Wye Delta Breaker Tripping Problem
Wye Delta Breaker Tripping Problem
(OP)
Scenario is as follows:
I have a 460VAC, 60Hz,3 phase, 1750RPM, 500Amp induction motor designed to
operate on a 480VAC Wye start/ Delta run starter system.
When a different motor was tested on this machine, it starts properly and
there is little load on the dual output shafts(About 25% of the full load
amps).
Each shaft has a hydraulic pump attached that spins easily.
The Main breaker trips off when the problematic motor transfers from Start
to Run.
Why?
The motor has 12 leads.
They are numbered as follows: 1,1 2,2 3,3 4,4 5,5 and 6,6.
The motor leads continuity test as follows:
1,1 to 4,4.
2,2 to 5,5.
3,3 to 6,6.
The motor is connected to the starters as follows:
L1 to 1,1 L2 to 2,2 L3 to 3,3 on the Main breaker (no Main contactor)
L1 to 6,6 L2 to 4,4 L3 to 5,5 on the Delta run contactor
6,6 4,4 5,5 on the Wye start contactor also.
The phasing from the Main breaker to the motor leads connections has been
verified as correct for the Wye/Delta configuration.
The Main breaker is a 700Amp shunt trip breaker. It can be shunt tripped from the Overload relay or motor thermal sensors, as well as tripping from overcurrent. The adjustable trips are set at Maximum.
The starting sequence is:
The Wye start contactor is closed first.
The motor ramps up to speed in the correct rotation.
After 5 seconds the Wye start contactor opens and the Delta run contactor
immediately closes.
Wham! The breaker trips.
Why?
I have a 460VAC, 60Hz,3 phase, 1750RPM, 500Amp induction motor designed to
operate on a 480VAC Wye start/ Delta run starter system.
When a different motor was tested on this machine, it starts properly and
there is little load on the dual output shafts(About 25% of the full load
amps).
Each shaft has a hydraulic pump attached that spins easily.
The Main breaker trips off when the problematic motor transfers from Start
to Run.
Why?
The motor has 12 leads.
They are numbered as follows: 1,1 2,2 3,3 4,4 5,5 and 6,6.
The motor leads continuity test as follows:
1,1 to 4,4.
2,2 to 5,5.
3,3 to 6,6.
The motor is connected to the starters as follows:
L1 to 1,1 L2 to 2,2 L3 to 3,3 on the Main breaker (no Main contactor)
L1 to 6,6 L2 to 4,4 L3 to 5,5 on the Delta run contactor
6,6 4,4 5,5 on the Wye start contactor also.
The phasing from the Main breaker to the motor leads connections has been
verified as correct for the Wye/Delta configuration.
The Main breaker is a 700Amp shunt trip breaker. It can be shunt tripped from the Overload relay or motor thermal sensors, as well as tripping from overcurrent. The adjustable trips are set at Maximum.
The starting sequence is:
The Wye start contactor is closed first.
The motor ramps up to speed in the correct rotation.
After 5 seconds the Wye start contactor opens and the Delta run contactor
immediately closes.
Wham! The breaker trips.
Why?





RE: Wye Delta Breaker Tripping Problem
RE: Wye Delta Breaker Tripping Problem
what is the instantaneous setting of the breaker?
setting should be selected just as high as if it was dol start imo
=====================================
(2B)+(2B)' ?
RE: Wye Delta Breaker Tripping Problem
You essentially have 3 viable options:
"Dear future generations: Please accept our apologies. We were rolling drunk on petroleum."
— Kilgore Trout (via Kurt Vonnegut)
For the best use of Eng-Tips, please click here -> FAQ731-376: Eng-Tips.com Forum Policies
RE: Wye Delta Breaker Tripping Problem
The reason is that the phase shift described by Jeff then changes from negative (or positive, you never know) to positive and if the shift you get with the actual connection is bad for the start, it is probable that the other shift helps.
I think it is worth a try. But, with 500 A, the cables may be a bit stiff and hard to change.
Gunnar Englund
www.gke.org
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.
RE: Wye Delta Breaker Tripping Problem
Gunnar Englund
www.gke.org
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.
RE: Wye Delta Breaker Tripping Problem
Article by Robert Wooddall that I often refer to, but the earlier links in the above are broken:
"Why Wye Delta Starting Cause Breakers to Trip"
The company that published that article, Master Controls, make Fire Pump controllers and breaker trips from transition spikes is, to put it mildly, HIGHLY undesirable on Fire Pump controllers. I used to be a Service Rep for them years ago. They taught me the conductor shift trick, it did work. They came up with a device called a "Leading Phase Monitor" that monitors the phase angles of the current and voltage and gave an LED indicator when it was OK, so we would shift the conductors to attain this. After they did that, they stopped telling everyone that there was a "free" fix to try first, because they wanted to sell their starters with that device built-in.
Instruction Sheet
"Dear future generations: Please accept our apologies. We were rolling drunk on petroleum."
— Kilgore Trout (via Kurt Vonnegut)
For the best use of Eng-Tips, please click here -> FAQ731-376: Eng-Tips.com Forum Policies
RE: Wye Delta Breaker Tripping Problem
Thanks for link and the education.
Dave