JPS5563589A - Emergency stopping device for variable speed induction motor - Google Patents

Abstract

PURPOSE: To protect a driving circuit from burning and other damage, by closing a contact on a DC damping circuit of an induction motor by an 'Emergency Stop Command' and opening it after elapsing of a fixed period of time, so that a current limiting resistance of the DC damping circuit can be prevented from generation of heat.

CONSTITUTION: During normal operation, contacts r₁₁ through r₁₃ are closed and contacts r₂₁ through r₂₂ are opened, and an electric motor 4 is connected to a power inverter 3 and driven at a speed in accordance with a 'Speed Command' VEC put into a power inverter driving circuit 5. In the case of an emergency stop, the contacts r₁₁ through r₁₃ are opened and the contacts r₂₁ and r₂₂ are closed, and DC voltage put out from a power converter 2 through a DC damping circuit 6 having a current limiting resistance R is impressed on the electric motor 4 for DC damping operation. Upon elapsing of closing time of the contacts r₂₁ and r₂₂, which was conformed with the time required for the electric motor 4 to satisfactorily reduce its speed or to stop completely, by opening of the contacts r₂₁ and r₂₂, the electric motor 4 is separated from the DC damping circuit 6. And therefore, it is possible for the current limiting resistance R to avert from heat generation and power loss, etc.

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