Static phase conv. or motor problem

Am running a 7.5 HP, 3ph. motor with 8hp static converter and blew my 30 amp fuse(motor safety fuse)for the 2nd time. this was after motor was running, both times. now after 2nd time i cant get motor to start now.it rattles & keeps blowing fuses. This motor powers a Hyd piston pump running at only 500 to 1000psi, so there is no heavy load on motor. I also hooked motor up direct to 3 phase & it run fine but I was bypassing fuses. My Question is if the static conv is the problem starting,what made fuses blow after it was running when conv is no longer doing anything? Motor amps is 21 & I have 30 amp fuses. Any help would be appreciated.

Incidently I was formerly GregM in this Forum.My 25 year marraige went caput 3 months ago & moved so I just got back on internet! I wouldnt wish a Divorce on my worst enemys.

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I got divorced, seperated in 97, got kids, took 2 1/2 yrs to sort out deal etc. It has been a long 7 years , the kids get the worst of it. I am now remarried to a wonderfully supportive woman, so life gets better.

Greg,

In general, powering any type of compressor is difficult even for a well-built RPC. All the time when this is done, I fit the idler with a heavy multigrooved sheave on its shaft to act as a flywheel.

The problem with running a compressor, or a hydraulic piston pump, is starting. Even though you say 500 - 1000 psi is low pressure, the motor driving that pump doesn't agree with you when it's at a standstill. This is true even with an unloader.

I would not even dream of attempting to run any kind of compressor via a static converter, unless that static converter were of the autotransformer (i.e., Ronk Add-A-Phase) type.

I think your problem is the static converter. I had a customer who bought a 10hp alligator shear that had a static converter. When he would "load" the shear, the motor would slow down, and the static converter would reenergize. He burned up two statics before he called me. I built him a 20hp RPC and all is well. Keep in mind that a 3ph motor running on single phase (such as provided by a static converter) only developes about 60% of its rated horsepower. You need a rotary phase converter.

I think you can probably buy a new rotary converter at www.deselectric.com cheaper then you can buy the parts and motor to build one. Hope that helps you out. They gave me a great deal.

Dear All,

I have recently purchased an elderly but well kept Smart and Brown Model 1024ss/cc lathe. This lathe is now in my small workshop awaiting connecting to some power. I have a Transwave static converter with a max motor loading of 4.0KW and have tried connecting this to the lathe (T1, T2, T3 neutral and of course earth). I can hear the coolant motor buzz when its turned on but do not have any response from the main motor apart from a deep buzzing.

The lathe motor is 3 speed, 2.5hp, 2hp and 1.5hp. I am not sure how the speed is achieved weather it be gears or coils? It is however the original motor.

Any advise here would be much appreciated. Am I connecting the Transwave converter incorrectly or is the converter of too small a power? Should it be a rotary and not a static.

My limited electrical knowledge is my downfall here but perhaps one of you more experienced engineers can advise on this?

Thankyou!