Small sewage lifting device control system

Abstract

The utility model provides a small sewage lifting device control system, which is characterized by comprising a circuit breaker, an alternating current contactor, a thermal relay, a fuse, an intermediate relay, a time relay, a safety control transformer, a floating ball, a change-over switch, a button and an indicator lamp, the technical scheme provided by the utility model has the advantages that the sewage lifting pump can be protected against short circuit, overload and the like, and on-site manual and automatic liquid level control, state indication and two-pump alternation can be realized; components and wiring of the control cabinet are simplified, and the cost is saved; the service life of system equipment is prolonged through regular inspection and periodical alternate starting of the water pump, and the energy-saving, safe and practical effects are achieved.

Description

Technical Field

[0001] The utility model relates to the technical field of sewage treatment, in particular to a small sewage lifting device control system. Background Art

[0002] At present, the existing sewage lifting device control equipment has the following defects:

[0003] For sewage lifting pumps with different starting methods, different sewage lifting control cabinets are required to control them due to different wiring of the main circuit of the water pump control, which has poor compatibility; the manufacturing process is complicated and the cost is very high. Summary of the invention

[0004] The utility model aims to provide a small sewage lifting device control system.

[0005] In order to achieve the above purpose, the technical solution of the utility model is:

[0006] A control system for a small sewage lifting device, characterized in that it includes a three-phase five-wire power supply, a first circuit breaker QF11 and a second circuit breaker QF12, the three-phase five-wire power supply is connected to the first circuit breaker QF11 and the second circuit breaker QF12 respectively, the first circuit breaker QF11 and the second circuit breaker QF12 are connected to the main contacts of the first AC contactor KM1 and the second AC contactor KM2 respectively, the outlet ends of the first AC contactor KM1 and the second AC contactor KM2 are connected to the first thermal relay KH1 and the second thermal relay KH2 respectively, the outlet ends of the first thermal relay KH1 and the second thermal relay KH2 are connected to the first sewage pump and the second sewage pump respectively,

[0007] The first circuit breaker QF11 and the second circuit breaker QF12 are connected to the first button SB1 and the third button SB3 respectively through the conversion switch SA, the outlet end of the first button SB1 is connected to the second button SB2 and the first auxiliary normally open contact of the first AC contactor KM1 respectively, and the outlet end of the third button SB3 is connected to the fourth button SB4 and the first auxiliary normally open contact of the second AC contactor KM2 respectively.

[0008] The switching switch SA is also connected to the first normally open contact and the second normally open contact of the second intermediate relay KA2, the first normally open contact and the second normally open contact of the first intermediate relay KA1, and the first normally open contact and the second normally open contact of the seventh intermediate relay KA7.

[0009] The first normally open contact of the second intermediate relay KA2 is connected to the first auxiliary normally closed contact of the second AC contactor KM2, the first auxiliary normally closed contact of the second AC contactor KM2 is respectively connected to the normally closed contact of the fourth intermediate relay KA4 and the second auxiliary normally open contact of the first AC contactor KM1, the second normally open contact of the second intermediate relay KA2 is connected to the first auxiliary normally closed contact of the first AC contactor KM1, the first auxiliary normally closed contact of the first AC contactor KM1 is respectively connected to the first normally open contact of the fourth intermediate relay KA4 and the second auxiliary normally open contact of the second AC contactor KM2,

[0010] The second button SB2, the first auxiliary normally open contact of the first AC contactor KM1, the normally closed contact of the fourth intermediate relay KA4, the second auxiliary normally open contact of the first AC contactor KM1, the first normally open contact of the first intermediate relay KA1 and the first normally open contact of the seventh intermediate relay KA7 are merged and respectively connected to the coil of the first AC contactor KM1 and the fourth indicator light HL4. The coil of the first AC contactor KM1 and the fourth indicator light HL4 are merged and connected to the first normally closed contact of the fifth intermediate relay KA5. The fifth intermediate relay KA5 is connected to the center line N.

[0011] The fourth button SB4, the first auxiliary normally open contact of the second AC contactor KM2, the normally open contact of the fourth intermediate relay KA4, the second auxiliary normally open contact of the second AC contactor KM2, the second normally open contact of the first intermediate relay KA1 and the second normally open contact of the seventh intermediate relay KA7 are merged and respectively connected to the coil of the second AC contactor KM2 and the fifth indicator light HL5. The coil of the second AC contactor KM2 and the fifth indicator light HL5 are merged and connected to the first normally closed contact of the sixth intermediate relay KA6. The sixth intermediate relay KA6 is connected to the center line N.

[0012] The three-phase five-wire power supply is also connected to the fuse FU, and the outlet end of the fuse FU is respectively connected to the normally open contact of the fifth intermediate relay KA5, the third auxiliary normally open contact of the first AC contactor KM1, and the second normally open contact of the fourth intermediate relay KA4. The fifth intermediate relay KA5, the first AC contactor KM1, and the fourth intermediate relay KA4 are connected to the second auxiliary normally closed contact of the second AC contactor KM2 after merging. The second AC contactor KM2 is connected to the second normally closed contact of the sixth intermediate relay KA6. The sixth intermediate relay KA6 is connected to the coil of the fourth intermediate relay KA4. The coil of the fourth intermediate relay KA4 is connected to the center line N.

[0013] Furthermore, the fuse FU is connected to one end of the primary of the safety control transformer T, the other end of the primary of the safety control transformer T is connected to the center line N, and one end of the secondary of the safety control transformer T is respectively connected to the first float SL1, the second float SL2, the third float SL3, the third normally open contact of the first intermediate relay KA1 and the third normally open contact of the second intermediate relay KA2, the first float SL1 and the third normally open contact of the first intermediate relay KA1 are connected to the first normally open contact of the third intermediate relay KA3 after merging, and the first normally open contact of the third intermediate relay KA3 is connected to the first normally open contact of the third intermediate relay KA3. The coil of the first intermediate relay KA1 is connected to the other end of the secondary pole of the safety control transformer T, the second float SL2 and the third normally open contact of the second intermediate relay KA2 are merged and connected to the second normally open contact of the third intermediate relay KA3, the second normally open contact of the third intermediate relay KA3 is connected to the coil of the second intermediate relay KA2, the third float SL3 is connected to the coil of the third intermediate relay KA3, the coils of the first intermediate relay KA1, the second intermediate relay KA2 and the third intermediate relay K3 are all connected to the other end of the secondary pole of the safety control transformer T.

[0014] Furthermore, the fuse FU is connected to a first indicator light HL1 , and the first indicator light HL1 is connected to a center line N.

[0015] Furthermore, the fuse FU is respectively connected to the first thermal relay KH1 and the second thermal relay KH2, the output end of the first thermal relay KH1 is respectively connected to the coil of the fifth intermediate relay KA5 and the second indicator light HL2, the coil of the fifth intermediate relay KA5 and the second indicator light HL2 are connected to the center line N after merging, the second thermal relay KH2 is respectively connected to the coil of the sixth intermediate relay KA6 and the third indicator light HL3, the coil of the sixth intermediate relay KA6 and the third indicator light HL3 are connected to the center line N after merging.

[0016] Furthermore, the fuse FU is connected to the switching switch SA, the switching switch SA is connected to the third auxiliary normally closed contact of the second AC contactor KM2, the third auxiliary normally closed contact of the second AC contactor KM2 is connected to the third auxiliary normally closed contact of the first AC contactor KM1, the third auxiliary normally closed contact of the first AC contactor KM1 is connected to the coil of the first time relay KT1, and the coil of the first time relay KT1 is connected to the center line N.

[0017] Further, the fuse FU is respectively connected to the normally open contact of the first time relay KT1 and the normally open contact of the seventh intermediate relay KA7, the normally open contact of the first time relay KT1 and the normally open contact of the seventh intermediate relay KA7 are merged and connected to the normally closed contact of the second time relay KT2, the normally closed contact of the second time relay KT2 is connected to the normally closed contact of the second intermediate relay KA2, the normally closed contact of the second intermediate relay KA2 is respectively connected to the coil of the seventh intermediate relay KA7, the coil of the second time relay KT2 and the sixth indicator light HL6, the coil of the seventh intermediate relay KA7, the coil of the second time relay KT2 and the sixth indicator light HL6 are merged and connected to the center line N.

[0018] The utility model completes the short-circuit protection function of the main circuit and the control circuit of the sewage pump through the combination of the circuit breaker and the fuse, and performs overload protection on the sewage pump through the thermal relay to avoid damage to the sewage pump motor due to excessive current;

[0019] The utility model can carry out two-pump rotation, balances the use frequency of the sewage pump, prolongs the service life of the equipment, and reduces the failure rate of a single sewage pump. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 The electrical schematic diagram of the manual control and automatic control of the utility model;

[0021] Figure 2 This is the electrical schematic diagram of the utility model for two-pump rotation, fault detection, regular inspection and liquid level detection.

[0022] Reference numerals:

[0023] QF11, QF12 first and second circuit breakers, FU fuses,

[0024] KM1, KM2 first and second AC contactors,

[0025] KH1, KH2 first and second thermal relays,

[0026] KA1~KA6 first~sixth intermediate relay,

[0027] KT1~KT2 first and second time relays,

[0028] HL1~HL6 first~sixth indicator light,

[0029] SA switch,

[0030] SB1~SB4 first~fourth button,

[0031] T safety control transformer,

[0032] SL1~SL3 first~third floats. DETAILED DESCRIPTION

[0033] The technical solution of the utility model will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments of the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.

[0034] The utility model discloses a small sewage lifting device control system. Figure 1 As shown, it includes a three-phase five-wire power supply AC380V / 50Hz, a first circuit breaker QF11 and a second circuit breaker QF12. The three-phase five-wire power supply is respectively connected to the first circuit breaker QF11 and the second circuit breaker QF12. The first circuit breaker QF11 and the second circuit breaker QF12 are respectively connected to the main contacts of the first AC contactor KM1 and the second AC contactor KM2. The outlet ends of the first AC contactor KM1 and the second AC contactor KM2 are respectively connected to the first thermal relay KH1 and the second thermal relay KH2. The outlet ends of the first thermal relay KH1 and the second thermal relay KH2 are respectively connected to the first sewage pump and the second sewage pump.

[0035] The first circuit breaker QF11 and the second circuit breaker QF12 are connected to the first button SB1 and the third button SB3 respectively through the conversion switch SA, the output end of the first button SB1 is connected to the second button SB2 and the first auxiliary normally open contact of the first AC contactor KM1 respectively, and the output end of the third button SB3 is connected to the fourth button SB4 and the first auxiliary normally open contact of the second AC contactor KM2 respectively.

[0036] The change-over switch SA is also connected to the first normally open contact and the second normally open contact of the second intermediate relay KA2, the first normally open contact and the second normally open contact of the first intermediate relay KA1, and the first normally open contact and the second normally open contact of the seventh intermediate relay KA7, respectively.

[0037] The first normally open contact of the second intermediate relay KA2 is connected to the first auxiliary normally closed contact of the second AC contactor KM2, the first auxiliary normally closed contact of the second AC contactor KM2 is respectively connected to the normally closed contact of the fourth intermediate relay KA4 and the second auxiliary normally open contact of the first AC contactor KM1, the second normally open contact of the second intermediate relay KA2 is connected to the first auxiliary normally closed contact of the first AC contactor KM1, and the first auxiliary normally closed contact of the first AC contactor KM1 is respectively connected to the first normally open contact of the fourth intermediate relay KA4 and the second auxiliary normally open contact of the second AC contactor KM2.

[0038] like Figure 1As shown, the second button SB2, the first auxiliary normally open contact of the first AC contactor KM1, the normally closed contact of the fourth intermediate relay KA4, the second auxiliary normally open contact of the first AC contactor KM1, the first normally open contact of the first intermediate relay KA1 and the first normally open contact of the seventh intermediate relay KA7 are converged and respectively connected to the coil of the first AC contactor KM1 and the fourth indicator light HL4; the coil of the first AC contactor KM1 and the fourth indicator light HL4 are converged and connected to the first normally closed contact of the fifth intermediate relay KA5; and the fifth intermediate relay KA5 is connected to the center line N.

[0039] The fourth button SB4, the first auxiliary normally open contact of the second AC contactor KM2, the normally open contact of the fourth intermediate relay KA4, the second auxiliary normally open contact of the second AC contactor KM2, the second normally open contact of the first intermediate relay KA1 and the second normally open contact of the seventh intermediate relay KA7 are converged and respectively connected to the coil of the second AC contactor KM2 and the fifth indicator light HL5. The coil of the second AC contactor KM2 and the fifth indicator light HL5 are converged and connected to the first normally closed contact of the sixth intermediate relay KA6. The sixth intermediate relay KA6 is connected to the center line N.

[0040] The manual / stop / automatic operation is controlled by the conversion switch SA, the first sewage pump is manually controlled by the first button SB1 and the second button SB2, the second sewage pump is manually controlled by the third button SB3 and the fourth button SB4, the combination of the first AC contactor KM1, the second AC contactor KM2, the first intermediate relay KA2, the second intermediate relay KA2 and the fourth intermediate relay KA4 completes the automatic control of the first sewage pump and the second sewage pump, and the seventh intermediate relay KA7 controls the inspection of the first sewage pump and the second sewage pump.

[0041] The three-phase five-wire power supply is also connected to the fuse FU, such as Figure 2 As shown, the output terminal of the fuse FU is respectively connected to the normally open contact of the fifth intermediate relay KA5, the third auxiliary normally open contact of the first AC contactor KM1, and the second normally open contact of the fourth intermediate relay KA4; the fifth intermediate relay KA5, the first AC contactor KM1 and the fourth intermediate relay KA4 are connected to the second auxiliary normally closed contact of the second AC contactor KM2 after being combined; the second AC contactor KM2 is connected to the second normally closed contact of the sixth intermediate relay KA6; the sixth intermediate relay KA6 is connected to the coil of the fourth intermediate relay KA4; and the coil of the fourth intermediate relay KA4 is connected to the center line N.

[0042] The rotation of the first sewage pump and the second sewage pump is completed by the normally open contact of the fifth intermediate relay KA5, the third auxiliary normally open contact of the first AC contactor KM1, the second normally open contact of the fourth intermediate relay KA4, the second auxiliary normally closed contact of the second AC contactor KM2 and the second normally closed contact of the sixth intermediate relay KA6.

[0043] The fuse FU is connected to the first indicator light HL1 , the first indicator light HL1 is connected to the center line N, and the first indicator light HL1 is used as a power indicator light.

[0044] The fuse FU is connected to the first thermal relay KH1 and the second thermal relay KH2 respectively. The output terminals of the first thermal relay KH1 are connected to the coil of the fifth intermediate relay KA5 and the second indicator light HL2 respectively. The coil of the fifth intermediate relay KA5 and the second indicator light HL2 are connected to the center line N after merging. When the first sewage pump fails, the normally open contact of the first thermal relay KH1 is closed and the second indicator light HL2 lights up.

[0045] The second thermal relay KH2 is connected to the coil of the sixth intermediate relay KA6 and the third indicator light HL3 respectively. The coil of the sixth intermediate relay KA6 and the third indicator light HL3 are connected to the center line N after merging. When the second sewage pump fails, the normally open contact of the second thermal relay KH2 is closed and the third indicator light HL3 lights up.

[0046] like Figure 2 As shown, the fuse FU is connected to the transfer switch SA, the transfer switch SA is connected to the third auxiliary normally closed contact of the second AC contactor KM2, the third auxiliary normally closed contact of the second AC contactor KM2 is connected to the third auxiliary normally closed contact of the first AC contactor KM1, the third auxiliary normally closed contact of the first AC contactor KM1 is connected to the coil of the first time relay KT1, and the coil of the first time relay KT1 is connected to the center line N.

[0047] The fuse FU is respectively connected to the normally open contact of the first time relay KT1 and the normally open contact of the seventh intermediate relay KA7, the normally open contact of the first time relay KT1 and the normally open contact of the seventh intermediate relay KA7 are merged and connected to the normally closed contact of the second time relay KT2, the normally closed contact of the second time relay KT2 is connected to the normally closed contact of the second intermediate relay KA2, the normally closed contact of the second intermediate relay KA2 is respectively connected to the coil of the seventh intermediate relay KA7, the coil of the second time relay KT2 and the sixth indicator light HL6, the coil of the seventh intermediate relay KA7, the coil of the second time relay KT2 and the sixth indicator light HL6 are merged and connected to the center line N.

[0048] According to the set time of the first time relay KT1 and the second time relay KT2, automatic inspection is performed, and the sixth indicator light HL6 lights up when the inspection starts.

[0049] Fuse FU is connected to one end of the primary of safety control transformer T, the other end of the primary of safety control transformer T is connected to the center line N, safety control transformer T is a 220V / 36V transformer, and one end of the secondary of safety control transformer T is respectively connected to the first float SL1, the second float SL2, the third float SL3, the third normally open contact of the first intermediate relay KA1 and the third normally open contact of the second intermediate relay KA2.

[0050] The first float SL1 and the third normally open contact of the first intermediate relay KA1 are connected to the first normally open contact of the third intermediate relay KA3, the first normally open contact of the third intermediate relay KA3 is connected to the coil of the first intermediate relay KA1, and to the other end of the secondary pole of the safety control transformer T, the second float SL2 and the third normally open contact of the second intermediate relay KA2 are connected to the second normally open contact of the third intermediate relay KA3, the second normally open contact of the third intermediate relay KA3 is connected to the coil of the second intermediate relay KA2, the third float SL3 is connected to the coil of the third intermediate relay KA3, the coils of the first intermediate relay KA1, the second intermediate relay KA2 and the third intermediate relay K3 are all connected to the other end of the secondary pole of the safety control transformer T.

[0051] When the utility model is put into use, the first circuit breaker QF11 and the second circuit breaker QF12 are first closed, the fuse FU works normally, the parameters of each thermal relay and time relay are set, and the system is in a power-on standby state;

[0052] Select manual / automatic state by switching switch SA to realize manual control or automatic control of the system;

[0053] If the system is in manual mode, the first sewage pump is started by the first button SB1, the first sewage pump can be manually stopped by the second button SB2, the second sewage pump is started by the third button SB3, and the second sewage pump can be manually stopped by the fourth button SB4.

[0054] If the system is in automatic state, the inspection function is started according to the set inspection cycle, and the first sewage pump and the second sewage pump are inspected regularly, and the start and stop of the first sewage pump and the second sewage pump are controlled according to the liquid level feedback of the first float SL1, the second float SL2, and the third float SL3.

[0055] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the utility model, rather than to limit it. Although the utility model has been described in detail with reference to the aforementioned embodiments, ordinary technicians in this field should understand that they can still modify the technical solutions recorded in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not make the essence of the corresponding technical solution deviate from the scope of the technical solution of the embodiments of the utility model.

Claims

1. A small sewage lifting device control system, characterized in that: It includes a three-phase five-wire power supply, a first circuit breaker QF11 and a second circuit breaker QF12, the three-phase five-wire power supply is connected to the first circuit breaker QF11 and the second circuit breaker QF12 respectively, the first circuit breaker QF11 and the second circuit breaker QF12 are connected to the main contacts of the first AC contactor KM1 and the second AC contactor KM2 respectively, the outlet ends of the first AC contactor KM1 and the second AC contactor KM2 are connected to the first thermal relay KH1 and the second thermal relay KH2 respectively, the outlet ends of the first thermal relay KH1 and the second thermal relay KH2 are connected to the first sewage pump and the second sewage pump respectively, The first circuit breaker QF11 and the second circuit breaker QF12 are connected to the first button SB1 and the third button SB3 respectively through the conversion switch SA, the outlet end of the first button SB1 is connected to the second button SB2 and the first auxiliary normally open contact of the first AC contactor KM1 respectively, and the outlet end of the third button SB3 is connected to the fourth button SB4 and the first auxiliary normally open contact of the second AC contactor KM2 respectively. The switching switch SA is also connected to the first normally open contact and the second normally open contact of the second intermediate relay KA2, the first normally open contact and the second normally open contact of the first intermediate relay KA1, and the first normally open contact and the second normally open contact of the seventh intermediate relay KA7. The first normally open contact of the second intermediate relay KA2 is connected to the first auxiliary normally closed contact of the second AC contactor KM2, the first auxiliary normally closed contact of the second AC contactor KM2 is respectively connected to the normally closed contact of the fourth intermediate relay KA4 and the second auxiliary normally open contact of the first AC contactor KM1, the second normally open contact of the second intermediate relay KA2 is connected to the first auxiliary normally closed contact of the first AC contactor KM1, the first auxiliary normally closed contact of the first AC contactor KM1 is respectively connected to the first normally open contact of the fourth intermediate relay KA4 and the second auxiliary normally open contact of the second AC contactor KM2, The second button SB2, the first auxiliary normally open contact of the first AC contactor KM1, the normally closed contact of the fourth intermediate relay KA4, the second auxiliary normally open contact of the first AC contactor KM1, the first normally open contact of the first intermediate relay KA1 and the first normally open contact of the seventh intermediate relay KA7 are merged and respectively connected to the coil of the first AC contactor KM1 and the fourth indicator light HL4. The coil of the first AC contactor KM1 and the fourth indicator light HL4 are merged and connected to the first normally closed contact of the fifth intermediate relay KA5. The fifth intermediate relay KA5 is connected to the center line N. The fourth button SB4, the first auxiliary normally open contact of the second AC contactor KM2, the normally open contact of the fourth intermediate relay KA4, the second auxiliary normally open contact of the second AC contactor KM2, the second normally open contact of the first intermediate relay KA1 and the second normally open contact of the seventh intermediate relay KA7 are merged and respectively connected to the coil of the second AC contactor KM2 and the fifth indicator light HL5. The coil of the second AC contactor KM2 and the fifth indicator light HL5 are merged and connected to the first normally closed contact of the sixth intermediate relay KA6. The sixth intermediate relay KA6 is connected to the center line N. The three-phase five-wire power supply is also connected to the fuse FU, and the outlet end of the fuse FU is respectively connected to the normally open contact of the fifth intermediate relay KA5, the third auxiliary normally open contact of the first AC contactor KM1, and the second normally open contact of the fourth intermediate relay KA4. The fifth intermediate relay KA5, the first AC contactor KM1, and the fourth intermediate relay KA4 are connected to the second auxiliary normally closed contact of the second AC contactor KM2 after merging. The second AC contactor KM2 is connected to the second normally closed contact of the sixth intermediate relay KA6. The sixth intermediate relay KA6 is connected to the coil of the fourth intermediate relay KA4. The coil of the fourth intermediate relay KA4 is connected to the center line N. The fuse FU is connected to one end of the primary of the safety control transformer T, and the other end of the primary of the safety control transformer T is connected to the center line N. One end of the secondary of the safety control transformer T is respectively connected to the first float SL1, the second float SL2, the third float SL3, the third normally open contact of the first intermediate relay KA1 and the third normally open contact of the second intermediate relay KA2. The first float SL1 and the third normally open contact of the first intermediate relay KA1 are connected to the first normally open contact of the third intermediate relay KA3 after merging. The first normally open contact of the third intermediate relay KA3 is connected to the coil of the first intermediate relay KA1 and to the other end of the secondary of the safety control transformer T. The second float SL2 and the third normally open contact of the second intermediate relay KA2 are connected to the second normally open contact of the third intermediate relay KA3 after merging. The second normally open contact of the third intermediate relay KA3 is connected to the coil of the second intermediate relay KA2. The third float SL3 is connected to the coil of the third intermediate relay KA3. The coils of the first intermediate relay KA1, the second intermediate relay KA2 and the third intermediate relay K3 are all connected to the other end of the secondary of the safety control transformer T.

2. The small sewage lifting device control system according to claim 1 is characterized in that: The fuse FU is connected to the first indicator light HL1 , and the first indicator light HL1 is connected to the center line N.

3. The small sewage lifting device control system according to claim 1 is characterized in that: The fuse FU is connected to the first thermal relay KH1 and the second thermal relay KH2 respectively, the output end of the first thermal relay KH1 is connected to the coil of the fifth intermediate relay KA5 and the second indicator light HL2 respectively, the coil of the fifth intermediate relay KA5 and the second indicator light HL2 are connected to the center line N after merging, the second thermal relay KH2 is connected to the coil of the sixth intermediate relay KA6 and the third indicator light HL3 respectively, the coil of the sixth intermediate relay KA6 and the third indicator light HL3 are connected to the center line N after merging.

4. The small sewage lifting device control system according to claim 1 is characterized in that: The fuse FU is connected to the conversion switch SA, the conversion switch SA is connected to the third auxiliary normally closed contact of the second AC contactor KM2, the third auxiliary normally closed contact of the second AC contactor KM2 is connected to the third auxiliary normally closed contact of the first AC contactor KM1, the third auxiliary normally closed contact of the first AC contactor KM1 is connected to the coil of the first time relay KT1, and the coil of the first time relay KT1 is connected to the center line N.

5. The small sewage lifting device control system according to claim 4 is characterized in that: The fuse FU is respectively connected to the normally open contact of the first time relay KT1 and the normally open contact of the seventh intermediate relay KA7, the normally open contact of the first time relay KT1 and the normally open contact of the seventh intermediate relay KA7 are merged and connected to the normally closed contact of the second time relay KT2, the normally closed contact of the second time relay KT2 is connected to the normally closed contact of the second intermediate relay KA2, the normally closed contact of the second intermediate relay KA2 is respectively connected to the coil of the seventh intermediate relay KA7, the coil of the second time relay KT2 and the sixth indicator light HL6, the coil of the seventh intermediate relay KA7, the coil of the second time relay KT2 and the sixth indicator light HL6 are merged and connected to the center line N.

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