Wrong voltage on solenoids

[PhaseShift]

We have recently had some wrong solenoids ordered that are a different voltage rating then our control voltage of 120V AC. I was curious what would happen in the following two cases:

What if we put 120V on a solenoid that is rated for 180V AC? Would the solenoid work? Would it draw more current? Would it burn up?

Similaraly, what would happen if we put 120V AC on a solenoid rated for 24V AC?

 

[zog]

They all have minimum and maximum pick up or drop out specs, likely you will be outside those specs.

 

[mcclary's electrical]

We have recently had some wrong solenoids ordered that are a different voltage rating then our control voltage of 120V AC. I was curious what would happen in the following two cases:

What if we put 120V on a solenoid that is rated for 180V AC? Would the solenoid work? Would it draw more current? Would it burn up?

Similaraly, what would happen if we put 120V AC on a solenoid rated for 24V AC?

I once saw an entire MCC come from the factory with the wrong coils in all the starter buckets. Nodody caught it. They were 120 volt coils and got hooked to 277 volt. No of them faired well:grin:,,,or ever worked again

 

[PhaseShift]

They all have minimum and maximum pick up or drop out specs, likely you will be outside those specs.

Thanks. I guess I'm looking for a more theoretical answer as to what will happen in these 2 cases?

 

[zog]

Thanks. I guess I'm looking for a more theoretical answer as to what will happen in these 2 cases?

How about some more details on the solenoids you are asking about? There are many different types with different tolerances. Safe to say you will fry the 24V one with 120V, the 180V one will likely not work depending on the tollerances.

 

[ggunn]

Thanks. I guess I'm looking for a more theoretical answer as to what will happen in these 2 cases?

To the question "what would happen if we put 120V AC on a solenoid rated for 24V AC?," I think the technical term for the answer is "blooey". :grin:

 

[LarryFine]

What if we put 120V on a solenoid that is rated for 180V AC?

Most likely it will have difficulty pulling in, and be unreliable.

Similaraly, what would happen if we put 120V AC on a solenoid rated for 24V AC?

That's a no-brainer; it'll let the magic smoke out. . . . once.

 

[don_resqcapt19]

But if you put 120 ac on a solenoid made for 24 dc, it will last about a year...at least the couple that I did that to lasted that long. They seemed to be running hot, but when you look at the technical information from this company, they say that it is not too hot unless it is smoking.

 

[PhaseShift]

Most likely it will have difficulty pulling in, and be unreliable.

Why is this? Would the coil have a higher impedance value?

That's a no-brainer; it'll let the magic smoke out. . . . once.

Is this because it is not insulated for 120V or the V/Hz ratio at 120V will overflux the coil and put it into extreme saturation?

 

[PhaseShift]

But if you put 120 ac on a solenoid made for 24 dc, it will last about a year...at least the couple that I did that to lasted that long. They seemed to be running hot, but when you look at the technical information from this company, they say that it is not too hot unless it is smoking.

I know that when comparing an AC and DC coil of the same voltage the AC supply voltage would have difficulty pulling in the DC coil, because the DC coil would have more resitance than an AC coil. (No reactance with DC)

But I guess because the 24V coil is so much smaller the resistance is smaller, and therefore the 120V can pull it in?

 

[PhaseShift]

If a solenoid has a kw rating, can we calculate the current by dividing this kW rating by the voltage? Or can you not perform this calculation, because the solenoid will have a reactive current as well and in order to determine current you need to know the total kVA of solenoid?

Will a solenoid have a power factor as a motor does?

 

[gar]

100420-2300 EST

PhaseShift:

DC solenoids do not have a shaded core. Thus, buzz like mad on AC.

A relay of the same model number made for DC operation will have a higher resistance coil than the AC model where both are of the same voltage rating.

Inductance in the coil of a DC unit only affects closing and opening time of a relay (read that as the same as solenoid from a broad point of view).

In an AC unit before the armature closes the coil inductance is lower than when closed. Thus, initially there is more current and then this drops to a lower value. This is an advantage of the use of AC vs DC. However, an air valve with a DC coil will not fail if the valve spool fails to move, but an AC version will fail.

Your solenoid with half voltage applied will probably fail to close. If closed it might stay closed. In some post somewhere on this site I provided measurements on an AB #2 starter.

If you apply excessive voltage the current will be high and the coil will burn out as everyone above has said.

.

 

[LarryFine]

Why is this? Would the coil have a higher impedance value?

Of course. Being rated for a higher voltage means having a higher impedance, resulting in a lower current, all of which is required to obtain a given power, which is what gets work done.

Is this because it is not insulated for 120V or the V/Hz ratio at 120V will overflux the coil and put it into extreme saturation?

The latter. Plain ol' Ohm's Law. Too much current for the impedance to limit it to the wire's ampacity. Heat destroys insulation, allows shorts and more current; wire itself eventually melts.

 

[PhaseShift]

Of course. Being rated for a higher voltage means having a higher impedance, resulting in a lower current, all of which is required to obtain a given power, which is what gets work done.

The latter. Plain ol' Ohm's Law. Too much current for the impedance to limit it to the wire's ampacity. Heat destroys insulation, allows shorts and more current; wire itself eventually melts.

Yes but isn't a coil similar to a transformer or motor whereas it cant necessarily be viewd as a constant impedance becasue it is always striving to maintain the same power.

Plus as mentioned when the solenoid pulls in the device the reactance will change and thus the total impedance will change as well.

Are you saying that the increased current is simply due to less reistance on a lower voltage rated coil?

How about my question in determining current off of coils wattage rating?

 

[LarryFine]

Are you saying that the increased current is simply due to less reistance on a lower voltage rated coil?

Yes, at extremes beyond a motor or solenoid's voltage range, simple voltage-through-resistance will overtake the device's attempt at maintaining constant power.

 

[PhaseShift]

Yes, at extremes beyond a motor or solenoid's voltage range, simple voltage-through-resistance will overtake the device's attempt at maintaining constant power.

What about for not so extreme cases such as 120v on a Solenoid rated for 180V?

 

[gar]

100421-1517 EST

PhaseShift:

For a DC solenoid or relay any voltage below its rate value can be applied continuously without damage to the coil. Below some voltage the device will not pull-in and therefore your intended function fails.

For an AC solenoid or relay there is some voltage below which the device will not put-in. Below this point and above some lower voltage it is possible the coil will burn out. Typical on solenoid valves where the spool gets stuck, but this is with full voltage applied.

.

 

[LarryFine]

What about for not so extreme cases such as 120v on a Solenoid rated for 180V?

I'd expect the pull-in power to be weak, and the less-than-designed voltage may be low enough to not overheat the empty coil.

Added: Or, what Gar said.

You can always try one and let us know what happens. That beats speculation.

 

[a.bisnath]

differences in ac and dc coil construction

differences in ac and dc coil construction

been there but never successfully done that ,a dc coil with ac voltage will not pull in it will hum vibrate and create heat coils can be rewound done this did work the book 'ELECTRICAL MOTOR CONTROLS' BY Gary Rockis and Glen Mazur in chapter 5 explains it well