Variable Speed Drives

The efficiency of the induction motor can be improved by controlling the air-gap flux. The flux level varies with load torque i.e. at light load torque the flux required is less than the flux required as the load increases. When the motor is operating at a particular operating point defined by speed and torque, an infinite pair of impressed voltage/frequency can achieve this operating point. However only one particular pair of voltage/frequency will result in the minimum losses and maximum ef ...

A circuit breaker is more reliable for tripping big machines than a drive. Hence some engineers prefer tripping a machine from the breaker via the PLC/safety controller. The machine could be pump or compressor.

After the trip, the startup means energizing the primary side of the transformer, whose secondary side is connected to the variable frequency drive. This subjects the transformer to the startup inrush current which could degrade it.

Tripping the machine may be due ...

Let's look at the question in another light and see if it makes sense.

For some reason, you have access to perhaps 5 separate vehicles - different manufacturers (possibly), different makes and models (almost certainly). You install a dash cam on each vehicle, and wire the cam AND the controls (steering, brakes, accelerator) to a wireless robotic controller that gets its input from a single remote source.

The vehicles are in different parts of the city - or maybe even jus ...

For induction motors if you run the motor at a high flux level the winding flux magnetizing current has a significant third harmonic content that can flow around the Delta winding without appearing in the lines to the VFD.

This is good for the flux waveform but it is not seen by the VFD internal current sensors so you can over-flux and get high motor winding currents giving motor overheating with no indication in the VFD. So with Delta I recommend winding current sensors but this i ...

The Dahlander motor refers to a specific set of optional connections to the main stator winding. These are done OUTSIDE the motor frame (or at least within the main terminal box).

This gives a single pole count for the motor, and the VFD can effectively control the machine as if it were not capable of multiple connections.

The VFD - by itself - cannot "switch" the lead connections to achieve a different pole count. However, it can modify both the applied voltage and freq ...

The main difference between slip ring and cage types is that the slip ring rotor generally has a much lower slip at full speed than the cage rotor if it is properly shorted directly at the rings. We need to check that the variable frequency drive (VFD) slip setting can go low enough. Otherwise only general things need to be considered......mainly the insulation quality of the stator since its likely you are dealing with an older motor.

The slip-ring motor has slightly different imp ...

The most correct term - according to IEEE and IEC - is ASD (Adjustable Speed Drive). This refers to the electronic equipment used to regulate the operating speed of the motor and driven equipment by controlling the frequency and voltage applied to the motor.

NOTE that other terms in common use include (but are not limited to): VSD (Variable Speed Drive), AFD (Adjustable Frequency Drive), and VFD (Variable Frequency Drive), they are referring to the same motor drives, just different ...

Variable frequency drive (VFD) will capable of varying the output speed of a motor without the need for mechanical pulleys, thus reducing the number of mechanical components and overall maintenance. But the biggest advantage that a VFD has is the ability to save the user money through its inherit nature to save energy by consuming only the power that's needed.

A VFD will convert its incoming power, fixed voltage and frequency to variable volta ...

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 ...

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 ...

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 ...

Question: I have a 1.5 kW three phase motor running on a GoHz VFD. The VFD is connected to two phase / 220V supply, the motor is connected in Delta connection. RPM of the motor is 2800 / 3360 at 50 / 60 Hz. It is now running on 50 Hz. I need a RPM of 1400 to 1500 which means I will need to run the motor on 25 Hz which is not a problem with the GoHz VFD. But how much does it affect the motor torque? ...

The beauty of variable frequency drive (VFD) is that the maintenance is negligible if are well maintained.
Yearly maintenance:
Tighten all nuts and bolts, all terminal blocks, cable/wire connections.
Remove dust everywhere (vacuum cleaner is good). Do not try any kind of solvent.
Check all power supply for correct voltage level.
Replace / clean filters.
GoHz maintenance plan do specify which component to change and when (for example blowers every ...

There are 2 different scenarios that occur. One is a circulating current that can occur, mostly through the fact that the rotor is not perfectly formed (you can think of it as not being perfectly round) which creates a circulating current. Insulating one bearing will stop this circulation. The second scenario occurs when a motor is on a VFD (variable frequency drive) and especially a PWM VFD. This produces a charge on the rotor which wants to discharge, and the easiest path is almost always t ...

Question: How can I control through the VFD Torque for a motor as I have a pump motor of 110 KW of rated current 200 A controlled by Soft Starter and during the actual operation it consumed only 65 KW with 98 A, so I want to change this motor with another one lower in KW with VFD to control at the new motor Torque, so could you help me how can I do that?

Answer: If the new motor is large enough to provide the load requirements then reducing the motor ...

VFD and IMO are not going to be competitors in the same market. The benefits of VFD are various depending on the intended use. Bigger the motor (from kW to MW), bigger the benefit. They can act as soft starters therefore reducing the stress caused to the motor during the startup. With the VFD you do not go above nominal current (if you do not want).

VFD for fan and pump applications will considerably increase efficiency of the system as reducing 10% the top speed, the power absorbe ...

First make sure the cause of the noise is not mechanical in nature (bearings, misalignment, worn bearings, lose hardware, lubrication, etc., etc.). If the cause is identified as being electrical in nature you can check some of these.

Is the motor rated for VFD service? Although you may be able to use a regular 3 phase AC motor with some VFD's, a regular 3 phase motor is not design to work with VFD's and thus will operate with higher electrical losses than a motor which is rated for ...

We are looking at an approx 90% + efficiency rating using asynchronous motors with the proper VFD's. With using regen instead of dynamic braking resistors, both in deceleration in traversal motions and in the overhauling effect of the load to the motor in lowering mode, the energy generated by the motor is channeled back to the line source, instead of being dissipated away as heat.
Crane

However, ...

Asynchronous motors are capable of developing significantly higher starting torque than synchronous motors. It has everything to do with the slip. Two pole motors are also an issue at start, due to a significantly lower starting torque capability than 4 or more pole motors.

An encoder of some type is typically used for hoisting applications when the hoist has no mechanical load brake in the gear case. Generally, when we build flux vector hoist controls, we employ 1024 PPR, 24 VDC, ...

For a hoist application
1) You can make a sensorless VFD (variable frequency drive) work on a Hoist however... If an encoder is not used and the VFD doesn't properly sense that there is a problem (it might be a rare occurrence but I've seen it), you could potentially drop the load. It only takes once to seriously damage equipment, hurt someone or worse.
Hoist

2) With an encoder, and proper br ...