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The current drawn at starting (starting current, also called "locked rotor" or "inrush") is directly proportional to the voltage applied at the terminals. This is why soft starters (also called "reduced voltage" starters) are used in the first place.

A reasonable assumption for "standard" squirrel cage induction machines is to assume that the motor will draw somewhere between 7X and 10X the rated line current if started direct-on-line at full rated voltage. As the machine speeds up ...

Case: A fan motor of 315kw running on VFD. Its operating speed is 795 rpm but its winding temperature gets heated like R phase temperature is 126.3 Y phase temperature is 125 and B phase temperature is 120. The motor is surrounded by cooling fans still temperature gets raised. Is there any alternative or have to change the motor to 400kw?

Heating effect can be caused by improper load match of the motor and mechanical VFD. Look at the temperature rise of the motor on the na ...

In really simple terms, there are a couple of factors.

First, the total mass of the induction motor rotor bars must be sufficient to handle the heat generated by the high currents during a transient (start) condition.

Second, the number of induction motor rotor bars (and thus slots) must be slightly different from the number of stator slots to minimize both electromagnetic and acoustic noise.

Third, the number ...

Reactive power is a result of current and voltage waveforms not being "in phase" with each other. If the reactive power is required by the load, the load is considered "lagging" (current lags voltage; load appears as an inductive component). If the load can be over-excited, it can produce reactive power and is referred to as "leading" (current leads voltage;, load appears as a capacitive component).

The only machines ...

All driven loads have some relationship between power and speed. As a general statement - more power is consumed at higher speeds.

Most motors are designed to operate at a constant speed and provide a constant output; however, modern technology requires different speeds in many applications where electric motors are used. A variable frequency drive (VFD) is a device that regulates the speed and rotational force, or output torque of mechanical equipment. Effects of applying VFDs are ...

Most DC systems in vehicles and UPSs are connected to ground (earth) on one pole. Automobiles in the U.S. ground negative. This eliminates high static floating voltages and minimizes arcing when device insulation begins to fail. It also allows a device to be fed with a single wire and use the chassis as a return.

Since an electric substation control system is considered an emergency system, it is not grounded. It is better to burn up a device than to trip off a circuit and disable ...

Basic knowledge of power inverter
Power inverter mainly adopts the PWM at present, controller switch to DC rapidly in a pulse-period to ensure that the DC integral value is equal to the sampling values of AC sine wave at the same time. After filtered, more than 96% sine wave output can be realized. Pulse inverter is self-excited inverter that output voltage is pulse modulation. This kind of power inverter reduces the voltage and electric current pulse number by increasin ...

The soft starter is actually quite a simple device and in many applications, you must use some form of reduced voltage starter to reduce the starting current of the induction motor. If you are compelled to use a reduced voltage starter to reduce electrical disturbances, or to reduce torque transients, then that is a good reason to use a soft starter which complies with these requirements and is stepless and ea ...

Capacitors inside the variable frequency drive (VFD) is mainly used to maintain the DC voltage, this is common thing all are well known about this, but power factor is mainly improved due to the cosine angle between voltage and current are mostly near to each other, however the inductive load produces the reactive power which will directly affect the wave form of input of VFD sine wave when we used additional filter cap ...

Friction losses in motors (AC or DC) are pretty simple when you get right down to it. Basically, any book on the relevant bearing type (sleeve or rolling element) will cover almost everything you need to know.

Induction motors (both squirrel cage and wound rotor) are pretty easy, as they're essentially cylindrical. This means the "friction" developed from moving the rotor through a medium (typically air) is minimal. As the rotor geometry deviates from a true cylinder toward a "fan" ...

When calculating voltage drop please make sure that you are referring to the correct parameters. Don't get confused between voltage drop and voltage difference. Consider a busbar at the source at Voltage Vs and the voltage at the load as Vl. The voltage drop across a line impedance is deltaV and is equal to a vector quantity of the product of current and line impedance. The source voltage is then equal to the load voltage plus the voltage drop across the line added vectorially. The voltage di ...

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 load ...

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 ...