Variable frequency control device for booster pump motor of steam turbine oil cooler pipeline

Abstract

The utility model belongs to the technical field of motor control circuits, and particularly relates to a steam turbine oil cooler pipeline booster pump motor frequency conversion control device. Comprising a frequency converter main circuit which comprises a circuit breaker QF1, a frequency converter and a contactor KM1; the three-phase power supplies L11, L21 and L31 are connected to the input ends R, S and T of the frequency converter through normally open contacts of the circuit breaker QF1, and the output ends U, V and W of the frequency converter are connected to the motor M through normally open contacts of the contactor KM1; the power frequency bypass circuit comprises a circuit breaker QF2, a contactor KM2 and an overload protection relay KH; the three-phase power supplies L11, L21 and L31 are connected to the input end of the overload protection relay KH through a normally open contact of the circuit breaker QF2, and the output end of the overload protection relay KH is connected to the motor M; by performing frequency conversion transformation on the motor, the current of the motor is reduced, the energy-saving requirement is met, meanwhile, the stability and reliability of motor operation are improved, and efficient operation of a power generation system is guaranteed.

Description

Technical Field

[0001] This utility model belongs to the field of motor control circuit technology, and specifically relates to a frequency conversion control device for a booster pump motor in a steam turbine oil cooler pipeline. Background Technology

[0002] In thermal power generation systems, the turbine oil cooler pipeline booster pump motor currently operates in power frequency mode. This operating mode has many drawbacks: on the one hand, the motor lacks adjustment capability, often resulting in excessive output. Currently, excess output is usually adjusted by opening the bypass valve, but this method has poor energy-saving effect; on the other hand, prolonged power frequency operation will cause the motor temperature to become too high, which not only increases energy consumption but also affects the motor's service life and stability, posing a potential threat to the safe and stable operation of the entire power generation system. Utility Model Content

[0003] The purpose of this utility model is to provide a frequency conversion control device for the motor of the booster pump in the pipeline of a steam turbine oil cooler. It aims to solve the problems of excessive output, poor energy-saving effect and high motor temperature when the motor of the booster pump in the pipeline of a steam turbine oil cooler is running at the power frequency. By modifying the motor with frequency conversion, the motor current is reduced to meet the energy-saving requirements, while improving the stability and reliability of the motor operation and ensuring the efficient operation of the power generation system.

[0004] To solve the above-mentioned technical problems, this utility model provides a frequency conversion control device for the motor of the booster pump in the pipeline of a steam turbine oil cooler, comprising:

[0005] The main circuit of the frequency converter includes a circuit breaker QF1, a frequency converter, and a contactor KM1; three-phase power supplies L11, L21, and L31 are connected to the input terminals R, S, and T of the frequency converter through the normally open contacts of the circuit breaker QF1, and the output terminals U, V, and W of the frequency converter are connected to the motor M through the normally open contacts of the contactor KM1.

[0006] The power frequency bypass circuit includes circuit breaker QF2, contactor KM2, and overload protection relay KH; the three-phase power supplies L11, L21, and L31 are connected to the input terminal of overload protection relay KH through the normally open contact of circuit breaker QF2, and the output terminal of overload protection relay KH is connected to motor M.

[0007] The control circuit includes a remote frequency conversion control circuit, a local frequency conversion control circuit, and a local power frequency control circuit; the remote frequency conversion control circuit and the local frequency conversion control circuit are switched via a changeover switch SA1; the local frequency conversion control circuit and the local power frequency control circuit are switched via a changeover switch SA2.

[0008] Preferably, the control circuit further includes a frequency converter main control circuit, which includes: a control power supply U11, a neutral line N, a fuse FU4, relays KA2-KA5, a time delay relay KT, a power indicator light 1XD, a cooling fan KP1, a frequency converter running indicator light 2XD, a frequency converter stop indicator light 3XD, and a frequency converter fault indicator light 4XD; one end of the power indicator light 1XD is connected to the control power supply U11 through the fuse FU4, and the other end is connected to the neutral line N; the fuse FU4 is connected to the normally closed contact of contactor KM1, the coil of contactor KM1, and the neutral line N in sequence through the normally open contact of relay KA2; the fuse FU4 is connected to the normally closed contact of contactor KM1, the coil of contactor KM1, and the neutral line N through relay KA2; the fuse FU4 is connected to the normally closed contact of contactor KM1, the coil of contactor KM1, and the neutral line N in sequence ... The normally open contact of electrical appliance KA3 is sequentially connected to the coil of time delay relay KT and the neutral line N; and the output terminals of the normally open contacts of relays KA2 and KA3 are connected. The fuse FU4 is sequentially connected to the inverter stop indicator 3XD and the neutral line N through the normally closed contact of contactor KM1; the fuse FU4 is sequentially connected to the cooling fan KP1 and the neutral line N through the normally open contact of contactor KM1; the fuse FU4 is sequentially connected to the inverter operation indicator 2XD and the neutral line N through the normally open contact of relay KA5; and the fuse FU4 is sequentially connected to the inverter fault indicator 4XD and the neutral line N through the normally closed contact of relay KA4.

[0009] Preferably, the remote frequency conversion control circuit specifically includes: contact 1 of changeover switch SA1 is connected to control power supply U11 through fuse FU4; contact 2 of changeover switch SA1 is connected in sequence to remote control stop signal, coil of relay KA1 and neutral line N; contact 2 of changeover switch SA1 is also connected in sequence to normally closed contact of relay KA1, remote control start signal, coil of relay KA2 and neutral line N; and normally open contact of relay KA2 is connected in parallel at both ends of the remote control start signal.

[0010] Preferably, the local frequency conversion control circuit specifically includes: the contact 3 of the changeover switch SA1 is connected to the control power supply U11 through the fuse FU4; the contact 4 of the changeover switch SA1 is sequentially connected to the contact 1 of the changeover switch SA2, the contact 2 of the changeover switch SA2, the switch button 1SB1, the switch button 1SB2, the coil of the relay KA3 and the neutral line N; and the two ends of the switch button 1SB2 are also connected in parallel to the normally open contact of the relay KA3.

[0011] Preferably, the local power frequency control circuit specifically includes: the contact 3 of the changeover switch SA2 is connected to the control power supply U21 through the fuse FU5, and the contact 4 of the changeover switch SA2 is connected in sequence to the switch button 2SB1, the switch button 2SB2, the normally closed contact of the overload protection relay KH, the normally closed contact of the contactor KM1, the coil of the contactor KM2 and the neutral line N.

[0012] Preferably, the two ends of the switch button 2SB2 also include normally open contacts of contactor KM2 connected in parallel, and the two ends of the coil of contactor KM2 also include power frequency operation indicator 5XD connected in parallel; one end of power frequency stop indicator 6XD is connected to fuse FU5 through the normally open contact of contactor KM2, and the other end is connected to neutral line N; one end of power frequency overload indicator 7XD is connected to fuse FU5 through the normally open contact of overload protection relay KH, and the other end is connected to neutral line N.

[0013] Preferably, the circuit further includes a current measurement circuit and a voltage measurement circuit; the current measurement circuit includes three current transformers and three ammeters; each current transformer is connected in series with an ammeter to form a measurement branch, and the three measurement branches are connected in parallel for measuring the current of the three-phase power supplies L11, L21, and L31; the voltage measurement circuit includes a changeover switch SA and a voltmeter; contacts 1 and 3 of the changeover switch SA are connected to the three-phase power supply L11 through fuse FU1, and a voltmeter is connected in series between contacts 2 and 4 of the changeover switch SA; contacts 5 and 7 of the changeover switch SA are connected to the three-phase power supply L21 through fuse FU2, and a voltmeter is connected in series between contacts 6 and 8 of the changeover switch SA; contacts 9 and 11 of the changeover switch SA are connected to the three-phase power supply L31 through fuse FU3, and a voltmeter is connected in series between contacts 10 and 12 of the changeover switch SA.

[0014] Preferably, the frequency converter further includes analog input terminals AI1+ and AI1-, and analog output terminals AO1+, AO1- and AO2+, AO2-.

[0015] Compared with the prior art, this utility model has the following advantages:

[0016] 1. Significant energy saving effect: Through frequency conversion modification, the motor current is reduced, avoiding energy waste caused by adjusting the bypass door when there is excess output, thus meeting the energy saving target and reducing the power generation cost.

[0017] 2. Improved motor stability: It solves the problem of excessively high motor temperature during long-term power frequency operation, extends the motor's service life, improves the stability of motor operation, reduces the risk of power generation system downtime due to motor failure, and ensures the safe and stable operation of the power generation system.

[0018] 3. Simple and flexible operation: The newly added control logic circuit and the power frequency start control circuit in the local control cabinet make the operation of the motor simpler and more flexible. It can be controlled remotely by frequency conversion or started locally by power frequency, which facilitates the operation and maintenance of the staff. Attached Figure Description

[0019] Figure 1This is a circuit diagram of a frequency conversion control device for a booster pump motor in a steam turbine oil cooler pipeline, which is part of this utility model.

[0020] Figure 2 This is the circuit diagram of the control circuit of this utility model.

[0021] Figure 3 This is the circuit diagram of the current measurement circuit of this utility model.

[0022] Figure 4 This is the circuit diagram of the voltage measurement circuit of this utility model. Detailed Implementation

[0023] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. The advantages and features of the present invention will become clearer from the following description. It should be noted that the drawings are all in a very simplified form and use non-precise proportions, and are only used to facilitate and clarify the illustration of the embodiments of the present invention.

[0024] like Figures 1-4 As shown, this utility model embodiment provides a frequency conversion control device for a turbine oil cooler pipeline booster pump motor, comprising:

[0025] The main circuit of the frequency converter includes a circuit breaker QF1, a frequency converter, and a contactor KM1; three-phase power supplies L11, L21, and L31 are connected to the input terminals R, S, and T of the frequency converter through the normally open contacts of the circuit breaker QF1, and the output terminals U, V, and W of the frequency converter are connected to the motor M through the normally open contacts of the contactor KM1.

[0026] The power frequency bypass circuit includes circuit breaker QF2, contactor KM2, and overload protection relay KH; the three-phase power supplies L11, L21, and L31 are connected to the input terminal of overload protection relay KH through the normally open contact of circuit breaker QF2, and the output terminal of overload protection relay KH is connected to motor M.

[0027] The control circuit includes a remote frequency conversion control circuit, a local frequency conversion control circuit, and a local power frequency control circuit; the remote frequency conversion control circuit and the local frequency conversion control circuit are switched via a changeover switch SA1; the local frequency conversion control circuit and the local power frequency control circuit are switched via a changeover switch SA2.

[0028] The control circuit also includes a frequency converter main control circuit, which includes: a control power supply U11, a neutral line N, a fuse FU4, relays KA2-KA5, a time delay relay KT, a power indicator light 1XD, a cooling fan KP1, a frequency converter running indicator light 2XD, a frequency converter stop indicator light 3XD, and a frequency converter fault indicator light 4XD. One end of the power indicator light 1XD is connected to the control power supply U11 through the fuse FU4, and the other end is connected to the neutral line N. The fuse FU4 is connected to the normally closed contact of contactor KM1, the coil of contactor KM1, and the neutral line N in sequence through the normally open contact of relay KA2. The fuse FU4 is connected to the normally closed contact of contactor KM1, the coil of contactor KM1, and the neutral line N through relays KA2 and KA5. The normally open contact of KA3 is connected sequentially to the coil of the time-delay relay KT and the neutral line N; and the output terminals of the normally open contacts of relays KA2 and KA3 are connected. The fuse FU4 is connected sequentially to the inverter stop indicator 3XD and the neutral line N through the normally closed contact of contactor KM1; the fuse FU4 is connected sequentially to the cooling fan KP1 and the neutral line N through the normally open contact of contactor KM1; the fuse FU4 is connected sequentially to the inverter run indicator 2XD and the neutral line N through the normally open contact of relay KA5; and the fuse FU4 is connected sequentially to the inverter fault indicator 4XD and the neutral line N through the normally closed contact of relay KA4.

[0029] The remote frequency conversion control circuit specifically includes: contact 1 of changeover switch SA1 is connected to control power supply U11 through fuse FU4; contact 2 of changeover switch SA1 is connected in sequence to remote control stop signal, coil of relay KA1 and neutral line N; contact 2 of changeover switch SA1 is also connected in sequence to normally closed contact of relay KA1, remote control start signal, coil of relay KA2 and neutral line N; and normally open contact of relay KA2 is connected in parallel at both ends of remote control start signal.

[0030] The local frequency conversion control circuit specifically includes: the contact 3 of the changeover switch SA1 is connected to the control power supply U11 through the fuse FU4; the contact 4 of the changeover switch SA1 is connected in sequence to the contact 1 of the changeover switch SA2, the contact 2 of the changeover switch SA2, the switch button 1SB1, the switch button 1SB2, the coil of the relay KA3 and the neutral line N; and the two ends of the switch button 1SB2 are also connected in parallel to the normally open contact of the relay KA3.

[0031] Preferably, the local power frequency control circuit specifically includes: the contact 3 of the changeover switch SA2 is connected to the control power supply U21 through the fuse FU5, and the contact 4 of the changeover switch SA2 is connected in sequence to the switch button 2SB1, the switch button 2SB2, the normally closed contact of the overload protection relay KH, the normally closed contact of the contactor KM1, the coil of the contactor KM2 and the neutral line N.

[0032] The two ends of the switch button 2SB2 also include normally open contacts of contactor KM2 connected in parallel. The two ends of the coil of contactor KM2 also include parallel power frequency operation indicator 5XD. One end of the power frequency stop indicator 6XD is connected to fuse FU5 through the normally open contact of contactor KM2, and the other end is connected to the neutral line N. One end of the power frequency overload indicator 7XD is connected to fuse FU5 through the normally open contact of overload protection relay KH, and the other end is connected to the neutral line N.

[0033] It also includes a current measurement circuit and a voltage measurement circuit; the current measurement circuit includes three current transformers and three ammeters; each current transformer is connected in series with an ammeter to form a measurement branch, and the three measurement branches are connected in parallel to measure the current of the three-phase power supply L11, L21, and L31; when the motor is running, the current transformers convert the large current into a small current, which is supplied to the ammeters for measurement and display, thereby realizing the monitoring of the current of the three-phase power supply; the voltage measurement circuit includes a changeover switch SA and a voltmeter; the contact 1 of the changeover switch SA, Contact 3 is connected to the three-phase power supply L11 via fuse FU1. A voltmeter is connected in series between contacts 2 and 4 of the transfer switch SA. Contacts 5 and 7 of the transfer switch SA are connected to the three-phase power supply L21 via fuse FU2. A voltmeter is connected in series between contacts 6 and 8 of the transfer switch SA. Contacts 9 and 11 of the transfer switch SA are connected to the three-phase power supply L31 via fuse FU3. A voltmeter is connected in series between contacts 10 and 12 of the transfer switch SA. The transfer switch SA allows selection of the voltage between different phases. For example, by placing the transfer switch SA in the appropriate position and connecting the voltmeter between the two phases to be measured, the voltmeter can measure and display the voltage value between the two phases, thus enabling monitoring of the three-phase power supply voltage.

[0034] Circuit breakers QF1 and QF2 can quickly cut off the power supply and protect the circuit and equipment when a short circuit or other fault occurs. Overload protection relay KH1 operates when motor M is overloaded, cutting off the coil circuit of contactor KM2 and stopping the motor from operating at the mains frequency. Fuses FU4 and FU5 blow when the circuit current is too high, providing overcurrent protection. The normally closed contact of relay KA4 is connected in series in the circuit of the inverter fault indicator 4XD. When the inverter malfunctions, the KA4 coil is energized, its normally closed contact opens, and the inverter fault indicator 4XD illuminates, displaying the fault information.

[0035] The frequency converter also includes analog input terminals AI1+ and AI1-, and analog output terminals AO1+, AO1- and AO2+ and AO2-. The frequency feedback signal is output from the AO1+ and AO1- terminals, and its output signal is 4-20mA, corresponding to the 0-50Hz motor speed. The current feedback signal is output from the AO2+ and AO2- terminals, and the signal form is also a 4-20mA current signal, which is used to feedback the motor current.

[0036] It also includes the following working principles:

[0037] ① Variable frequency operation mode

[0038] Local frequency conversion operation: Set changeover switch SA1 to the local frequency conversion position and changeover switch SA2 to the frequency conversion position. Close circuit breaker QF1 to energize the main circuit of the frequency converter. The three-phase power supply is input to the frequency converter through the normally open contact of QF1, and then output to motor M through the normally open contact of contactor KM1. Press switch button 1SB2. Current flows through fuse FU4, changeover switches SA1 and SA2, switch buttons 1SB1 and 1SB2, the coil of relay KA3, and neutral line N to form a circuit, energizing the coil of KA3 and closing its normally open contact, thus energizing the coil of time-delay relay KT. After the delay of KT, the normally open contact of KA2 closes, energizing the coil of contactor KM1. The normally open contact of KM1 closes, and motor M is energized and running in frequency conversion mode; at the same time, cooling fan KP1 is energized and the frequency conversion operation indicator 2XD illuminates. Releasing switch button 1SB2 closes the normally open contact of relay KA3, maintaining the energization of the relay KA3 coil and thus keeping the entire circuit operational. During frequency conversion operation, a frequency can be given through the analog input terminals AI1+ and AI1- of the frequency converter according to actual needs. The frequency converter outputs a corresponding frequency voltage signal to drive the motor based on the set frequency and outputs feedback signals such as frequency and current through the analog output terminals AO1+, AO1- and AO2+, AO2- to monitor the motor's operating status.

[0039] Remote frequency conversion operation: Set the selector switch SA1 to the remote frequency conversion position. When a remote start signal is received, current flows through fuse FU4, contacts 1 and 2 of selector switch SA1, the remote start signal, the coil of relay KA2, and the neutral line N to form a circuit, energizing the KA2 coil and closing its normally open contact. This energizes the contactor KM1 coil, closing its normally open contact, starting the motor M and placing it in frequency conversion operation mode. Simultaneously, cooling fan KP1 operates, and the frequency conversion operation indicator 2XD illuminates. If a remote stop signal is received, current flows through contact 2 of selector switch SA1, the remote stop signal, the coil of relay KA1, and the neutral line N to form a circuit, energizing the KA1 coil and opening its normally closed contact. This disconnects the coil circuit of relay KA2, de-energizing the KA2 coil. Its normally open contact resets, de-energizing the contactor KM1 coil and opening its normally open contact, stopping the motor M. Simultaneously, the frequency conversion stop indicator 3XD illuminates.

[0040] ② Power Frequency Operation Mode: With the changeover switch SA2 in the power frequency position, closing circuit breaker QF2 energizes the power frequency bypass circuit. The three-phase power supply is input to the overload protection relay KH1 via the normally open contact of QF2, and then output to motor M. Pressing switch button 2SB2 causes current to flow through fuse FU5, changeover switch SA2, switches 2SB1 and 2SB2, the normally closed contact of overload protection relay KH, the normally closed contact of contactor KM1, the coil of contactor KM2, and the neutral line N, forming a circuit. The KM2 coil is energized, and its normally open contact closes, energizing motor M and placing it in power frequency mode. Simultaneously, the power frequency operation indicator 5XD illuminates. Releasing switch button 2SB2 keeps the KM2 coil energized, maintaining the power frequency operation of motor M. If an overload fault occurs during the operation of motor M at the power frequency, the normally closed contact of the overload protection relay KH will open, cutting off the coil circuit of contactor KM2. The coil of KM2 will be de-energized, its normally open contact will reset, motor M will stop running, and the power frequency overload indicator 7XD will light up.

[0041] When the motor is in standby mode, remotely / locally close the indoor switching power supply, and turn on the circuit breakers for the power supply, control power supply, and fan power supply of the turbine cooler oil pipeline booster pump motor in the local control cabinet. Check for any fault signals to ensure the frequency converter is powered. When starting the motor, first start the motor, check that the operating feedback signal is normal, then set the frequency according to actual needs, and check whether the frequency and current feedback are normal. This utility model realizes the variable frequency operation of the turbine cooler oil pipeline booster pump motor, effectively solving the defects of the existing power frequency operation mode.

[0042] The above description is only a description of the preferred embodiment of the present utility model and is not intended to limit the scope of the present utility model in any way. Any changes or modifications made by those skilled in the art based on the above disclosure shall fall within the protection scope of the claims.

Claims

1. A frequency control device for a turbine oil cooler pipeline booster pump motor, characterized by, It comprises: The variable frequency converter main circuit comprises a circuit breaker QF1, a variable frequency converter and a contactor KM1; three-phase power supply L11, L21 and L31 are connected to the input end R, S and T of the variable frequency converter through the normally open contact of the circuit breaker QF1, and the output end U, V and W of the variable frequency converter are connected to the motor M through the normally open contact of the contactor KM1; The power frequency bypass circuit comprises a circuit breaker QF2, a contactor KM2 and an overload protection relay KH; three-phase power supply L11, L21 and L31 are connected to the input end of the overload protection relay KH through the normally open contact of the circuit breaker QF2, and the output end of the overload protection relay KH is connected to the motor M; The control circuit comprises a remote variable frequency control circuit, an on-site variable frequency control circuit and an on-site power frequency control circuit; the switching of the remote variable frequency control circuit and the on-site variable frequency control circuit is realized through the change-over switch SA1; the switching of the on-site variable frequency control circuit and the on-site power frequency control circuit is realized through the change-over switch SA2.

2. A variable frequency control device for a turbine lube oil cooler piping booster pump motor as claimed in claim 1, wherein, The control circuit further comprises a variable frequency converter main control circuit, which comprises a control power supply U11, a neutral line N, a fuse FU4, relays KA2-KA5, a time delay relay KT, a power supply indicator light 1XD, a cooling fan KP1, a variable frequency operation indicator light 2XD, a variable frequency stop indicator light 3XD and a variable frequency fault indicator light 4XD; one end of the power supply indicator light 1XD is connected to the control power supply U11 through the fuse FU4, and the other end is connected to the neutral line N; the fuse FU4 is connected to the normally closed contact of the contactor KM1, the coil of the contactor KM1 and the neutral line N in sequence through the normally open contact of the relay KA2; the fuse FU4 is connected to the coil of the time delay relay KT and the neutral line N in sequence through the normally open contact of the relay KA3; the outgoing line between the normally open contact of the relay KA2 and the normally open contact of the relay KA3 is connected, the fuse FU4 is connected to the variable frequency stop indicator light 3XD and the neutral line N in sequence through the normally closed contact of the contactor KM1; the fuse FU4 is connected to the cooling fan KP1 and the neutral line N in sequence through the normally open contact of the contactor KM1; the fuse FU4 is connected to the variable frequency operation indicator light 2XD and the neutral line N in sequence through the normally open contact of the relay KA5; the fuse FU4 is connected to the variable frequency fault indicator light 4XD and the neutral line N in sequence through the normally closed contact of the relay KA4.

3. A variable frequency control device for a turbine lube oil cooler piping booster pump motor as claimed in claim 1, wherein, The remote variable frequency control circuit specifically comprises: the contact 1 of the change-over switch SA1 is connected to the control power supply U11 through the fuse FU4, the contact 2 of the change-over switch SA1 is connected to the remote stop signal, the coil of the relay KA1 and the neutral line N in sequence, and the contact 2 of the change-over switch SA1 also bypasses the normally closed contact of the relay KA1, the remote start signal, the coil of the relay KA2 and the neutral line N in sequence, and the two ends of the remote start signal are also connected in parallel with the normally open contact of the relay KA2.

4. A variable frequency control device for a turbine lube oil cooler piping booster pump motor as claimed in claim 1, wherein, The just-in-place frequency conversion control circuit specifically comprises: the contact 3 of the change-over switch SA1 is connected to the control power supply U11 through the fuse FU4, the contact 4 of the change-over switch SA1 is connected to the contact 1 of the change-over switch SA2, the contact 2 of the change-over switch SA2, the switch button 1SB1, the switch button 1SB2, the coil of the relay KA3 and the neutral line N in sequence, and the two ends of the switch button 1SB2 are further connected in parallel with the normally open contact of the relay KA3.

5. A variable frequency control device for a turbine lube oil cooler piping booster pump motor as defined in claim 1 wherein, The just-in-place frequency conversion control circuit specifically comprises: the contact 3 of the change-over switch SA1 is connected to the control power supply U11 through the fuse FU4, the contact 4 of the change-over switch SA1 is connected to the contact 1 of the change-over switch SA2, the contact 2 of the change-over switch SA2, the switch button 1SB1, the switch button 1SB2, the coil of the relay KA3 and the neutral line N in sequence, and the two ends of the switch button 1SB2 are further connected in parallel with the normally open contact of the relay KA3.

6. A variable frequency control device for a turbine lube oil cooler piping booster pump motor as claimed in claim 5 wherein, The two ends of the switch button 2SB2 further comprise the normally open contact of the contactor KM2 connected in parallel, and the two ends of the coil of the contactor KM2 further comprise the frequency operation indicator lamp 5XD connected in parallel; one end of the frequency stop indicator lamp 6XD is connected to the fuse FU5 through the normally open contact of the contactor KM2, and the other end is connected to the neutral line N; one end of the frequency overload indicator lamp 7XD is connected to the fuse FU5 through the normally open contact of the overload protection relay KH, and the other end is connected to the neutral line N.

7. A variable frequency control device for a turbine lube oil cooler piping booster pump motor as claimed in claim 1, wherein Further comprising a current measurement circuit and a voltage measurement circuit; the current measurement circuit comprises three current transformers and three ammeters; each current transformer corresponds to a series-connected ammeter to form a measurement branch, and the three measurement branches are connected in parallel, for measuring the currents of the three-phase power supply L11, L21 and L31; the voltage measurement circuit comprises a change-over switch SA and an voltmeter; the contact 1 and the contact 3 of the change-over switch SA are connected to the three-phase power supply L11 through the fuse FU1, and the contact 2 and the contact 4 of the change-over switch SA are connected in series with the voltmeter; the contact 5 and the contact 7 of the change-over switch SA are connected to the three-phase power supply L21 through the fuse FU2, and the contact 6 and the contact 8 of the change-over switch SA are connected in series with the voltmeter; the contact 9 and the contact 11 of the change-over switch SA are connected to the three-phase power supply L31 through the fuse FU3, and the contact 10 and the contact 12 of the change-over switch SA are connected in series with the voltmeter.

8. A variable frequency control device for a turbine lube oil cooler piping booster pump motor as claimed in any one of claims 1 to 7, characterized in that, The frequency converter further comprises an analog input terminal AI1+, AI1-, an analog output terminal AO1+, AO1- and AO2+, AO2-.

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