Just need some advice for calculating the size of supply for a 3 phase dust extraction unit. In the past i've worked with 3 phase so understand how to do it but this has always been whilst working for other firms who give you the materials and tell you to get on with it. Now that i'm self employed the buck stops with me so i just want to check that i'm correct with my calculations/assumptions.
The motor in question has this rating plate on it:
Based on this i understand it's a 7.5kW motor with a power factor of 0.88. So i would you calculate the load per phase as being the following:
7500/(400V*root 3*0.88)=12.3A per phase.
I would then assume that a 16A supply on a C type breaker is necessary and based on a run of no more then 20m to the motor a 4mm SWA would be more then adequate (could get away with 2.5 but the workshop is a bloody long way from the incoming supply so limiting the volt drop as much as possible seems sensible).
Does all of the above add up?
Finally, the extractor unit is outside the workshop with the controller inside, my intention is to fit a lockable rotary isolator beside the controller to allow for safe isolation for mechanical maintenance. Is this the best option or would you consider putting 2 further isolators nearer to the extractor unit (it has 2 motors, the main one for the fan and a smaller one for a filter shaker). My only issue with putting additional isolation outside is that it gives people the scope to mess about with the isolation switches as the unit is in an unsecured area on a farm that is easily accessible.
Any feedback would be gratefully received.
The motor in question has this rating plate on it:
Based on this i understand it's a 7.5kW motor with a power factor of 0.88. So i would you calculate the load per phase as being the following:
7500/(400V*root 3*0.88)=12.3A per phase.
I would then assume that a 16A supply on a C type breaker is necessary and based on a run of no more then 20m to the motor a 4mm SWA would be more then adequate (could get away with 2.5 but the workshop is a bloody long way from the incoming supply so limiting the volt drop as much as possible seems sensible).
Does all of the above add up?
Finally, the extractor unit is outside the workshop with the controller inside, my intention is to fit a lockable rotary isolator beside the controller to allow for safe isolation for mechanical maintenance. Is this the best option or would you consider putting 2 further isolators nearer to the extractor unit (it has 2 motors, the main one for the fan and a smaller one for a filter shaker). My only issue with putting additional isolation outside is that it gives people the scope to mess about with the isolation switches as the unit is in an unsecured area on a farm that is easily accessible.
Any feedback would be gratefully received.
I'm finding my new iPhone is surprisingly handy for various bits on site, there's even an app that turns it in to a torch for those moments when a quick inspection in a dark area is required!
