single coil latch type relay driven with AC?

[neazoi]

Hello, I was wondering if a single coil latch type relay (changes state by changing coil polarity) can be driven with AC 50Hz so that it can change state 50 times per second?

Also do these types of relays have some kind of semiconductor inside or are they semocinductor-free?

 

[KlausST]

Hi,

they are semiconductor free.

If you run such a relay with AC then it depends on the speed of the relay. Some are fast enough to with within 20ms.
Like very often. The datasheet will tell you.

Klaus

 

[BradtheRad]

I once tried to switch a relay on-and-off many times a second, simply by sending pulsed DC to the coil. It worked, although I don't believe it worked as fast as 60 Hz.

As I understand it, a latching relay does not change state when power is disconnected. Therefore it is useful in roles where you don't want to waste current keeping it on for a long time.

 

[neazoi]

I once tried to switch a relay on-and-off many times a second, simply by sending pulsed DC to the coil. It worked, although I don't believe it worked as fast as 60 Hz.

As I understand it, a latching relay does not change state when power is disconnected. Therefore it is useful in roles where you don't want to waste current keeping it on for a long time.

I think that any relay can switch 50 times per second, even some old and bulky relays I have can self oscillate when connected appropriately and the sound that comes out of them is about 100Hz or so.
The point it, will the AC be able to directly switch the relay (these relays toggle by switching the polarity of the coil)

 

[neazoi]

grounding the secondary of AC transformer?

Hi, this design is a mechanical mains rectifier using a single coil latching relay.
These relays switch on/off by alternating their coil polarity.

I am considered in the GND point of the secondary of the transformer.
Will this specific relay be driven that way?

 

[Audioguru]

Re: grounding the secondary of AC transformer?

I think your relay will wear out soon. Why don't you use an electronic rectifier that might last forever?

 

[neazoi]

Re: grounding the secondary of AC transformer?

I think your relay will wear out soon. Why don't you use an electronic rectifier that might last forever?

I know that
The question was about the relay, if it can be driven that way.
I do not know many things about transformers but if I ground one end of the secondary, what kind of waveform will appear to the other with respect to the ground? A sinewave with positive tops and negative (below ground) bottoms?

If that is the case then the relay coil will see an alternating polarity, even if one of it's coil ends is connected to gnd.

 

[FvM]

Re: grounding the secondary of AC transformer?

You are asking two unrelated questions in one.

Grounding the transformer doesn change the circuit behaviour at all.

If the polarized relay does work with 50 Hz AC drive voltage depends on the relay specification and can't be answered by looking at the schematic. But very clearly, the relay contact shorts the transformer output with a capacitor, it will most likely weld immediately and cause the primary fuse (if any) to trip.

 

[D.A.(Tony)Stewart]

AC type Relays use a shaded pole type magnetic coupling much like AC motors with shaded poles, so the force is smoother. within the full cycle.

But certain AC solenoids running off single diode rectified line AC can move fast enough to act as a spring resonant water pump. THis is what is used in Expresso machines for cold water with a plastic pressure valve to act as a diode for water flow.

• Shaded pole AC relays are generally constructed like simple DC electromagnetic relays with a portion of the core pole face separated from the rest of the pole face and enclosed in a loop of copper.
• This loop produces a lag in the timing of the ac magnetic flux in one portion of the pole face with respect to that in the unshaded portion.
• While the current in the coil passes through zero twice each cycle, the flux in the armature gap remains at a high enough level to hold the armature operated. If the minimum pull exceeds the mechanical forces (spring and gravity) tending to restore the armature to its de-energized position, there will be little, or no buzzing, of the armature or contact chatter.
• The current drawn by a shaded pole relay is determined by the ac impedance of the coil at the power line frequency.
• This impedance depends upon the coil constants, the characteristics of the magnetic circuit, and the armature position.
• For example, the impedance of a relay may be twice as large with the armature operated (seated) as with it de-energized.
• It is customary to express the sensitivity or actual power required of such an ac relay in volt-amperes, but the degree to which the iron is magnetized is better measured by E^2/Ro the ratio of the square of the applied voltage to the coil resistance for a full coil.
• The degree of magnetization determines the inductance and impedance for any particular frequency at various applied voltages.
• From the applied voltage and impedance, the actual volt-amperes can be determined.
• Some relays will not remain energized or may chatter badly if the coil current is reduced to half of the rated pick-up value.
• Many ac relays are intended to be energized at the rated voltage value even though there may be considerable margin between pick-up voltage and rated voltage.
• This is sometimes referred to as on-off operation, or per the IEC notation of an "all or nothing" relay.

Ref **broken link removed**