Response time of AC solenoid coil 2

[Sa-Ro]

Hi

How to measure response time of a AC solenoid coil in pneumatic valve.

We are testing response time for DC coils. Since there is straight line energizing and straight line dropping, we can easily measure the response time. With Tektronix MSO 4 series oscilloscope, automatic measurement is easily possible.

But, in AC coil, sine wave is applied to coil. Which is the start point for measurement in raising and falling edge.

If we are applying 100 ms duration, from sine wave start to end is more than 100 ms. AC voltage at trigger point is varying as the sine wave varies.

How to make automatic measurement in oscilloscope?

Thank you.

 

[waross]

Measure the current.
The current will be higher until the solenoid closes.

If we are applying 100 ms duration, from sine wave start to end is more than 100 ms.

At 50 Hz the period is 20 ms.
Are you using less than 10 Hz?

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[Sa-Ro]

Yes.

ON time: 50 ms,
OFF time: 700 ms

It is a pneumatic valve.

Hence as soon as the solenoid operate, the air output will be measured by pressure transducer and convert as DC volt.

From trigger point (AC) to this DC (pressure transducer) volt is target measurement.

 

[BrianE22]

Use a zero crossing triac or solid state relay. They don't start conducting until the sine wave is close to zero volts although I don't know what the variance is on starting points.

 

[waross]

If we are applying 100 ms duration, from sine wave start to end is more than 100 ms.

ON time: 50 ms,

50 ms on time may be a little short for a valid test.
What are you trying to accomplish?
PWM of an air supply?

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[itsmoked]

Current drop and use a zero crossing Solid State Relay for consistency.

Both are good suggestions.

If you're trying to put these numbers in a data sheet then you will need to specify how you measure it. Otherwise the operating time of an AC solenoid is going to vary by half of the AC period at the specified frequency randomly based on when the energisation occurs in the cycle.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[waross]

It is a little confusing when you ask for the operating time of the solenoid when you are measuring the combined response time of both the solenoid and the valve.
The response time of the solenoid is basically over before the response time of the valve starts.
Consider the following:
Simple test: (The operating time of the solenoid at 50 Hz plus 0 to 5 ms) plus (the time for the air pressure to reach 63% of the target value x 5)
More advanced: Use a zero crossing relay, being sure to start timing when the relay starts to conduct, not when a trigger is applied to the relay.
However you measure, the 0 to 5 ms delay may be a factor in the real world.

Again. WHY?

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[waross]

If the exact operating time is that critical to your application, use DC.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[Sa-Ro]

I am using the following equipments:

Power source: GWInstek - 2100 - We can set the starting and ending phase of AC sine wave. I had set to 0.

Tektronix MSO 4 series to capture the waveform.

Keller make pressure transducer to measure the output pressure.

The valve can operate and the 90% (of inlet pressure) of air output is reached at pressure transducer within 30 ms itself.

Hence I am using 50 ms ON time.

700 ms OFF time is based on the oscilloscope waveform update rate at 20 ms horizontal scale.

I am trying to measure,

1) how fast the 90% of air output can reach from the trigger ON - AC zero crossing.

2) how fast the 90% of air output can drop from the trigger OFF - AC zero crossing.

We are having DC model also. Some customer asking for AC model.

Response time measurement at DC is our regular work.

 

[waross]

Your customers may not have the luxury of a zero degree starting wave form.
If I was using your valve I would like to see the spec list the operating time as, for example:
Operating time to 90% output pressure: 50 ms plus 0 to 8 ms.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[waross]

You may use itsmoked's suggestion:
"Use a zero crossing Solid State Relay for consistency."
Then for real world conditions, report the operating time as:
0 to 8.3 ms plus 50 ms.
A subtle difference.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[waross]

Be aware that the DC model may be cycled continuously as fast as desired.
A fast duty cycle on an AC solenoid may cause overheating.
An AC solenoid will have an initial current surge on energization.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[Sa-Ro]

ok. Thank you.

For example,
If the valve triggers at 0 degree, then 90% output may be 45 ms

If the valve triggers at 45 degree, then 90% output may be 40 ms

If the valve triggers at 90 degree, then 90% output may be 35 ms

Am I right?

As per ISO 12238:2001, the trigger point to be set to zero crossing point for A.C response time measurement.

 

[itsmoked]

Yes, like that but it needs to be measured.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[Sa-Ro]

OK. Thank you.