Variable Frequency Drive

Sorry mate - can't make head nor tail of that.

Without knowing what type of electric motor is being used (3Φ induction, brushed synchronous, capacitor start, shaded pole, universal, stepping) I cannot say if a motor reversal cannot happen but it is a remote possibility. Certainly a stopped flywheel with sufficiently tight belts could stall this motor. Hopefully circuit protection devices will trip and prevent a fire from happening if the motor stalls.

This is going to depend on the size and weight of the flywheel plus its rotational speed at the time the stop command is given.

If the flywheel is not too large or travelling very fast, and the motor has some form of braking (disc or DC etc.) then you may be able to bring it to a complete stop on command. Too much inertia and you will do damage.

Winding the VFD down will impart a certain degree of regenerative braking to the motor when it is below synchronous speed, but this may not be sufficient for your needs

For starting, the inertia of the flywheel must be overcome, so again depending on size etc. as above, there may be an unacceptable time lapse before getting to required speed.

If you attempt to reverse the motor (depending on motor size also, as momentary reversal "plugging braking" can be used as a form of soft brake, and may suit your requirements) while the wheel is going in the opposite direction at a fair rate of knots you may break a belt, do some mounting damage or even damage the VFD.

A brake on the flywheel itself may be an option for more accurate control.

i appreciate to all reply , weight of wheel is 60 kg , r p m of wheel is 60 rounds per minute , see video link to understand my concept https://www.youtube.com/watch?v=55evPP8fPOU

I wouldn't stop it with a command. I'd stop it with a brake.

In an emergency, pressing the emergency stop button should stop every moving part.

However this would not be good for the lifespan of the mechanical components, due to the stresses.

This however is not only due to the flywheel, instead every moving thing tends to stay in motion, therefore wanting to stop it will have to be done by applying a force.

Instead for stopping the motor, if at all necessary, should be done by decreasing the frequency and letting it stop in a controlled and (relatively) stress free way.

Inertia, inertia, inertia. Oh yeah and inertia.

Why are you trying to stop the motor

- emergency break ?

- just a normal switch on-off after the work is done ?

An emergency break is probably practically not possible with a frequency drive. You need a frequency drive with a breaking resistor, a motor that is powerfull enough to decelerate the inertia in a very short timespan, belts and pulley arrangements that are strong enough to survive the breaking forces. In some cases you may need to inject DC current in the motor to break it faster.

According my opinion, a clutch between flywheel and application together with a mechanical brake on the application would be a better solution. Perhaps a safety fence in front of the machine?

A normal switch on - off with a frequency drive is possible, if the deceleration time is chosen long enough.

I agree. A clutch between the flywheel and a brake after the clutch is probably your best bet. The fly wheel stores mechanical energy that came from the electric motor. If the motor was capable (strong enough) to quickly remove all of the energy from the spinning flywheel then there would be no need for a flywheel at all.

I applaud the OP effort for adding some safety systems to this bracket making machine. If the OP has a concern for the safety around the still spinning flywheel then a simple custom exclusion zone cage around the flywheel and clutch will answer that.

Typically the sort of machine you illustrated in your subsequent post should a safety interlock that decouples the flywheel from the machine (load) during safe (operator hands within active zone of machine) non-motion required time. This is not the same as a safety situation where lockout and tagout requires that all forms of energy to the machine be discharged and locked (thus no spinning flywheel). The flywheel is there to store up energy from the drive motor, and the VFD serves the purpose (on a 3 Ph induction motor) of smooth motor (and flywheel) acceleration without excessive torque loads. Sudden emergency stop should not be electric control through the VFD, but should include a physical braking system, in which case this can be electronically linked to output power from the VFD such that if the mechanical brake is engaged, the VFD is shut down, tripped, etc. The mechanical brake design should be sufficiently robust to stop the flywheel within one turn.

There should be a completely separate action to engage machine motion on the output shaft of the flywheel.

Dear Mr. metal master engg:

The dynamic Inertia of the fly wheel will keep the system to rotate in the same direction. If you want a momentory stop, you should have a brake with sufficient torque.

While starting, it needs time to build up speed since inertia will decide the rate of increase of speed.

DHAYANANDHAN.S

The machine is inherently dangerous, no guarding, manual feed, etc, etc, do you intend to do anything about this?

Personally I'd consign the machine to the scrap heap.

A magnetic hold off brake on the flywheel along with a magnetic clutch would help. Pressing an e-stop would cut the power to both the brake and clutch.

I agree with many comments:

1. Put guards around any components that cannot be stopped quickly.
2. Insert a clutch/brake assembly between the flywheel and the driven load. This should be activated by the emergency stop circuit, and should be sized to absorb the total inertia of the driven load within the time limit set by your local safety rules.
3. VFD's generally have two stopping modes--ramp stop and coast stop. In a ramp stop, the VFD is pulling energy from the motor and putting it into its DC bus by increasing the bus voltage. If this voltage exceeds the VFD's safety limits, the VFD will automatically switch to a coast stop--so the stop can then take minutes.
4. If you have a DC braking resistor attached to the bus via a contactor, as documented in the VFD's instructions, you can set it to activate and shunt the excess energy from the DC bus before the DC bus voltage exceeds its safety limit, so the switch to a coasting stop would not be likely.
5. If the VFD is a line regenerative drive, then the excess energy of the motor being ramp stopped will be injected back onto the incoming mains. Components for this need to be carefully designed/selected.
6. Program the VFD to start into a rotating load, instead of a stopped load. This will be one of the many parameters available to you, and will allow the VFD to re-start even if the flywheel and motor are not stopped, without sudden mechanical and electrical damage to the equipment (including the VFD). When programmed to start into a rotating load, the VFD will be monitoring the voltage and frequency being generated by the motor (it is acting like a generator when it is still turning but not being powered), so the VFD's output can match the frequency being output by the motor when the VFD "turns on".
7. If you are unsure about any of these things, GET HELP. However, don't be afraid to ask questions--just make them intelligent ones by reading and studying as much as you can first.
8. Rotation anti-clockwise (counter-clockwise for some) is only allowed if the VFD is programmed for that direction of rotation (assuming the motor is 3ø).

--JMM