Motor peak and continuous current limits - Revision history

Tero K: Text replacement - "\[\[([A-Z]{2,3})\]\]" to "{{param|$1}}"

2015-08-28T19:54:28Z

Text replacement - "\[\[([A-Z]{2,3})\]\]" to "{{param|$1}}"

Tero K: /* Descroption of operation */

2015-02-16T00:11:39Z

‎Descroption of operation

Tero K: /* Descroption of operation */

2014-07-22T12:24:22Z

‎Descroption of operation

Tero K: /* Descroption of operation */

2014-07-22T12:19:23Z

‎Descroption of operation

Tero K: /* I2t motor thermal modeling */

2014-07-22T12:19:15Z

‎I2t motor thermal modeling

Tero K at 12:17, 22 July 2014

2014-07-22T12:17:12Z

Tero K: Created page with "All GD motor drives feature a two stage current limit in order to protect motor and drive from overheating damage. ==Descroption of operation== The basic parameters for curre..."

2014-07-22T11:55:55Z

Created page with "All GD motor drives feature a two stage current limit in order to protect motor and drive from overheating damage. ==Descroption of operation== The basic parameters for curre..."

New page

All GD motor drives feature a two stage current limit in order to protect motor and drive from overheating damage.
==Descroption of operation==
The basic parameters for current limiting are:
*[[MMC]] Motor maximum current a.k.a. motor peak current
*[[MCC]] Motor continuous current a.k.a. motor continuous current
*[[MTC]] Motor thermal constant time
*Peak current time limit ''T'', normally a fixed value of 1 or 2 seconds depending on drive model

[[File:Currentlimits graph.png|800px]]

In ideal case drive would output the demanded current always. However due to the fact that motor and drive generates more heat when current is higher, it is necessary sometimes to reduce output current to a safe level.

* Drive outputs demanded current infinitely if demand is below MCC level
* Drive outputs demanded current if demand is below MMC and time limit T has not been exceeded
* Drive reduces ''T'' based on thermal time constant (MTC) if calculated motor temperature is already at maximum safe level

[[category:Glossary]]

@@ Line 19: / Line 19: @@
 If motor is being driven long enough above continuous current limit, motor temperature will rise to a level where I<sup>2</sup>t will prevent drive from driving current above MCC.
 [[File:Currentlimits graph i2t.png|800px]]
 MTC parameter sets the speed of motor temperature change. Larger motors have greater mass which heats up slowly giving them large thermal time constant while small motors heat up very quickly thus their MTC value is low.

@@ Line 2: / Line 2: @@
 ==Description of operation==
 The basic parameters for current limiting are:
-*[[MMC]] Motor maximum current a.k.a.  motor peak current
+*{{param|MMC}} Motor maximum current a.k.a.  motor peak current
-*[[MCC]] Motor continuous current a.k.a. motor continuous current
+*{{param|MCC}} Motor continuous current a.k.a. motor continuous current
-*[[MTC]] Motor thermal constant time
+*{{param|MTC}} Motor thermal constant time
 *Peak current time limit ''T'', normally a fixed value of 1 or 2 seconds depending on drive model

@@ Line 15: / Line 15: @@
 * Drive outputs demanded current infinitely if demand is below MCC level
 * Drive outputs demanded current if demand is below MMC and time limit T has not been exceeded
-* Drive reduces ''T'' based on thermal time constant (MTC) if calculated motor temperature is already at maximum safe level
+* Drive refuses to drive current above continuous level if I<sup>2</sup> protection estimates motor temperature to be at maximum (see below).
 ==I<sup>2</sup>t motor thermal modeling==

@@ Line 6: / Line 6: @@
 *[[MTC]] Motor thermal constant time
 *Peak current time limit ''T'', normally a fixed value of 1 or 2 seconds depending on drive model
 [[File:Currentlimits graph.png|800px]]
 In ideal case drive would output the demanded current always. However due to the fact that motor and drive generates more heat when current is higher, it is necessary sometimes to reduce output current to a safe level.