megloff11x
Senior Member
I propose that Article 430 add a new sub-section to cover servo motor and stepper motor systems separately from other motor types. Further, the requirements for these new servo motor and stepper motor sections should be determined by new testing.
In particular, I think that they should have different fuse/circuit breaker and wire size requirements than other motor systems.
Aside from inrush to the amplifier, which can be nipped by using a NTC inrush suppressor and a D-curve breaker, these systems just don't draw as much current as other motors.
If the controller amplifier prevents a locked rotor condition, you shouldn't need to make the motor wire big enough to withstand what it will never experience. Most of these controllers do prevent this from happening.
Many small servo and stepper motors are used in robotic or moving and positioning systems. The wire is flexed and twisted. Fatter wire breaks sooner, no matter how well the manufacturer's high continuous flex & torsion guidelines are followed. And this too should be in the code.
If the motor is drawing less than an amp, why do I need to use 14AWG or even 18AWG wire? Why not 22AWG or 24AWG? Is it safer to have a cable of 14AWG wires that kneads itself into a break or short in a few months, than a 22AWG that lasts for years and never gets warm?
The hazardous location issue also needs to be addressed. Most "suitable" conduit doesn't last long when continuously flexed and twisted. Article 500 and subsequent articles allow for shielded flexible cable to be used without conduit in certain cases. The code should make moving motor connections a part of this.
Basically we have motor systems that are different enough to merit their own rules. Their rules should take into account system needs of smaller wire and moving parts.
In particular, I think that they should have different fuse/circuit breaker and wire size requirements than other motor systems.
Aside from inrush to the amplifier, which can be nipped by using a NTC inrush suppressor and a D-curve breaker, these systems just don't draw as much current as other motors.
If the controller amplifier prevents a locked rotor condition, you shouldn't need to make the motor wire big enough to withstand what it will never experience. Most of these controllers do prevent this from happening.
Many small servo and stepper motors are used in robotic or moving and positioning systems. The wire is flexed and twisted. Fatter wire breaks sooner, no matter how well the manufacturer's high continuous flex & torsion guidelines are followed. And this too should be in the code.
If the motor is drawing less than an amp, why do I need to use 14AWG or even 18AWG wire? Why not 22AWG or 24AWG? Is it safer to have a cable of 14AWG wires that kneads itself into a break or short in a few months, than a 22AWG that lasts for years and never gets warm?
The hazardous location issue also needs to be addressed. Most "suitable" conduit doesn't last long when continuously flexed and twisted. Article 500 and subsequent articles allow for shielded flexible cable to be used without conduit in certain cases. The code should make moving motor connections a part of this.
Basically we have motor systems that are different enough to merit their own rules. Their rules should take into account system needs of smaller wire and moving parts.
