'Soft-Stop' Mechanical Brake for Induction Motor???
'Soft-Stop' Mechanical Brake for Induction Motor???
(OP)
Known:
Class 1, Division 1, Group C & D environment
5 HP Induction Motor with a impeller type blade attached.
Local (at motor)Disconnect.
Blade can be accessed before motor comes to a stop.
In a non-hazardous environment we typically supply a solenoid to latch the access till motor spins down. Haven't had any luck finding a commercially available solenoid that has certs to operate in hazardous environment.
Question, is there a way to mechanically 'soft-stop' the motor/blade when power is cut via the disconnect?
Any comments, ideas or discussion welcome.
Thanks in advance.
Class 1, Division 1, Group C & D environment
5 HP Induction Motor with a impeller type blade attached.
Local (at motor)Disconnect.
Blade can be accessed before motor comes to a stop.
In a non-hazardous environment we typically supply a solenoid to latch the access till motor spins down. Haven't had any luck finding a commercially available solenoid that has certs to operate in hazardous environment.
Question, is there a way to mechanically 'soft-stop' the motor/blade when power is cut via the disconnect?
Any comments, ideas or discussion welcome.
Thanks in advance.
"To be or not to be, that is the question" - William Shakespeare via Hamlet





RE: 'Soft-Stop' Mechanical Brake for Induction Motor???
"You measure the size of the accomplishment by the obstacles you had to overcome to reach your goals" -- Booker T. Washington
RE: 'Soft-Stop' Mechanical Brake for Induction Motor???
RE: 'Soft-Stop' Mechanical Brake for Induction Motor???
ice
Harmless flakes working together can unleash an avalanche of destruction
RE: 'Soft-Stop' Mechanical Brake for Induction Motor???
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: 'Soft-Stop' Mechanical Brake for Induction Motor???
I also like the idea of using a VFD, BUT, with the disconnect at the motor, it would be possible for the motor to be running at full speed and the operator could kill it with the disconnect, if that is done, then the VFD braking is null-and-void. So, what I am trying to achieve with the mechanical solution would have to stop the motor, only in the advent of the disconnect being used. Otherwise, I can just use a VFD. Comments, roasts, ideas, questions?
"To be or not to be, that is the question" - William Shakespeare via Hamlet
RE: 'Soft-Stop' Mechanical Brake for Induction Motor???
In your case you can't verify the crew waited for the motor to stop after opening the disconnect, before they opened the cover. Even with a good, consciencious crew, you want to verify.
Following that, how would you verify the crew hit the stop button before opening the disconnect and then immediately opened the cover? I agree, a VFD driven stop is likley not a solution for this.
ice
Harmless flakes working together can unleash an avalanche of destruction
RE: 'Soft-Stop' Mechanical Brake for Induction Motor???
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: 'Soft-Stop' Mechanical Brake for Induction Motor???
ice
Harmless flakes working together can unleash an avalanche of destruction
RE: 'Soft-Stop' Mechanical Brake for Induction Motor???
If the VFD must be in the same classified atmosphere, the cost to enclose / purge and cool the VFD and braking resistors may prove to be prohibitive, depending on what size you are talking about (you never said). It might be less expensive to just create an overly complex mechanical interlock system that takes longer to implement than it takes for the blade to coast to a stop. For example place the key trap behind another trapped key system separated by a distance. I had to do that once on a production bread slicer which, for various reasons, could not be braked to a stop, so workers were opening the access hatch when the blades were still moving and basically invisible. We made them go through 4 steps to get access to the hatch, which we timed out to be 3x the spin down time of the blades.
"You measure the size of the accomplishment by the obstacles you had to overcome to reach your goals" -- Booker T. Washington
RE: 'Soft-Stop' Mechanical Brake for Induction Motor???
then your disconnet opens the power leads and shorts them together; bingo, stop. Add resistor(s) for complete 'soft stop' decel rate....
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