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- Jun 12, 2014
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It depends on the type of motor, a TENV and TEBC are rated down to 0 speed, a TEFC which is the usual style of mill motor, around 15 Hz for any length of time. Below that point there is a higher chance of insufficient cooling. Depends a lot on the motor design, mass, type of load, duration, ambient temperature, etc. Since you loose Hp in a linear fashion below your base speed and you loose the mechanical advantage, turning down the VFD below 20 Hz you are operating with a significant reduction in power. So OK for light tapping/drilling, but less ideal if you are hogging out a lot pf metal.
Inverter/vector TENV motors and some TEFC motors often have temperature sensors in the motor that can be wired into the VFD to shut down if the motor overheats. A TENV typically barely gets warm at any speed, installed in manual mills and lathes.
Inverter/vector TENV motors and some TEFC motors often have temperature sensors in the motor that can be wired into the VFD to shut down if the motor overheats. A TENV typically barely gets warm at any speed, installed in manual mills and lathes.