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The prime application for the soft starter, and in many cases variable frequency drives on fixed speed applications, is to get the driven load up to full speed to enable it to do some real work. This focus on energy saving by soft starters and VFDs creates a lot of confusion and miss-information.

Soft starters do sometimes include an energy saving algorithm which is designed to reduce the voltage applied to the motor when the motor loa ...

Every motor is to be protected with back up MCB / fuse and overload and single phasing protection. The motor is to be earthed properly. Once protective relays are connected in the system the system get tripped when the live terminal of any phase get earthed. Once tripping happens proper Megger check to be carried out for cable and Motor, to find the cause of tripping. The tripping can be due to Earth fault.

First, the motor body should have a "hard" connection to ground to keep the ...

This question is for developer or those who are master in PID control & would like to save cost in certain application. For speed control, it's no longer used PID methodology by programmer. Now PID control is integrated into variable frequency drive control. For example, if you want to stabilize the speed at 1500rpm, no matter load changed, via an advanced VFD, PID is itself tuning to keep it stable at 1500rpm.

I like the auto tuning function on rotating equipment that has hig ...

Q: I have a conveyor application. There we have a Motor connected to Gear Box. Motor is driven by a variable frequency drive (VFD). Details are as follows
Motor Power - 2.2 kW, 415V, 50 Hz, 1460RPM
VFD - 2.2 kW
Gear Box - Ratio = 58.25, RPM - 25 Rev/Min ,

According to the Above details, gear box output is 25 Rev/Min When the Motor Runs at 50 Hz at 1460 RPM. But I need to increase the Gear box output (Conveyor Speed) from 25 RPM to 53 RPM. So, as a t ...

All AC machines (synchronous and induction) have a window of opportunity for reclosing. The basic resolution for reclosure (also known as "bus transfer") is either "fast" or "slow".

Typically, "fast" reclosure efforts occur within a few cycles (think less than 8, and often less than 6). In terms of actual time elapsed, it will certainly be faster than 0.12 seconds. If you're attempting this on a synchronous machine, it MUST have brushless excitation, since it can only be done with ...

VFD derating is a manufacturer requirement when equipment ambient temperature is above 40 C degrees OR when equipment site is above 3000 feet in altitude. It is clear for manufacturers and engineers to avoid temperature derating by having the VFD's ambient temperature not to exceed 40 C degrees. On the other hand, VFD's manufacturers claim on altitude derating is due to thinner air at higher altitude that compromises the heat dissipation from the electronics. Although, it is a real claim, man ...

Why voltage in some countries is 220V (208V, 230V, 240V) and 110V (100V, 120V) in some countries? Why can't we have the same Voltage and what are the Pros & Cons of using 110 V or 220 V in their Respective regions?

110V or 220V, Each system has its own advantages and disadvantages, so each country before designing a system Engineers sat down agreed on factors and concluded on which system to use taking in account:
Their ...

There is a type of constant current load, once used for street lighting. Going back in time when electric utilities first started providing street lighting, there was a system that wired the luminaires in series instead of parallel. Each luminaire had a transformer wired in series with the hot leg, and the low side was connected to the bulb. Since the bulbs, all identical, were effectively connected in series, the current delivered to the circuit was a constant regardless of the number of bul ...

Over speeding the motor with a variable frequency drive will depend a lot on the existing load on the motor. If it is a fan load and you are currently at 100% of NP rating, you have no head room left to play with. If you have a roll spinning lightly loaded you will have much more head room. In some applications we run 240vac motors on a 480vac VFD and over speed from 60 Hz rated to 90 Hz- and develop 1.5 x the HP at rated torque. If you have a 480vac ...

There are two things to consider when looking at increasing the shaft speed of a motor (by whatever method).

First: mechanical. Can integrity of rotor design be maintained? (Typical max safe speed is NP * 1.25 which does NOT mean it operate at that speed, but only that it will not come apart and cause injury.) Will bearing and/or lubrication handle the increased speed? (There's going to be more heat.) How about vibration? (Typically, faster speeds require smoother operation to prev ...

SYNCHRONOUS: means "turns at a speed proportional to applied frequency independent of load".

For this to occur, the magnetic field on the rotor must be powered separately from the stator magnetic field. As Hector pointed out - the rotor field may result from permanent (e.g. rare earth) magnets, or from an electromagnet.

If the rotor field is electrically created, the current has to come from somewhere. One way to do this is to use a separate DC supply and supply power th ...

Is there any problem in conducting dynamic balancing of rotor with lower rpm than the rated rpm of the machine? For e.g. for a 3000 rpm motor rotor if we are doing the dynamic balancing @ 750 rpm will it create any vibrational problems. If it is so what is the acceptable speed limit for doing the dynamic balance of 3000 rpm rated motor rotor.

As a minimum, the equipment really should be balanced at operating speed. The "acceptable" capability limit of the facility performing dynami ...

There is more than three protections methods for this case.
1-You can use overload with phase failure detection function this device monitor the current at the three phases if there is no current at one phase the device stop the motor.
2-You can use a sensitive phase failure relay with unbalance detection function and adjust the action time to 0.1 second and the rate of unbalance to less than 5% when one phase loss a high current pass through the other two phases that make drop down ...

I have two generators 125kW that when they are in parallel and the power is perfectly shared with 60+60kW @PF=1 (resist load) I have 10Amps on neutral. When I unbalance the load (I want remove from grid one Generator) I saw current over 100Amps on neutral, and when the generator is close to have 0kW, current on neutral is over 300Amp.
What's the cause of this problem?

If you have 10kVAR, you have reactive power. Circulating currents have nothing to do with load power factor. Is t ...

We have done several years of research on recycling rotating electric machines. We have tried to identify new guidance on this matter. We conclude:
1. There are cases where a rewound motor is better than a new one. We have the opportunity to design the winding tuned to the application. The result in this case might be an upgraded motor.
2. The biggest problem we identify in our research has been mentioned by several discussions. The magnetic core might suffer degradation during repa ...

Q:

I have a trouble with a Siemens Micro-master 440 AC converter equipped with the encoder module. Sometimes, not regularly, the axis stuck giving the fault F090 (encoder loss) but everything seems to be OK. I've checked cables, connections, encoder, increased the thresholds and so on, but the problem still appears. Anyone have kind of experience with such trouble?

A:
If has been working for years, it must to be a hardware problem. I would suggest the following:
* al ...

The power plant project is 163MW CCPP and the owner want to select Generator Converter vector group between YNd11 & YNd1. Which vector group should be chosen?

The following will tell you the suggestions with reasons.

Basically this vector group arrangement will define the physical displacement of the generator shaft and the electrical phase of the network. Both solutions can work, the decision depends on the environment in which the generator and the converte will work. I ...

How can I control through the VFD Torque for a motor as I have a pump motor of 110 KW of rated current 200A controlled by Soft Starter and during the actual operation it consumed only 65 KW with 98A so I want to change this motor with another one lower in KW with VFD to control at the new motor Torque, so how to do that?
If the new motor is large enough to provide the load requirements then reducing the motor size will not affect performance. It is the load that dictates torque required ...

More specifically, a low voltage (LV) motor is normally <1000 V or <600 V, depending on who you ask. They are usually wound with round enamel-covered wire. This is called random-wound or mush-wound coils. Medium voltage (MV) motors, with voltages up to 13.8 kV or even higher, are wound with rectangular cross-section copper wire with enamel or mica tape insulation, depending on the voltage level. This is known as form-wound coils.

Because form-wound coils must be individually ...

During a discussion with a colleague, I came to know that for motors with antifriction bearings, you only need one accelerometer to measure the vibrations, whereas for motors with sleeve bearings two accelerometers are needed (one for measurement in X direction and other for measurement in Y direction).

ALL bearings are "anti-friction", otherwise they would not be bearings.

There are basically two types of bearing: non-contact (e.g. magnetic) and contact. The contact typ ...