Wound rotor motor 3

[NEWFIEBOY]

Hi Guys
I have a 1960s 15 hp 230 volt 3 ph wound rotor motor. It is presently connected to a motor starter and resistor bank. The motor is reversable and can be operated at either of three speeds selected by remote control switches. This motor is the power unit which operates a capstan on the deck of a tug boat. The problem is that the motor starter is original, it is not reliable, parts to keep repairing it are hard to find and expensive. I would like to replace the motor starter with a new AC drive. My question is has anybody had any experiences with using an AC drive along with an older wound rotor motor? Is it feasible to short circuit the rotor windings to make this motor resemble a squirl cage motor? I would appreciate any advice.

 

[ozmosis]

NEWFIEBOY
VFD's do create an increase of leakage currents due to the fact that capacitors are used internally, the VFD generally incorporates high switching frequencies and the recommended practice (in certain quarters) of shielded motor cable all come together to create higher leakage currents than you would generally want, especially on an installation that requires the hull to be the ground. It is only a problem if you do not take it into consideration prior to purchase/installation. There are many thousands of VFD/VSD's installed onto ships so it is not a problem as long as your supplier knows. We had a problem on a ship in the Med where somebody replaced an old damaged drive with a new one but installed it with a standard RFI filter. This filter has high leakage currents through the Y connection internally and kept tripping the GFD breaker. The leakage was in the 100's of mA so had the breaker not tripped then I imagine the sacrificial anode (correction on my earlier 'cathode') would erode quicker, although this is not my expertise I'm afraid.
So, don't worry about it, just make sure you talk to a reputable supplier who knows your VFD is going on a boat/ship/vessel (I was got my knuckles wrapped by calling a boat a ship or a ship a boat so now I call them everything, just to keep the peace...)