air over the machine (cooling method IC416). The motor was built for continuous running duty and for both turn directions. The degree of protection is IP 54. Table 1 lists the technical data of the new 16/12 Switched Reluctance Motors in comparison with another Switched Reluctance Motor. The main components of the test drive are the Switched Reluctance Motor and the power converter. The voltage-source converter consists of mains and motor converter. The common supply for the three-phase-self-commutated mains converter is 400V/50Hz.
type: | CVEAA XM 132L | MFR 132.5 University Karlsruhe |
comparison |
rated output | 17 kW | 26 kW | improve to 152 % |
nominal speed | 1500 rpm | 1500 rpm | equal |
shaft height | 132 mm | 132 mm | equal |
length | 985 mm | 777 mm | reduce to 79 % |
weight | 178 kg | 165 kg | reduce to 93 % |
duty type | S1 | S1 | equal |
thermal class | H | H | equal |
cooling method | IC 416 | IC 416 | equal |
cooling fan | 250 W | 65 W | reduce to 26 % |
moment of inertia | 0,0892 kgm2 | 0,0883 kgm2 | |
number of phases | 3 | 4 | |
stator poles | 12 | 16 | |
rotor teeth | 8 | 12 |
Table 1: Technical data of the new 16/12 Switched Reluctance Motor in comparison with another Switched Reluctance Motor
Torque ripple
All converter-fed electric motors have a greater or lesser torque ripple on the generated main torque. An excessive torque ripple has limited the applications of Switched Reluctance Drives in servo systems. For these reasons we minimized this ripple with the motor model and the current control. The small torque ripple and its effect on the speed is shown in Figure 1. The torque ripple is smoothed only with the inertia moment of the Switched Reluctance Motor. In this simulation, the load inertia equals zero. Under these working conditions already, the speed is almost constant.
Figure 1: Torque ripple and its effect on the speed (simulation) J = 0,0883 kgm2
16/12 Switched Reluctance Motor and its speed control
The control has been optimized to minimize speed variations. The speed controller is a PI-controller. After a rated value jump of the speed, the measured speed does not swing over. The torque and current control are united in the speed control to a delay part of first order with a small time constant. After rise of the load torque by 100 Nm, the speed keeps within a tolerance band of 3 % (Figure 2).
Figure 2: The speed after rise of the load torque by 100 Nm (measurement) J = 0,54 kgm2
16/12 Switched Reluctance Motor and its position control
Likewise, the position control of, for example, workpieces, tools, conveyor baskets etc. belongs to the applications of electric motors. The measuring result in Figure 3 proves that Switched Reluctance Motors with 16 stator poles and 12 rotor teeth are suitable position drives. After a rated value jump of 1000°, the motor performs about 2,8 turns and reaches the rated value without over swing in one second.
Figure 3: Position control (measurement) J = 0,54 kgm2
Mains friendliness of the Switched-Reluctance-Drive
The mains converter is a three-phase-self-commutated IGBT-Converter. The control of the mains current has been optimized in a way that the drive, in stationary running with a cos(=1 and with a power factor of about one, receives energy from or feeds energy into the threephase current mains. This results in a sinusoidal mains current and in conformity of the phase position between current and voltage - at long last the mains friendliness of the drive.
Rotor for the 16/12 Switched Reluctance Motor