I am a small electrcial contractor who works on some 3 phase items here and there, I feel confident in what I know about it, so here is my problem... We are hooking up a resturant exhaust fan , this is a 3 ph 120/208 2 speed unit. It has 6 wires on the motor listed T1-T6 . It came with a small junky little speed control switch that has the options of ( low off high ). we ran all our wires to it and checked rotary field with our tester before any power went to motor. it works fine on low speed but when we switch it to high it will run about 1 minute and blow the fuse protecting L3 line. we have used time delay and instant fuses all at 20 amps. the motor gets real hot and when you turn it off you can smell it cooking. We have used a continuy meter all of our wire's to make sure nothing is crossed, it isnt. so out of desperation we bypassed the speed control and hooked up direct and ran the motor at low speed and it works perfect, switched around the power leads and motor taps to make it run at high speed , same thing, gets hot and smokes. this is a BRAND NEW unit, can motor be bad like this from the factory? I have never ran across this before ever , and I have checked out my wiring 2 times , and always used a rotation meter before shooting power to the motor. I am lost , any help pleaseeeeeee???
