Apparatus and means for starting of AC motors, algorithm for self-adapting motor start with soft-starter

Patent metadata

Field	Value
Publication number	US-9742316-B2
Application number	US-201514693165-A
Country	US
Kind code	B2
Filing date	Apr 22, 2015
Priority date	Apr 23, 2014
Publication date	Aug 22, 2017
Grant date	Aug 22, 2017

Abstract

The invention relates to a method of starting an electric motor ( 10 ) powered by an alternating power supply voltage, said method consisting of supplying current to the motor ( 10 ) with a delay t ret , during each period of the power supply voltage. The starting method comprises a first sequence in which the following steps are carried out during each n th period of the power supply voltage, where n is an integer number greater than 0: a) determine the value of a variation of a resistance of the electric motor during the previous n periods of the power supply voltage; b) compare said value of the variation of the determined motor resistance with a first threshold resistance value; c) if the value of the variation of the motor resistance is less than the first threshold value, reduce t ret . The invention also relates to a starter device and a computer program.

First claim

The invention claimed is:

1. A starting method for an electric motor powered by an alternating power supply voltage of an alternating power supply circuit, the starting method, comprising:
supplying current to the electric motor during each voltage supply period with a delay t ret ; and
performing a first sequence in which the following steps are carried out in each n th period of the alternating power supply voltage, where n is an integer number greater than 0, including:
first determining a value of a variation of an electric motor resistance during a previous n periods of the alternating power supply voltage,
first comparing the determined value of the variation of the electric motor resistance with a first threshold resistance value, and
if the value of the determined value of the variation of the electric motor resistance is less than the first threshold value, first reducing the delay t ret ,

wherein the first sequence includes the following additional step:
if the value of the determined value of the variation of the electric motor resistance is equal to or greater than the first threshold value, proceeding onto a second sequence in the starting method, the second sequence comprising following steps performed every m th period of the alternating power supply voltage, where m is an integer more than 0, including:
second determining the value of the variation of the electric motor resistance,
second comparing the determined value of the variation of the electric motor resistance with a second threshold resistance value, and
if the variation in the determined value of the variation of the electric motor resistance is less than that the second threshold resistance value, second reducing t ret .

2. The starting method according to claim 1 , wherein the first determining is a step to determine a relative variation in time of the electric motor resistance

Δ
⁢

⁢
R

R

⁢

(
t
)

Δ
⁢

⁢
t

.

3. The starting method according to claim 2 , wherein the relative variation in time of the electric motor resistance is calculated using the following equation:

Δ
⁢

⁢
R

R

⁢

(
t
)

Δ
⁢

⁢
t

=

R
⁡

(
t
)

-

R
⁡

(

t
-
nT

)

R
⁡

(

t
-
nT

)

nT

where R(t) is a value related to the electric motor resistance determined at instant t and T is a duration of a period of the alternating power supply voltage.

4. The starting method according to claim 1 , wherein first determining, first comparing, and first reducing are applied after an initial duration t int 1 .

5. The starting method according to claim 1 , wherein after a reduction in the delay t ret , the first sequence is repeated after a waiting time t int 2 .

6. The starting method according to claim 1 , wherein during the second determining, an acceleration or speed of the electric motor is also determined from the determined value of the variation of the electric motor resistance.

7. The starting method according to claim 1 , wherein in the second determining, the determined value of variation of the electric motor resistance is a value corrected over at least two periods of the alternating power supply voltage.

8. The starting method according to claim 1 , wherein the second comparing is a step to determine the value of the relative variation of the electric motor resistance in time.

9. The starting method according to claim 8 , wherein the value of the relative variation of the electric motor resistance in time is calculated using the following equation:

Δ
⁢

⁢
R

R

⁢

(
t
)

Δ
⁢

⁢
t

=

R
⁡

(
t
)

-

R
⁡

(

t
-
mT

)

R
⁡

(

t
-
mT

)

mT

where

Assignees

• Schneider Electric Ind Sas

Inventors

• Durand Christophe
• Penkov Delcho

Classifications

• H02P1/28 Primary

  by progressive increase of voltage applied to primary circuit of motor · CPC title

• H02P1/04 Primary

  Means for controlling progress of starting sequence in dependence upon time or upon current, speed, or other motor parameter · CPC title