220 vac motorized linear actuator sometimes goes wrong way

[RickOzone]

We have a linear actuator which operates with a 220 vac bidirectional motor. When one coil is energized the motor turns one way. When the other coil is energized the motor turns the other way. However, sometimes the motor spins slower in the wrong direction. Any ideas on how to prevent this from happening.

 

[DougMSOE]

What is the HP? Are you willing to change motors?

 

[jbartos]

Suggestion: There may be a flaw in the controls. Contact tech support to address it.

 

[RickOzone]

The motor is small and draws 10.5 VA according to the name plate on the actuator. The actuator is installed on a valve. The power for the motor was supplied via an up down switch. Therefore, the wrong direction could not be caused by the controls. We can not change the motor but the manufacturer could. I have seen this problem before on another device and the problem was never solved. I was hoping for some insight into what the cause and cure might be.

Thanks

 

[jbartos]

Suggestion: Even if it is caused by the motor turning in wrong direction, e.g. the motor might potentially turn in a different direction on its input powering, then still it is the motor control flaw that permits that. The control should not be applied to such motor that can turn in an upredictable direction of rotation.

 

[nbucska]

Can you describe the motor in some detail ? Who made
the control circuit ?


<nbucska@pcperipherals.com>

 

[RickOzone]

The motor is about 2&quot; diameter and 2&quot; deep. It is 500 rpm 50 Hz. We are testing it on 60 Hz. It has three wires coming out of it. One wire is the common or neutral connection. One of the wires, when energized makes the motor turn in one direction. The other wire makes it turn the other way. The three wires connect to a circuit board which has a capacitor connected between the two windings (0.22 uF). The motor is marked with 50 Hz 0.27 uF. There is a resistor in series with each of the windings 1k5 about 5 Watts. There is also a small RC snubber from each of the windings to the common neutral connection. That's all of the control circuitry.

 

[jbartos]

Suggestion: The motor application, including the circuits and component values, should be analyzed for the proper design and correct functions of components. Probably, the easiest way to solve it is to contact the motor application engineer/designer. The analysis will require the motor all motor electrical data required by the analysis, e.g. winding impedances, motor type, internal connection, etc.

 

[CarlPugh]

I think this type motor is called a permanent split capacitor motor. We used to use them and there are two types of this type motor. One type is called reversible while running and the other type is called not reversible for while running.
If you use a motor that is not reversible while running, it may continue running in the same direction if an attempt is made to reverse it while it is running.
There are two solutions to your problem, the first is to let the motor come to a complete stop before trying to reverse it.
The second is to use a motor that is reversible while running.
Also it may be possible to correct this problem by using a capacitor with different capacitance? The motor manufacture should be able to tell you if it is practical to change capacitor value.

 

[SERVOCAM]

Almost sounds like an AC Synchronous....3 wires, 1 common neutral, swtiching between other 2 phases to change direction, capacitor & resistors...but the 500 rpm sounds high for this type. I have only seen 200 rpm & 72 rpm AC Sync.

 

[RickOzone]

Sometimes when the motor goes backwards, it changes direction without interrupting the power to go in the correct direction. Note that when it is going the wrong way, it turns at a slower speed than normal, perhaps 1/4 to 1/2 the normal speed. It is also noisier. This causes a problem with the controller which is trying to increase the flow and the feedback shows the flow decreasing. We have contacted the local representative about the problem. They don't have an answer, so they are intending to send it back to Germany for repair or replacement. However this option may be a problem for our client due to the time. I'd like to try changing the capacitor if someone could tell that is likely to work. At the moment the actuator is in the hands of the representative.

 

[EnergyEngineer]

The 16 or 18 bit pic mounted onto the control is fried, hence the automatic phasing no longer functions. It can go either direction dependant upon the position it is laid at rest before power is energized.

 

[jag27]

if it is a linear actuator , do you have pos,neg limits on the motor/actuator?

 

[EdDanzer]

Maybe you have an overrunning load so when you try to start the motor it does not have enough torque and the load actually starts to rotate the motor backwards out of phase.