Transistor H-bridge system for a conveyor motor with speed control property's

[Didawdidaw]

Hey, I've been asked a question 'what are operational systems on Transistor H-bridge system for a conveyor motor with speed control property's'. I know that system I've put below would work for a lower voltage application, I just cant seem to find any information on high voltage applications. I know how the H-bridge system works but I just don't know what would be used for the speed control. I'm assuming a 555 chip wouldn't be powerful enough to operate a conveyor system? I'm just wondering what another option would be for this application if a 555 chip wouldn't cut it?

I'm also basing this on it being a 1-phase system. I'm hoping that I can get away with a 1 phase system because I don't know how I would draw a 3-phase H-bridge system. Could this application get away with being 1-phase or would i need to look in to 3- phase.

So far this is my answer:
On a 12 volt system when the voltage is supplied to T3 and T2’s side this will open T2. This is because the voltage on T2 between the gate and source will be 11.45 volts, where as the voltage to between the gate and source on T3 will be -0.55v closing the gate. Whilst this is happening on T3 and T2 side the opposite will be happening on T1 and T4’s side, T1 will have -12 volts opening the transistor; letting the power travel from T3 to T4. When power to T1 and T4’s side is present this will do the same in reverse opening T1 and T2. Having T1 and T2 open will make the motor spin one way and when T3 and T4 are open this will spin the motor the other way. The Voltage for a conveyor system will be a lot higher, therefore the components used will have a higher voltage but the same principle will apply

Any help would be much appreciated, as the questions I get are based around things that I haven't been taught about in the slightest.

 

[SparkyChick]

So the 555 isn't doing any switching, it's providing the pulse train to do pulse width modulation for the speed control. For a high voltage version, it would be a case of changing the drive transistors and associated components.

For reference, for a 3ph AC application, you'd probably just use a variable frequency drive with reversing capabilities.

 

[Didawdidaw]

So the 555 isn't doing any switching, it's providing the pulse train to do pulse width modulation for the speed control. For a high voltage version, it would be a case of changing the drive transistors and associated components.

For reference, for a 3ph AC application, you'd probably just use a variable frequency drive with reversing capabilities.

Ah okay, so if I changed all of the components on the lower part of the circuit to accommodate a higher powered motor and stuck with 1 phase mains power on it this circuit could theoretically run a conveyor system? It doesn't realy matter about how effective it would be as long as it would work.

Thanks

 

[Simon47]

Basically yes - rate the components appropriately and it'll run any size system. But of course, the more powerful the system, the harder it is to design a system that's both safe and efficient. One critical fault mode in H bridges is to allow both transistors in a pair to conduct at once - that shorts out the supply and lets the magic smoke out.
Also, in practice, when you reduce the speed, you also need to reduce the voltage or the motor windings get a bit hot.
So commercial drives tend to use high frequency chopping to synthesise a sine wave of variable frequency and voltage.
Instead of the simple control curcuit you have - I think every drive these days will by computer controlled with each transistor independently controlled.

Finally, for 3 phase you add one more pair of transistors for a total of 3 pairs - each pair connected to each phase.

 

[marconi]

Probably just me but I am not clear on what you are asking. I 'think' you are asking what type of controller is required to drive an H bridge controlled motor powering a conveyor belt.

I have never worked on a conveyor belt but the nature of it suggests to me that the controller must have the following 'operational capabilities':

(not exhaustive)

1. closed loop speed control with a speed setting capability;
2. 'Soft start/stop' or ramp up in speed from stationary and ramp down to stop to avoid damaging the belt by stretching it;
3. Emergency stop - a fast version of (2) above;
4. Overspeed detection if the belt breaks to cut off power to the motor;
5. Overload detection to stop the conveyor if thee is too much on it or too high a tension in the belt;
6. An inch along capability (to check the belt as it runs before one's eyes) and to allow time for items to be put on or taken off perhaps;
7. A slow reverse direction mode (through a controlled stop if already going forwards).
8. True belt position tracking and then (9);
9. A 'go to' belt section capability for specific examination of a belt section and to move an item on the belt to a desired position further down the line;
10. MAximum allowed error(speed and position) detection to shut down belt.

 

[marconi]

Didawdidaw: You also ought to ponder and study the requirement for the controller to minimise and dampen down the tendencies of the complete electro-mechanical system to oscillate and hunt - since a conveyor belt system is a glorified distributed mass - elasticity system.

 

[Simon47]

... the nature of it suggests to me that the controller must have the following 'operational capabilities':

That really depends on it's function.
For many, it's simply to move "stuff" from A to B at an approximately controlled speed. An inverter drive with induction motor is going to give you that - the motor will never over-speed faster than it's supply frequency, so the difference between no load (snapped belt or whatever) and full load is never going to be more than the slip frequency in the motor under full load. A simple inverter drive will give you overload and ramp up/ramp down/reverse as base functions.
Now, if you are talking about precision positioning, e.g. delivering parts to machining cells along a line, then that's a whole new can of worms - but I suspect most of those are designed on the basis of detecting the precise position of the item rather than precise movement of the belt.

 

[Shoei]

Hey, I've been asked a question 'what are operational systems on Transistor H-bridge system for a conveyor motor with speed control property's'. I know that system I've put below would work for a lower voltage application, I just cant seem to find any information on high voltage applications. I know how the H-bridge system works but I just don't know what would be used for the speed control. I'm assuming a 555 chip wouldn't be powerful enough to operate a conveyor system? I'm just wondering what another option would be for this application if a 555 chip wouldn't cut it?

I'm also basing this on it being a 1-phase system. I'm hoping that I can get away with a 1 phase system because I don't know how I would draw a 3-phase H-bridge system. Could this application get away with being 1-phase or would i need to look in to 3- phase.

So far this is my answer:
On a 12 volt system when the voltage is supplied to T3 and T2’s side this will open T2. This is because the voltage on T2 between the gate and source will be 11.45 volts, where as the voltage to between the gate and source on T3 will be -0.55v closing the gate. Whilst this is happening on T3 and T2 side the opposite will be happening on T1 and T4’s side, T1 will have -12 volts opening the transistor; letting the power travel from T3 to T4. When power to T1 and T4’s side is present this will do the same in reverse opening T1 and T2. Having T1 and T2 open will make the motor spin one way and when T3 and T4 are open this will spin the motor the other way. The Voltage for a conveyor system will be a lot higher, therefore the components used will have a higher voltage but the same principle will apply

Any help would be much appreciated, as the questions I get are based around things that I haven't been taught about in the slightest.

Is that the full question? If so it doesn't say anything about high voltages, conveyors aren't always high-voltage/power, think of the conveyor on a supermarket checkout for example. Part of your answer could be that the properties of an H bridge drive are limited to low-voltage applications.

Your circuit would sort-of work with a DC supply up to about 18V, the maximum for a 555, there will be a large range of gate voltage swing with both transistors turned on, which would be interesting, think about circuitry to add a bit of off time during the transition and/or add resistors in the drains to limit current.

For higher voltages it would get a bit more complex. If there's more to the question post it here and maybe someone can help.

 

[Didawdidaw]

Thanks for all of the replies, I really appreciate all of the comments. For the task that I've been given I think that the system that I've supplied would be sufficient as it doesn't specify what the conveyor has to run. I think that I've answered the question correctly as it doesn't need to be a super technical answer for this question. For those curious the question was :

'As an alternative to the AC system in task 5, you have also been asked to produce a circuit design that can control the speed and direction of the conveyor such as an AC to DC motor thyristor and transistor H-bridge drive system. With reference to appropriate diagrams, an example and research evidence discuss

1.the operational features (how it works with speed and direction circuit diagrams)

2.how it can be applied a conveyor (with a schematic diagram of the controller connected to a conveyor)

Guidance: Requires schematic/circuit diagrams. Select electronic drive/controls rather than mechanical relays and resistors (400 words)'

The answer that I've supplied is:

'Transistor H-bridge system

On a 12 volt system when the voltage is supplied to T3 and T2’s side this will open T2. This is because the voltage on T2 between the gate and source will be 11.45 volts, where as the voltage to between the gate and source on T3 will be -0.55v closing the gate. Whilst this is happening on T3 and T2 side the opposite will be happening on T1 and T4’s side, T1 will have -12 volts opening the transistor; letting the power travel from T3 to T4. When power to T1 and T4’s side is present this will do the same in reverse opening T1 and T2. Having T1 and T2 open will make the motor spin one way and when T3 and T4 are open this will spin the motor the other way.

The speed control system will use pulse with modulation (PWM) which is the system at the top of the circuit diagram. This system will use frequency to control the speed of the motor by changing the pulse width. This changes the speed of the motor by changing the overall voltage going to the motor.

The diagram above would work on a low voltage conveyor system, though some of the components may need to be changes so that a higher voltage could be used (the drive transistors and the associated components). This system would look like the picture on the left when it’s installed. The power supply would be connected to the control circuit and the control circuit would house all of the components of the circuit apart from the motor which will be place as shown. This would be so that start, stop and speed control can be operated with ease.'