| 摘要 |
The invention concerns a method for operating an electronically commutated motor (10) that is equipped with a current limiting arrangement which acts on a PWM controller (56). The latter, in operation, delivers PWM pulses (60) having a controllable pulse duty ratio (pwm) and a substantially constant frequency. In the event a predetermined upper limit value (Isoil; Iw) of the motor current (Iist) is exceeded, the current limiting arrangement effects a change in this pulse duty factor (pwm) in order to reduce the motor current (Iist). If the motor current (Iist) exceeds a predetermined upper limit value (Isoil; Iw) while the motor (10) is rotating, that limit value (Isoil; Iw) is raised by a timing member (260) during a predetermined time span (304) (FIG. 8: Iwmax), so that the available motor power is temporarily raised in the context of a load peak. If the rotor (24) is stalled, the limit value (Isoil) is not raised but instead is greatly lowered. The limit value (Isoil) is preferably raised as a function of the rotation speed of the motor (10) in order to utilize the improved motor cooling at high rotation speeds. At start-up of the motor (10), the limit value (Isoil) is briefly increased to a high value in order to enable dependable starting.
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