SU1181047A1 - Device for open-phase protection of three-phase motor powered from frequency converter - Google Patents

Abstract

DEVICE FOR PROTECTION OF PHASE MOTOR FED INVERTER FROM, TO BREAK phase containing included primary windings in three motor phase current transformer, the secondary windings of which through the zener diodes, rectifiers and capacitors integrable guides operatively associated with the AND-NO elements, and, ШШ, with an amplifier and an actuator connected to its output, a voltage transducer of a frequency converter connected by an input to a frequency converter, characterized in that, in order to achieve increase the reliability of protection; an INI element is connected to the integrating capacitors by inputs and parallel to it 3. the element ШШ, the outputs of which, as well as the output of the voltage sensor of the frequency converter, are connected to the inputs of the element I. and between its output and amplifier there is included an additionally introduced element of time.

Description

The invention relates to electrical engineering and can be used to protect induction motors powered from frequency conversion / oil from the hard phase.

The purpose of the invention is to simplify and increase the reliability of protection of a three-phase motor against phase loss.

The drawing shows a schematic diagram of a device for protecting a three-phase electric motor powered from a frequency converter against phase loss.

The proposed device contains a switching device 1, a frequency converter 2, a protected motor 3, 4-phase current transformers 4-6, zener diodes 7-9, rectifiers 10-12, integrating capacitors 13-15, voltage converter 16, I-NE element 17, element OR 18, element AND 19, e-lementa 20 time delay, amplifier 21, 1 executive organ 22.

The device works as follows.

Current transformers 4-6 convert the primary current flowing in the phases of the motor 3 into a voltage which, after being limited to zener diodes 7-9, rectified by diode bridges 10-12 and smoothed by capacitors 13-15, is fed to a protection logic circuit. At the same time, the logic circuit consisting of elements 17-20 is supplied with voltage from voltage sensor 16 of the frequency converter. At the output of the circuit, depending on the combination of incoming signals, a low voltage level is formed, corresponding to a logical .O, or a high voltage level, corresponding to a logical 1. At a voltage equal to logical 1, the signal goes through the amplifier 21 and the actuator 22 to the switching device one.

In the initial disconnected state, at the output of the sensor 16 is w o, at the input of the element AND-NOT 17 and the element OR 18 - three O, at the output of the element AND-NOT 1, at the output of the element W)

at the output of the element I 19 Oh, at the output of the element 20 O.

When the engine is started up, switching device 1 is turned on, voltage is applied to frequency converter 2, and from it the voltage and frequency associated with a certain ratio are applied to engine 3. The engine is accelerated to operating speed. At the time of start-up, at the output of the sensor 16 there is 1, at the input of the element AND-NOT 17 and the element OR 18 - three 1, at the output of the element AND-NO O, at the output of the element OR 1, at the output of the element AND 19 O, at the output of the element 20 O. A similar state of the logic circuit during normal engine operation.

During engine braking, the voltage is removed from the frequency converter by the control circuit. At the output of sensor 16, there is O at the input of the elements AND-HE 17 and OR 18 — two 1 and one O, at the output of the element AND-NOT 1, at the output of the element OR 1, at the output of the element AND 19 O, at the output of the element 20 O.

During normal operation and short-term failure in one of the phases at the output of the sensor 16 1, at the input of the elements AND-NOT 17 and OR 18 - two 1 and one O, at the output of the element AND-NOT 1, at the output of the element OR 1, at the output of the element And 19 1, at the output of element 20 due to a short-term failure of O

When the engine is running and the break of one of the phases at the output of the sensor 16 1, at the input of the elements AND-NOT 17 and OR 18 is two 1 and one O, at the output of the element IS-NOT 1, at the output of the element OR 1, at the output of the element And 19 1 , at the output of the element 20 due to the long duration of the half-phase mode 1. The signal arrives at the input of the amplifier, and from it - to the executive body 22 and the switching device 1. The damaged engine is disconnected.

The proposed device is easier to perform than the known, more reliable, since it can be rebuilt in time from short-term malfunctions in the operation of regulating devices

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Claims (1)

A DEVICE FOR PROTECTING A THREE-PHASE ELECTRIC MOTOR, SUPPLY FROM A FREQUENCY CONVERTER, FROM A PHASE Breakage, containing three current transformers included in the primary phases of the electric motor phases, the secondary windings of which are connected through the zener diodes, rectifiers and integrating AND, which are NOT functionally connected to an amplifier and an actuator connected to its output, a voltage sensor of the frequency converter connected to the input of the frequency converter, characterized in that, in order to simplify and increase Nia protection reliability, the integrating capacitor connected to inputs of AND-NO element and parallel to an OR gate, the outputs of which, as well as the inverter output voltage frequency sensor connected to the inputs VI element and between its outlet hours amplifier included additionally inputted time element. 1 1181047 2