Motor controls
Home » Blog » Motor controls » Control Servo motor with a variable frequency drive

Control Servo motor with a variable frequency drive

Looking at those AC drives they recommend an Induction motor. A servo motor with permanent magnets which is not quite an induction motor. So, if a servo with permanent magnets can be used instead an induction with these kinds of AC drives.

Actually, the term "Servo" makes a reference about "feedback", it means, whether we need a control loop, we are talking in terms about Servo, in this case, we have, or we know, the "feedback" by an encoder. Typical variable frequency drive doesn't have a input for an encoder, so, if you want to control a Servo Motor with a VFD, you can move the motor, but you can't control it.

A servo motor can be an induction servo, a brushless servo, a reluctance servo a dc servo - each of these can be either linear or rotary and can come with a variety of feedback such as tachometer, resolver of various pole counts, incremental or absolute encoders discreet or serial interface with different bus options, laser feedback, halls etc.

Then you come to the term variable frequency drive. Brushless servo amplifiers are also vfds. Do standard inverters have proper control of induction, and brushless motors. Some allow for a software switch, some allow for a firmware download, some don't. Will inverters accept feedback - some have it built in, most that allow it do so by option cards, many do not.

Normal input in a variable frequency drive is, digital to start or stop, and we could have an analogic input to control by potentiometer.

Using AC Drives for the servo application is quite possible, provided the application is less demanding in critical positioning purpose.
There are number of makes that showcases pinpoint positioning of motor shaft being driven by AC Drives like Hitachi SJ700 / Emerson Uni drive SP / Danfoss FC etc.

Its beneficial to opt for the AC Drives as it supports SLVC [ VFD gives almost servo-like torque at low rpms if you give it encoder feedback ], multiple motors can be accessed, torque requirement can be met if required, power dips can be sustained using VFD's.

Post a Comment:

    
Calculate (4 * 4) =

You may also like:

In 3 leg three phase transformer, do we get some phase voltage magnitude and angle change due to un-symmetrical reluctance seen by every different phases? The phase at the middle leg is not distorted because ...
Variable frequency drive is capable to smoothly starting AC motors (ramp from 0 up to 100% of the load) as well as the energy saving will be achieved, accordingly. Also may I confirmed that VFD also acting as ...
Before you attempt to dissipate causative factors of harmonics verbally, you take a look at several studies done by NEMA regarding such, and look into variable frequency drive (VFD) a bit better. You can view ...
For a DC Motor Armature, There is a simple method of determining the condition of the Armature. Drop Test Method: Give a DC Voltage across the commutator Segments for one pole pitch area from a Power supply ...
I am trying to develop a controller for switched reluctance motor which minimizes torque ripple. My design is acquiring torque ripple information from speed signal. In simulation a high pass filter for speed ...
Gozuk Service Gozuk Blog: all about electric motor control & drives industries development in energy saving applications.

Featured

Like pumps, fans consume significant electrical energy while serving several applications. In many plants, the VFDs (variable ... energy consumedA frequency inverter controls AC motor speed. The frequency inverter converts the fixed supply frequency (60 Hz) to a ... Motor starter (also known as soft starter, motor soft starter) is a electronic device integrates soft start, soft stop, ... Soft starter allows the output voltage decreases gradually to achieve soft stop, in order to protect the equipment. Such as the ... Soft Starter reduces electric motor starting current to 2-4 times during motor start up, reduces the impact to power grid during ...

In Discussion