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In Line Contactor


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#1 lesl

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Posted 18 September 2010 - 01:01 AM

Hi:

Can a contactor be used between a VSD and motor? The reason is the VSD is controlled via a safety circuit on a light curtain. When activated the safety contactor drops out, and on resetting, the VSD takes 30 sec. The VSD does not have its own auxiliary power supply.

Any advice would be most welcome


LesL

#2 jOmega

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Posted 18 September 2010 - 09:40 AM

QUOTE (lesl @ Sep 17 2010, 08:01 PM) <{POST_SNAPBACK}>
Hi:

Can a contactor be used between a VSD and motor? The reason is the VSD is controlled via a safety circuit on a light curtain. When activated the safety contactor drops out, and on resetting, the VSD takes 30 sec. The VSD does not have its own auxiliary power supply.

Any advice would be most welcome


LesL



Opening of contacts between output of VFD and motor WHILE the VFD is supplying power to the motor can cause failure of the VFD output devices (IGBTs). and void the warranty.

Opening of contacts between output of VFD and motor AFTER the output has been placed in stop or standby mode ...i.e., all IGBTs turned off..... and then opening the contacts will usually not cause a problem.

Likewise, closing the contacts while supplying power can cause module failure or as a minimum, cause VFD to trip-off.

Contacts should only be closed when the modules are in their OFF state.

Using an interposing contactor between the VFD output and the motor, to STOP and/or START the motor, is not recommended because of the opportunity to cause failure of the IGBT modules.


Consult the manufacturer of the VFD for advice and recommendations.

#3 AB2005

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Posted 22 September 2010 - 07:35 AM

Which type/model of VSD you are using? There is also an Emergency Stop option in VSD which can be programed likewise. According to your requirement, if this would happen once or twice a day, you can control the input power of VSD through a contactor instead of output.

"Don't assume any thing, always check/ask and clear yourself".

#4 jOmega

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Posted 22 September 2010 - 07:27 PM

QUOTE (AB2005 @ Sep 22 2010, 01:35 AM) <{POST_SNAPBACK}>
Which type/model of VSD you are using? There is also an Emergency Stop option in VSD which can be programed likewise. According to your requirement, if this would happen once or twice a day, you can control the input power of VSD through a contactor instead of output.


Using an input contactor to cycle mains power to the VFD is not without concern.

There is a duty cycle that must be observed —i.e., how often the contactor can be cycled— else damage can be done to the precharge circuit with a possible risk to the bridge converter and the d-c bus capacitors; the mains fuses, or nuisance mains circuit breaker tripping.

The best source of information as to how often the mains power can be cycled is......... the VFD manufacturer.
(information often included in the instruction manual).




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