Phase Control
- Thread starter jcslayton
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hbiss
EC, New York NEC: 2017
- Location
- Little Falls, New York NEC: 2017
- Occupation
- EC
Re: Phase Control
I think you are going to have to do alot of elaborating. Maybe it's just me but I have no idea what an environmental control unit is, why it would need a phase control or anything about the private sector.
I'll take a stab though and guess you are talking about military vs commercial aircraft?
I think you are going to have to do alot of elaborating. Maybe it's just me but I have no idea what an environmental control unit is, why it would need a phase control or anything about the private sector.
I'll take a stab though and guess you are talking about military vs commercial aircraft?
- Location
- Massachusetts
Re: Phase Control
OK I will guess a phase monitor on HVAC equipment.
If that is it, I would say only on the better quality units.
OK I will guess a phase monitor on HVAC equipment.
If that is it, I would say only on the better quality units.
brian john
Senior Member
- Location
- Kilmarnock, Va
- Occupation
- Retired after 52 years in the trade.
Re: Phase Control
I go for the phase relay
Only if you are concerned enough to order the option from the factory.
I go for the phase relay
Only if you are concerned enough to order the option from the factory.
Re: Phase Control
Large motors have phase failure relays to prevent the motor from continuing to run during a single phase condition.
Motors that are not under the single phase mode will supply the lost phase to the affected motor at a reduced voltage, causing it to burn without tripping the heater relays.
Large motors have phase failure relays to prevent the motor from continuing to run during a single phase condition.
Motors that are not under the single phase mode will supply the lost phase to the affected motor at a reduced voltage, causing it to burn without tripping the heater relays.
Re: Phase Control
I should have been more detailed in my reply. My thinking is a lot faster than my typing.
I should have stated; on systems with large and small motors, during a single phase incident on the power grid, the large motors will generate the faulted phase and cause the smaller motors to run at reduced voltage on one phase. This burns out the small motors by creating a layer to layer fault(shorted turn). This phase does not pull enough current to dump the overload relay, but creates a hot spot in the winding.
A phase failure relay dumps all magnetic starters during the loss of one phase.
I should have been more detailed in my reply. My thinking is a lot faster than my typing.
I should have stated; on systems with large and small motors, during a single phase incident on the power grid, the large motors will generate the faulted phase and cause the smaller motors to run at reduced voltage on one phase. This burns out the small motors by creating a layer to layer fault(shorted turn). This phase does not pull enough current to dump the overload relay, but creates a hot spot in the winding.
A phase failure relay dumps all magnetic starters during the loss of one phase.
jim martin
Member
Re: Phase Control
I find it cheap insurance on the pump control panels I build. Time Mark makes a relay (#2522 I think) that costs less than $100 that will drop out if you loose a phase. Much cheaper than rebuilding a pump.
I find it cheap insurance on the pump control panels I build. Time Mark makes a relay (#2522 I think) that costs less than $100 that will drop out if you loose a phase. Much cheaper than rebuilding a pump.
- Location
- Bremerton, Washington
- Occupation
- Master Electrician
Re: Phase Control
Protecting a motor with a phase montitor is commonly done, especially on more expensive motors. I always use a phase monitor on submersible motors. I have seen pump stations loose a phase, but the lights would still work, for the operator, its not clear why the pump does not run as the "lights work". I wire a white LED pilot light to the phase monitor, label it CONTROL POWER NORMALLY ON.
A three phase motor may run when single phased, depending the load, with one phase lost, only 57% normal load can be driven, so lightly loaded motors will run.
However, an IEC motor over will offer much better protection from single phasing as the overloads have a differential trip mechanism, such that when a phase is lost, the other two overloads are more responsive to motor current - the motor will draw more current when the phase is lost.
Remember when a phase is lost, the motor will regenerate the missing phase, its hard to find this with a voltmeter, as the voltage will be there, but be off a bit. the only way to know for sure is to deenergize and check incomning power, or use a phase rotation meter.
Protecting a motor with a phase montitor is commonly done, especially on more expensive motors. I always use a phase monitor on submersible motors. I have seen pump stations loose a phase, but the lights would still work, for the operator, its not clear why the pump does not run as the "lights work". I wire a white LED pilot light to the phase monitor, label it CONTROL POWER NORMALLY ON.
A three phase motor may run when single phased, depending the load, with one phase lost, only 57% normal load can be driven, so lightly loaded motors will run.
However, an IEC motor over will offer much better protection from single phasing as the overloads have a differential trip mechanism, such that when a phase is lost, the other two overloads are more responsive to motor current - the motor will draw more current when the phase is lost.
Remember when a phase is lost, the motor will regenerate the missing phase, its hard to find this with a voltmeter, as the voltage will be there, but be off a bit. the only way to know for sure is to deenergize and check incomning power, or use a phase rotation meter.
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