Home Forums General Discussion Technical Questions Delta Delta Start

I have a Westinghouse REL job that has the big generators with exciters, regulators. I've heard of this start circuit before (with the starting grid resistors on top of the controllers) where 5 picks and stays picked when 11A picks. I understand the resistors in the 5 side of the circuit limit the inrush and allow the armature to get up to speed and voltage output on the exciter to get up and then 11A picks and 5 stays up. I have no info on the AC windings and connections, the prints just show T1-2-3 going to the AC motor generator. L1, L2 and L3 connect to T1, T2 and T3 and go to the generator AC end and connect to "pairs" of wires which I assume are 1 & 12, 2 & 10 and 3 & 11. I'm used to 1,2,3 + 10,11,12 and tying 4 to 7, 5 to 8 and 6 to 9 when wiring one up for high voltage 480. Any insight on this start configuration would be most appreciated.

hey E-man, the setup you are inquiring about is a external wye connected motor, not a delta connected setup. It is basically a modified across the line starter with the modification being the insertion of the grid resistors to limit inrush current so that you could have a smaller kva rating of the incoming power, not to mention lower rated fuses and smaller gauge wiring. as far as the connections go, it depends on the Input voltage High, or Low. For High voltage, the connections are L1-t1, L2-t2, L3-t3, tie together 10-11-12, and 4-7, 5-8, 6-9. I had one of these grid resistors insulation go bad, and when the generator started, the grid resistor was shooting hot chunks of grid across the machine room, very scary. It cost to much to redo the grids, so we ended up putting in a Soft starter. I could not use any of the siemens products at the time, since this was a 75 horsepower across the line motor, we had to use one of the ABB PST series soft starters, It worked great. It really is intimidating when you start working on generators this big, it took me a little while to get it all working, as i was pretty nervous turning it on the first time.

Hey Scott, thanks for your reply. Here's what I had: L1,2,3 in the controller jumped to T1,2,3 in the controller. Then T1,2,3 went to the generator. The T1,2,3 wires going from the controller to the generator AC end were connected like this: T1 - hooked up to 2 wires, T2 - hooked up to 2 wires, T3 - hooked up to 2 wires. On one of the 2 wires were 10, 11, 12 labeled with wire markers. Then there were 3 other pairs tied together which I assume are 4-7, 5-8, 6-9. The only wires were marked were the 10, 11, 12 and I just rang out T1,2,3 from the controller to the generator. I understand your external wye connection but this motor didn't appear to be wired that way. It appeared to be the external Delta connection below. Here's external wye on a high voltage:

Voltage Conn. L1 L2 L3 Join
High WYE 1 2 3 4&7, 5&8, 6&9, 10&11&12

It appeared to be wired this way (which is described as external Delta):

Voltage Conn. L1 L2 L3 Join
High Delta 1,12 2,10 3,11 4&7, 5&8, 6&9

I may look at some other generators to see if they have markings on the T-leads. I got those from here:

Motor Connections Diagrams

cant understand why its labelled like this it just confused everything. i would say every genny in aus is star delta wired. a 3 phase motor has 6 wires from the windings. with external change over the wires just should be marked where they go from/to the controller. ie t1,t2,t3 and t4,t5,t6. on star start up you will have t4,t5,t6 shorted so the wires should be marked the same. also on delta t4 to t2,t5 to t3, and t6 to t1 should be shorted and again if the wires are marked the same it just takes out the comfusion as you dont have to work it out if you lose prints. i take it that the 7,8,9 and 10,11,12 are the wires that go to the controllers?

hey e-man, you are right, if it connected the way you say it is a Delta configuration, strange the one i had was a wye connected unit. Cant say that I have ever seen a motor connected just in the delta. Learn something new every day. Is the generator you have very big?

Scott, yes the generator is pretty big (long). It has an exciter, generator and a regulator on it. Not the biggest I've seen as it's about 14 stop, 350FPM geared Westinghouse REL.