High-speed motors are often limited by heat-sensitive components to avoid thermal destruction. In the caused by frequency inverter engine warming has the Lüneburg Sieb + Meyer AG and devices designed with a regulated DC link. They allow for heat-reduced top speed. In this application area In addition to the actual engine performance, the engine heating caused by the frequency converter plays a functionally critical role.
Compared with slow-speed motors, the high-speed devices have a much smaller rotor volume. As a result, the conditions for heat absorption or radiation are correspondingly lower. As a result, a higher rotor heating occurs - with the same occurring engine losses. However, this can quickly lead to a thermal destruction of the motors.
For this reason, the drive specialist in the product series SD2S and SD2T offers a converter topology with controlled DC link and pulse amplitude modulation (PAM). The difference to the conventional design with fixed intermediate circuit voltage and pulse width modulation (PWM) of the clocked power output stage lies in the additional regulated DC / DC converter; it allows variable control of the DC link voltage. In combination with the PAM, an output voltage can be supplied whose voltage level is independent of the rotating field frequency.
The block-shaped output voltage has only minor low-frequency harmonic current components, the motor inductance is fully effective. This reduces the inverter-related engine losses so much that it is possible to dispense with external motor chokes completely. There is virtually no limitation with respect to the possible rotating field frequency since it corresponds to the final stage clocking in each case. The motor is only loaded with the voltage defined for the operating point, so that lower harmonics occur especially at lower speeds. This results in less engine heating. Due to the very low switching frequency, problems with electromagnetic compatibility (EMC) or motor insulation are not to be feared. Instead of either-or can be achieved by the engine and power electronics equally a very good efficiency.