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If the motor is required to accelerate from 0% to 30% speed in 1s (mentioned in the original post), it may be possible that the VSD requires a 300% overload. Acceleration time is dependant on acceleration torque (VSD current) and system inertia. It is also interesting to note that there will...

DanThomas; Adding an extra overload would not prevent your motor from failing. However, your Overload relay was not set correctly to begin with! It must be set to 37 amps. As GGOSS stated previously, the O/L may not have differential protection - which would not protect against...

A Variable Speed Drive (VSD) will provide the most amount of torque per amp of any motor starting method available. If you choose a reputable supplier (of both motor and VSD), reliability will be much better than the WRM option. An added bonus is that you will get full speed control.

BRIS; I would suggest using outlet damping as a viable alternative in this situation. It will save you dollars (just not as much as VFD) and is easily maintainable.

There are two components of motor current: 1. Flux or magnetising current 2. Torque producing current Torque producing current is in phase with the voltage (resistive), while flux current lags the voltage (inductive). I would suggest using one of the digital outputs to "At Torque&quot...

You may also want to try a company in the US called Anorad: http://www.anorad.com

As far as I can tell, there are two issues for emergency stopping: 1. Electrical isolation 2. Motion isolation 1. Electrical isolation can be achieved by an isolation contactor. An isolation contactor on the output side of the VSD is more effective than one on the input. The reason for...

To add further to marke's comments, the input power factor to a VSD is proportional to load. The PF of the VSD is constant, but as the input current increases (due to motor current) the waveform becomes increasingly distorted (harmonics). It is therfore impossible for a VSD manufacturer to...

As vanstoja points out in the above post, RTD's used by themselves do not provide adequate protection of motor windings. When used in conjuction with a motor overload, the RTD's certainly have merit. The main advantage is that the RTD's are embedded in the windings and are therefore affected...

Try thread237-7851

A contactor on the input of the drive will not serve as an emergency stop. Depending on the loading of the motor, the bus capacitors may keep the bus voltage up to a level that will still provide power to the motor, after the input power is removed. If the load requires emergency stopping...

qvo; Dependant on your local regulations, an IC may not be required. They do, however, provide many advantages: 1. True off state isolation. 2. Dis-connection from the line during non-operation. 3. Means of fault current breaking on solid state component failure. As for your second...

My $0.02 I have heard of applications that could not be started across-the-line, being started by a SLV (sensorless vector) VSD. A VSD attempts to use only the "steep" part of the motor torque Vs speed curve ie. near full speed. If the acceleration rate on the VSD is set to short...

DayEng; It depends on what you are trying to acheive or prevent. Reactors or chokes are used on the output side of a VSD for a number of reasons. Firstly, the choke will reduce the rate of dV/dt and reduce the effects of cable charging current. It will also be assist in...

Good explanation Mark. I'll throw in my $0.02... Another point is that the wye-delta is usually a timed based transition. Therefore, the speed at which the transition occurs will vary depending on the loading of the motor, mechanical wear and even supply voltage fluctuations. It is therefore...

Purplepete; Can you please post this "algorithm" used to work out the PFC kVAr. It seems as though your correction may be a little on the high side (possibly creating a leading PF).

electricuwe; The new AB unit actually uses SGCTs with a PWM-CSI topology. The parts count is greatly reduced (compared to multi-level PWM-VSI topology) and the SGCTs have double sided cooling (which IGBTs don't). When using a 6-pulse or 12-pulse MV drive, you typically need a high impedence...

Electricuwe; Yes the suggestion of an AFE is an easy one, because it will work! An AFE will be more expensive (I think you will be suprised by how little it adds to the total price), but you will not have to oversize the Alternator nor worry about AVR response (harmonics). The two main...

Redtrumpet, I'm sure that there are quite a few manufacturers (I only know of two): Allen Bradley Bulletin 140 Schneider (Telemecanique) GVN

I think the best solution would be a motor protection circuit breaker. These provide both adjustable thermal and magnetic release, and are designed specifically for this type of application. jbartos, A circuit breaker alone cannot provide adequate protection for a motor. If you look at the...