Eddy current dynamometer and its protection circuit

Abstract

The present invention relates to an eddy current dynamometer and its protection circuit, including a single-chip computer mainboard, an eddy current machine protection board, an eddy current machine loading circuit, and a lifter electromagnetic valve. The single-chip computer mainboard includes a single-chip computer control system for receiving and processing vehicle positioning signals, and a raising relay and a lowering relay for outputting vehicle positioning signals; the eddy current machine protection board includes a first relay, a second relay, a normally closed switch, and a normally open switch; the first relay and the second relay are respectively connected to the lifter electromagnetic valve; the eddy current machine loading circuit includes an AC contactor and an excitation coil, the AC contactor includes a contact coil and a contact switch, the excitation coil is installed on the eddy current machine stator and connected to the eddy current machine loading circuit; the raising relay is connected to the first relay, the lowering relay is connected to the second relay, the AC contactor is powered on and off according to the on-off state of the raising relay and the lowering relay, and it is ensured that the excitation coil can be loaded with voltage only when the vehicle drives onto the platform for detection.

Description

Technical Field

[0001] The invention relates to the field of eddy current chassis dynamometers, and more specifically to an eddy current dynamometer and a protection circuit thereof. Background Art

[0002] The automobile chassis dynamometer in the related art, as a bench test equipment for simulating the actual resistance of a vehicle on the road, generally uses an eddy current machine as a power absorption device to load the roller. The eddy current machine consists of two parts: a stator and a rotor. The stator part includes an excitation coil L1 mounted on it. By adjusting the on-off time of the excitation current to the excitation coil L1, different braking torques T (N·m) can be obtained. When the dynamometer roller rotates at a speed of n (r / min), a resistance load P = T·n / 9549 equivalent to the actual vehicle on the road can be obtained.

[0003] like Figure 5 The circuit protection measures for the excitation coil L1 generally include a fast-fuse fuse and an emergency switch E1. The 220V AC power supply is rectified by the rectifier bridge BRIDGE1, and then inverted by the power semiconductor device IGBT to provide excitation current to the excitation coil L1 of the eddy current machine. Since the braking torque varies greatly with different test conditions, the fast-fuse fuse F1 can only be configured with the maximum current. In practical applications, when the power semiconductor device IGBT that controls the on-off time of the excitation current breaks down and short-circuits due to overvoltage or overheating, and the fuse current of F1 is not reached at this time, the excitation coil L1 may overheat and burn due to long-term power-on. In addition, the emergency switch E1 is directly connected in series to the main power supply circuit, and the contacts are often burned out. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide an eddy current dynamometer and a protection circuit thereof.

[0005] The technical solution adopted by the present invention to solve the technical problem is: constructing a protection circuit of an eddy current dynamometer, including a single-chip computer mainboard, an eddy current machine protection board, an eddy current machine loading circuit, and a lifter electromagnetic valve;

[0006] The single-chip computer mainboard includes a single-chip computer control system for receiving and processing a vehicle positioning signal, and a rising relay and a falling relay for outputting the vehicle positioning signal;

[0007] The eddy current machine protection board includes a first relay, a second relay, a normally closed switch connected to the first relay, and a normally open switch connected to the second relay;

[0008] The first relay and the second relay are electrically connected to the lifter solenoid valve respectively to send signals to the lifter solenoid valve respectively;

[0009] The eddy current machine loading circuit includes an AC contactor and an excitation coil which are electrically connected. The AC contactor includes a contact coil and a contact switch. The excitation coil is installed on the stator of the eddy current machine and is communicatively connected with the eddy current machine loading circuit.

[0010] The normally closed switch, the normally open switch, and the contact coil are connected in sequence, and the normally open switch and the contact switch are connected in parallel;

[0011] The up relay is connected to the first relay, the down relay is connected to the second relay, and the AC contactor is energized or de-energized according to the on / off states of the up relay and the down relay.

[0012] Preferably, the eddy current machine protection plate is connected to an emergency switch for controlling the AC contactor.

[0013] Preferably, the eddy current machine loading circuit further includes a power semiconductor device IGBT connected to the excitation coil.

[0014] Preferably, the protection circuit also includes an electrically connected fast-blow fuse and a rectifier bridge. The current is converted into pulsating direct current by the rectifier bridge and then inverted by the power semiconductor device IGBT to provide excitation current to the excitation coil. The fast-blow fuse is configured with rated current.

[0015] Preferably, the protection circuit also includes an eddy current machine driving board connected between the single-chip computer mainboard and the eddy current machine loading circuit, so that the single-chip computer mainboard outputs a driving signal to the eddy current machine driving board; and controls the on and off of the eddy current machine loading circuit according to the driving signal received by the eddy current machine driving board.

[0016] Preferably, the eddy current machine driving board includes electrically connected current limiting resistors R2, R4, a driving module TLP250, and a driving resistor R1, the current limiting resistors R2 and R4 are connected to the single-chip computer mainboard, and the driving resistor R1 is connected to the power semiconductor device IGBT.

[0017] Preferably, the PWM signal output by the single-chip computer mainboard is connected to the positive pole 2 and the negative pole 3 of the driving module TLP250 respectively through the current limiting resistor R2 and the current limiting resistor R4, and is output as a voltage signal from the pins 6 and 7 of the driving module TLP250 after voltage and power amplification by the driving module TLP250, and is connected to the control electrode G of the power semiconductor device IGBT through the driving resistor R1, so that the conduction time of the power semiconductor device IGBT changes with the duty cycle of the PWM signal, and the current passing through the excitation coil also changes, thereby changing the drum speed.

[0018] An eddy current dynamometer comprises a protection circuit of the eddy current dynamometer. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The present invention will be further described below with reference to the accompanying drawings and embodiments, in which:

[0020] Figure 1 It is a schematic diagram of the principle of the protection circuit of the eddy current dynamometer in the embodiment of the present invention.

[0021] Figure 2 yes Figure 1 Schematic diagram of the connection between the main single-chip control system and the up relay and down relay.

[0022] Figure 3 yes Figure 1 Schematic diagram of the connection circuit between the first relay, the second relay of the China Electric eddy current machine protection board and the lifter solenoid valve and AC contactor.

[0023] Figure 4 It is a schematic diagram of the connection circuit between a fast-blow fuse, a rectifier bridge, an eddy current machine drive board, an eddy current machine loading circuit, and an excitation coil.

[0024] Figure 5 It is a schematic diagram of an eddy current machine excitation coil protection circuit in the background technology. DETAILED DESCRIPTION

[0025] In order to have a clearer understanding of the technical features, purposes and effects of the present invention, specific embodiments of the present invention are now described in detail with reference to the accompanying drawings.

[0026] like Figures 1 to 3 As shown, an eddy current dynamometer in a preferred embodiment of the present invention includes a single chip computer mainboard, an eddy current machine protection board, an eddy current machine loading circuit, and a lifter solenoid valve.

[0027] The single-chip microcomputer mainboard comprises a single-chip microcomputer control system for receiving and processing vehicle positioning signals, and an up relay and a down relay for outputting the vehicle positioning signals.

[0028] The eddy current machine protection board includes a first relay Z1, a second relay Z2, a normally closed switch Z3 connected to the first relay Z1, and a normally open switch Z4 connected to the second relay Z2. The first relay Z1 and the second relay Z2 are electrically connected to the lifter solenoid valve respectively to send signals to the lifter solenoid valve respectively.

[0029] Combination Figure 3 As shown, the eddy current machine loading circuit includes an electrically connected AC contactor K and an excitation coil L. The AC contactor K includes a contact coil K1 and a contact switch K2. The excitation coil L is installed on the stator of the eddy current machine and is communicatively connected to the eddy current machine loading circuit.

[0030] The normally closed switch Z3, the normally open switch Z4, and the contact coil K1 are connected in sequence, the normally closed switch Z3 remains in a normally closed state, the normally open switch Z4 remains in a normally open state, and the normally open switch Z4 and the contact switch K2 are connected in parallel.

[0031] The raising relay is connected to the first relay Z1, and the lowering relay is connected to the second relay Z2. The AC contactor K is energized or de-energized according to the on / off states of the raising relay and the lowering relay.

[0032] When the test vehicle drives onto the dynamometer body, the single-chip microcomputer mainboard will receive the vehicle positioning signal and output a CPU pulse signal to close the step-down relay on the single-chip microcomputer mainboard. At the same time, the second relay Z2 on the protection board is closed. After the contact coil K1 of the AC contactor K is energized, the contact switch K2 is also closed at the same time, and the DC voltage U+ is added to the excitation coil L after passing through the AC contactor K.

[0033] When the output pulse signal stops, the AC contactor K is self-locked through the contact switch K2, and the excitation coil L is always loaded with voltage U+.

[0034] After the vehicle inspection is completed, the CPU outputs a pulse signal to close the boost relay on the single-chip mainboard, and the first relay Z1 on the protection board is closed at the same time. The contact coil K1 of the AC contactor K is disconnected due to the disconnection of the normally closed switch Z3, and the excitation coil L is disconnected due to the disconnection of the contact switch K2 of the AC contactor K. This ensures that the excitation coil L can only be loaded with voltage when the vehicle is driven onto the platform for inspection, and no voltage is loaded after the vehicle leaves the platform, and the excitation coil L will not be burned when the vehicle is not inspected.

[0035] The eddy current machine protection board is connected to an emergency switch E for controlling the AC contactor K. The function of the emergency switch E is to cancel the eddy current machine loading voltage when the vehicle deviates out of control.

[0036] The eddy current machine loading circuit also includes a power semiconductor device IGBT connected to the excitation coil L. Since the excitation coil L can only be loaded with voltage when the vehicle is driven onto the platform for detection, and no voltage is loaded after the vehicle leaves the platform, even if the power semiconductor device IGBT breaks down and short-circuits, the excitation coil L will not be burned when the vehicle is not tested. Once the vehicle has difficulty starting due to the large loading force at the beginning of the test, the power semiconductor device IGBT can be found to be short-circuited immediately, thereby cutting off the main power supply and protecting the eddy current machine.

[0037] Combination Figure 4As shown, the protection circuit also includes an electrically connected fast-blow fuse F and a rectifier bridge B. The current is converted into pulsating direct current by the rectifier bridge B, and then inverted by the power semiconductor device IGBT to provide excitation current to the excitation coil L. Since the circuit is relatively safe, the fast-blow fuse F can be configured with the rated current, that is, the maximum current configuration of the circuit, and there will be no overheating and burning.

[0038] When the power semiconductor device IGBT of the eddy current machine fails due to overcurrent, overvoltage and overheating during the detection process, and manifests as a direct short circuit of the power semiconductor device IGBT, the current on the excitation coil L will be very large without a control signal.

[0039] Since the braking torque varies greatly with different test conditions, and the fast-acting fuse F can only be configured with the maximum current, this large current is often not enough to cause the fast-acting fuse F to melt; if the eddy current machine is not started to do work at this time, the current will output work in the form of heat, which will cause the excitation coil L of the eddy current machine to overheat and burn out over time.

[0040] Furthermore, a freewheeling tube D connected in parallel with the excitation coil L can prevent sudden changes in the current of the excitation coil L. In addition, a filter capacitor C connected in parallel with the rectifier bridge B can also prevent sudden changes in the current in the circuit.

[0041] An eddy current machine protection circuit is added, and the first relay Z1 normally closed and the second relay Z2 normally open signals are added so that the excitation coil L can work. Even if the power semiconductor device IGBT is short-circuited, as long as the AC contactor K is not closed, the DC voltage will not be added to the excitation coil L, thereby achieving protection for the excitation coil L.

[0042] Another advantage of the above improved circuit is that it can promptly detect whether the power semiconductor device IGBT is damaged. When the power semiconductor device IGBT is in a short-circuit state, the current on the excitation coil L will be very large without being controlled by the signal, causing difficulty in starting the vehicle. The guide or operator can know whether the power semiconductor device IGBT is damaged by observing the ammeter, thereby cutting off the emergency switch E in time to protect the excitation coil L.

[0043] If there is no eddy current machine protection board, the 220V voltage when the lift is rising and falling will be directly loaded on the microcontroller motherboard. The electric sparks generated by the closing and releasing of the relay will affect the CPU on the motherboard, causing the CPU program to run away and crash.

[0044] If there is no eddy current machine protection board, the small relay directly driven by the single-chip computer mainboard controls the rise and fall of the lifter and the on and off of the eddy current machine loading main circuit. The 220V voltage's attraction and release will damage the contacts on the small relay, often causing the single-chip computer mainboard to short-circuit and burn.

[0045] If there is no eddy current machine protection board, the emergency switch E is directly connected to the eddy current machine loading main circuit. Due to the large current, it is also easy to cause the contacts of the emergency switch E to burn out. By controlling the AC contactor K through the emergency switch E to control the opening / closing of the eddy current machine loading main circuit, the current is very small and will not burn out the contacts.

[0046] The protection circuit also includes an eddy current machine driving board connected between the single-chip computer mainboard and the eddy current machine loading circuit, so that the single-chip computer mainboard outputs a driving signal to the eddy current machine driving board; and controls the on and off of the eddy current machine loading circuit according to the driving signal received by the eddy current machine driving board.

[0047] The eddy current machine driving board includes electrically connected current limiting resistors R2, R4, a driving module TLP250, and a driving resistor R1. The current limiting resistors R2 and R4 are connected to the single-chip computer mainboard, and the driving resistor R1 is connected to the power semiconductor device IGBT.

[0048] The set detection speed is transmitted to the single-chip microcomputer mainboard through the communication module by the industrial control computer control system. The single-chip microcomputer mainboard uses a correction algorithm to output a PWM (pulse width modulation signal) signal with adjustable duty cycle based on the characteristics of the eddy current dynamometer and the actual vehicle speed signal, so that the error between the actual detection speed and the set detection speed is controlled within ±0.5km / h.

[0049] The PWM signal output by the single-chip computer mainboard is connected to the positive pin 2 and the negative pin 3 of the driving module TLP250 through the current limiting resistor R2 and the current limiting resistor R4 respectively, and is output as a voltage signal from the pin 6 and the pin 7 of the driving module TLP250 after the voltage and power amplification of the driving module TLP250, and is connected to the control electrode G of the power semiconductor device IGBT through the driving resistor R1, so that the conduction time of the power semiconductor device IGBT changes with the duty cycle of the PWM signal, and the current through the excitation coil L also changes, thereby achieving the purpose of changing the drum speed.

[0050] The PWM duty cycle controls the on and off time of the power semiconductor device IGBT, which is reflected in the voltage on the eddy current machine excitation coil L. The higher the voltage, the greater the force on the drum, and the drum reduces its speed. On the contrary, the drum speed increases. There is a speed sensor to detect the drum speed and adjust it to the appropriate speed.

[0051] Pin 8 of the driver module TLP250 is connected to the +18V power supply, pin 5 is the ground, and pins 1 and 4 are left vacant. The function of the current limiting resistors R2 and R4 is to prevent the PWM signal from being deformed.

[0052] It can be understood that the above-mentioned technical features can be used in any combination without limitation.

[0053] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A protection circuit for an eddy current dynamometer, characterized in that: It includes a single chip computer main board, an eddy current machine protection board, an eddy current machine loading circuit, and a lifter solenoid valve; The single-chip computer mainboard includes a single-chip computer control system for receiving and processing a vehicle positioning signal, and a rising relay and a falling relay for outputting the vehicle positioning signal; The eddy current machine protection board comprises a first relay (Z1), a second relay (Z2), a normally closed switch (Z3) connected to the first relay (Z1), and a normally open switch (Z4) connected to the second relay (Z2); The first relay (Z1) and the second relay (Z2) are electrically connected to the lifter solenoid valve respectively to send signals to the lifter solenoid valve respectively; The eddy current machine loading circuit comprises an AC contactor (K) and an excitation coil (L) which are electrically connected, the AC contactor (K) comprises a contact coil (K1) and a contact switch (K2), the excitation coil (L) is installed on the stator of the eddy current machine and is in communication connection with the eddy current machine loading circuit; The normally closed switch (Z3), the normally open switch (Z4), and the contact coil (K1) are connected in sequence, and the normally open switch (Z4) and the contact switch (K2) are connected in parallel; The raising relay is connected to the first relay (Z1), the lowering relay is connected to the second relay (Z2), and the AC contactor (K) is energized or de-energized according to the on / off states of the raising relay and the lowering relay.

2. The protection circuit of the eddy current dynamometer according to claim 1, characterized in that: The eddy current machine protection plate is connected to an emergency switch (E) for controlling the AC contactor (K).

3. The protection circuit of the eddy current dynamometer according to claim 1, characterized in that: The eddy current machine loading circuit also includes a power semiconductor device IGBT connected to the excitation coil (L).

4. The protection circuit of the eddy current dynamometer according to claim 3, characterized in that: The protection circuit also includes an electrically connected fast-blow fuse (F) and a rectifier bridge (B). The current is converted into pulsating direct current by the rectifier bridge (B), and then inverted by the power semiconductor device IGBT to provide excitation current to the excitation coil (L). The fast-blow fuse (F) is configured with a rated current.

5. The protection circuit of the eddy current dynamometer according to claim 3, characterized in that: The protection circuit also includes an eddy current machine driving board connected between the single-chip computer mainboard and the eddy current machine loading circuit, so that the single-chip computer mainboard outputs a driving signal to the eddy current machine driving board; and controls the on and off of the eddy current machine loading circuit according to the driving signal received by the eddy current machine driving board.

6. The protection circuit of the eddy current dynamometer according to claim 5, characterized in that: The eddy current machine driving board includes electrically connected current limiting resistors R2, R4, a driving module TLP250, and a driving resistor R1. The current limiting resistors R2 and R4 are connected to the single chip mainboard, and the driving resistor R1 is connected to the power semiconductor device IGBT.

7. The protection circuit of the eddy current dynamometer according to claim 6, characterized in that: The PWM signal output by the single-chip computer mainboard is connected to the positive pin 2 and the negative pin 3 of the driving module TLP250 respectively through the current limiting resistor R2 and the current limiting resistor R4, and is output as a voltage signal from the pin 6 and the pin 7 of the driving module TLP250 after voltage and power amplification by the driving module TLP250, and is connected to the control electrode G of the power semiconductor device IGBT through the driving resistor R1, so that the conduction time of the power semiconductor device IGBT changes with the duty cycle of the PWM signal, and the current passing through the excitation coil (L) also changes, thereby changing the drum speed.

8. An eddy current dynamometer, characterized in that: A protection circuit for an eddy current dynamometer comprising any one of claims 1 to 7.

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