Inverter Stopping

[Rheinhardt]

Hi guys,

I would like your opinion on the following.

We have a motor schematic where we cater for a 0.55 kw Variable Speed drive.

The system contains the following :
3-Phase feeding Overload/Contactor system
Contactor feeding SEW Movitrac 7 Inverter.
Inverter feeding Motor

Question :
Our safety system is connected to the Output card that enables the contactor and Inverter
When an e-stop is hit the contactor falls out and the 3 phase on top of the Inverter falls away while the drive is active and running.

What is your opinion on this , I see it as bad practise as the inverter has got its own enable signal that we can disable.

Question 2:

Can you damage the inverter by doing this??

Any opinions will help

Kind Regards

Rheinhardt

 

[Skogsgurra]

Yes, you are right. It is bad practice. You should disable first. Or use the normal stop circuit and let the inverter controll the contactor - if there is an output for that.

On the other hand, the motor is quite small and the energies involved seldom destroy anything. Also, the inverter gets its auxiliary supply from the DC link and cutting out the mains supply is usually OK and leads to a more or less controlled stop. Inverters are built to withstand an occasional black-out. I do not think that you will damage it.

Gunnar Englund

http://www.gke.org

 

[OperaHouse]

You are right, the caps can store enough energy to run a motor under low load for a couple of seconds. Some inverters have connections to these caps for external brakes. Connecting an additional relay with a low value resistor to drain off this charge at drop out will help. Unfortunantly, this is DC and relays that can handle this switched voltage are expensive.

 

[laundry]

HI
WITH REGARDS TO YOUR INVERTER ONLY NEW GENERATION DRIVES ARE ABLE TO BE CONNECTED STREIGHT FROM THE MAINS AS THESE HAVE BUILT IN PROTECTION AND MONITORING OF POTENTAL FAULTS.
YOUR DRIVE MUST HAVE AN IN LINE CONTACTOR TO ISOLATE IT FROM THE MAINS IN AN EMERGENCY.IF YOU ARE CONSERNED ABOUT THE OVER RUN THEN I WOULD FIT A SMALL ELECTRO MECHANICAL BRAKE I HAVE IN THE PAST HAD INVERTERS RUN WITH NO ENABLE ON BECAUSE OF AFAULT ON THE PCB, VERY RARE BUT THIS WHY.

 

[Skogsgurra]

Hi laundry,

I notice that you are a relative newcomer to the site. We prefer not to use the Caps Lock in here. Makes your messages easier to read.

Gunnar Englund

http://www.gke.org

 

[mil3]

Modern drives of today is well protected to not damage when incoming power system fails or gets occasional brown-outs.
I have however seen one installations where the drives system start/stop is connected through an incoming contactor and to the digital inputs. The customer had drive failures every 3-6 months for 2 years and decided to call us in to review the installation for an unbiased opinion. Dropping out power too frequent (especially as a start/stop mechanism) will result in damage over time due to the precharge circuitry duty cycle being exceeded. Just ensure if you do use this practice(which you should rather not)to ensure it is for "Emergencies" only and not a start/stop mechanism.