1. Well, there's no real argument here, as we're just discussing semantics. I learned something, and I agree with him, too. The wye-delta starter has no means of reducing the voltage at the motor terminals. However, the effect on the motor is the same as reduced voltage because in wye, the motor only sees 58% of the line voltage through each winding.

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When the windings of a 3-phase motor are connected in WYE:

The voltage applied to each winding is reduced to only (1 /.'/'3) [1 divided by root three] of the voltage applied to the winding when it is connected directly across two incoming power service line phases in DELTA.

The current per winding is reduced to only (1 /.'/'3) [1 divided by root three] of the normal running current taken when it is connected in DELTA.

So, because of the Power Law V [in volts] x I [in amps] = P [in watts],
the total output power when the motor is connected in WYE is:

PS = [VL x (1/.'/'3)] x [ID x (1/.'/'3 )] = PD x (1/3) [one third of the power in DELTA]

Where:
VL is the line-to-line voltage of the incoming 3-phase power service
ID is the line current drawn in DELTA
PS is the total power the motor can produce when running in WYE
PD is the total power it can produce when running in DELTA.

A further disadvantage when the motor is connected in WYE is that the total output torque is only 1/3 of the total torque it can produce when running in DELTA.

Attached is a good presentation of how a Trane closed transition wye delta starter works.

3. a wye delta motor is NOT a reduced voltage motor. it recieves the full voltage (that the building can provide) at all times (except in Open Transition starters).

Most (but not all) VF drives are reduced voltage starters.
Depending on how you look at it, a Solid State Starter is reduced voltage starter (but not really).
Primary Resistor is reduced voltage starter.
MultiPoint Reduced Voltage is a reduced voltage starter.
Auto Transformer is a reduced voltage starter.

a wye-delta starter is not a reduced voltage starter. changing the order of the windings does not change the incoming voltage. it does change the resistance and reactance of the motor...but the motor/starter is still full voltage.

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y/delta starter

WE cut the suction and liquid lines to the chiller barrel yesterday to pressure test it to see if it is leaking. I suppose if it is we will probably scrap it all. we have drained about 1 1/2 gal. of oil and the compressor is still at the top of the sight glass.WE could not get the service valves to seal even after opening and closing them several times. Thanks to whomever replied with that suggestion any way , even if it didn't work.

This method is actually reduced voltage but is accomplished by changing the motor phase connections such that a winding that is designed to run with phase voltage equal to line voltage on delta connection is wye connected for starting to put less than line voltage on each phase. Effectively, the voltage is reduced by 1.732 factor. The impedance seen by the power system is 3 times the impedance of the delta run connection.

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To all but mostly to Tech Rob,

wEare pressurizing mostly to see if there are any leaks. I ahve never had much succes with sniffers. I have had about 5 and we have a dtek but we alqays go back to dy e or an ultrasonic. Is there another way other than orssure testing to prove if asystem is leaking or not ? This thing has 100 ft line set of 1 3/8 liquid and 2 1/8" discharge to the air cooled condenser. Any ideas on how much a new evaporator or reciver would cost ? What would I do ; just get anew one from Carrier or similar ?

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Gee, I should proofread my text and improve my typing skills !

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Originally Posted by jayguy
a wye delta motor is NOT a reduced voltage motor. it recieves the full voltage (that the building can provide) at all times (except in Open Transition starters).

Most (but not all) VF drives are reduced voltage starters.
Depending on how you look at it, a Solid State Starter is reduced voltage starter (but not really).
Primary Resistor is reduced voltage starter.
MultiPoint Reduced Voltage is a reduced voltage starter.
Auto Transformer is a reduced voltage starter.

a wye-delta starter is not a reduced voltage starter. changing the order of the windings does not change the incoming voltage. it does change the resistance and reactance of the motor...but the motor/starter is still full voltage.
Yes, the motor TERMINALS receive full voltage no matter how it is configured so I guess in that aspect, it's a full voltage starter. But the INDIVIDUAL MOTOR WINDINGS receive reduced voltage when in wye configuration so in that aspect, it's a reduced voltage starter.

If you google 'reduced voltage starter' in almost all hits, wye delta is listed.

Who knows, maybe I'm wrong, but this is an interesting discussion.

8. Rob sorry i read the way i wrote that it was kinda argumentative, i guess its a glass half full/half empty situation all depends on how you view it, either way if you know how it works who cares what you call it

9. I got out some of my motor/starter books and it does say in both of them that it is similar to a reduced voltage starter but does not classify it as a reduced voltage starter, so my apologies.

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I've been researching this and it appears to be a matter of semantics as some starter books list it as reduced voltage starters and some don't.

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7 viewing ?

I see that there are seven viewing right now, I need to get my posts up so I want to give a short dissertation on electrical grounding. Where do I go to do that , sorry I know it is not here but since I started this thread I guess I could get by with asking another question here. Can I post my email address here in a thread ?

12. R123, the truth of the matter is that we're both right! lol

Thanks for helping me to look at that thing from a different perspective.

13. Originally Posted by johnnyb
To all but mostly to Tech Rob,

wEare pressurizing mostly to see if there are any leaks. I ahve never had much succes with sniffers. I have had about 5 and we have a dtek but we alqays go back to dy e or an ultrasonic. Is there another way other than orssure testing to prove if asystem is leaking or not ? This thing has 100 ft line set of 1 3/8 liquid and 2 1/8" discharge to the air cooled condenser. Any ideas on how much a new evaporator or reciver would cost ? What would I do ; just get anew one from Carrier or similar ?
Get yourself an H-10 sniffer. An H-10, some R-22, and some Nitrogen... You will find the leak. No need to get crazy with the pressure.

I can't speak to the cost of a new evaporator or receiver, or even where you could find a suitable non-OEM replacement.

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