GB/T 37404-2019 English PDF (GBT37404-2019)

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GB/T 37404-2019: Application guide of soft-start device for high-voltage motor
GB/T 37404-2019
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 29.200
K 46
Application guide of soft-start device for high-voltage
motor
ISSUED ON: MAY 10, 2019
IMPLEMENTED ON: DECEMBER 01, 2019
Issued by: State Administration for Market Regulation;
Standardization Administration of the People's Republic of
China.
Table of Contents
Foreword ... 3 
1 Scope ... 4 
2 Normative references ... 4 
3 Terms and definitions ... 4 
4 Classification ... 5 
5 Type selection calculation ... 5 
6 Starting schemes ... 8 
7 Bypass ... 12 
Application guide of soft-start device for high-voltage
motor
1 Scope
This Standard specifies terms and definitions, classification, parameters
required for type selection calculation, starting scheme, bypass of soft-start
device for high-voltage motor (hereinafter referred to as the “soft-start device”).
This Standard is applicable to the soft-start device of which the rated working
voltage is 3kV~10kV, the input frequency is 50Hz or 60Hz.
2 Normative references
The following referenced documents are indispensable for the application of
this document. For dated references, only the edition cited applies. For undated
references, the latest edition of the referenced document (including any
amendments) applies.
GB/T 33595-2017, Motor soft-start device - Method of type designation
GB/T 33984-2017, Motor soft-start device - Terminology
GB 50217-2018, Standard for design of cables of electric power engineering
3 Terms and definitions
For the purposes of this document, the terms and definitions defined in GB/T
33984-2017 as well as the followings apply.
3.1 bypass
A process that closes the short-circuit switch connected in parallel with the soft-
start device so that no current flows through the soft-start device.
3.2 bypass switch
A switch that conducts the bypass, which short-circuits the soft-start device and
the soft-start circuit during the bypass process.
● rated current;
● rated voltage;
● rated power;
● rated speed;
● moment of inertia;
● torque-speed curve or stall torque multiple at rated voltage;
● current-speed curve or stall current multiple at rated voltage.
- Load parameters:
● moment of inertia / flywheel moment;
● static resistance torque;
● resistance torque-speed curve that is converted to the motor end.
- Power grid parameters:
● grid short-circuit capacity or short-circuit impedance;
● length and specification of incoming cable or overhead line.
- Environmental conditions:
● altitude;
● relative humidity;
● ambient temperature;
● pollution level.
- Process requirements:
● start frequency.
When the relevant parameters change, it shall recalculate the calculation
results of the type selection.
5.2 Performance indicators
The parameter indicators that are specified by users and in accordance with
national grid regulations, include:
- pilot differential protection (optional);
- open triangle voltage protection (optional).
NOTE: The setting values of current quick-break protection and over-current protection
shall consider the characteristics of the soft-start device.
5.5 Matching type selection
5.5.1 Cable
The type selection of cable shall meet the requirements of GB 50217-2018.
Under the premise that the cable temperature rise is met in the starting circuit,
the capacity can be reduced.
When it uses a high-voltage variable-frequency soft-start device and when the
output side is connected to the motor at a long distance, it is advisable to
calculate the damage to the motor caused by the voltage spikes generated by
the output harmonics.
5.5.2 Switch
It shall select the breaking capacity of corresponding switch according to the
short-circuit capacity of the power grid. The starting circuit shall choose a switch
of the appropriate current level according to the starting current ratio. The
bypass circuit shall select a switch of the appropriate current level according to
the motor rated current.
5.6 Loss
Due to the short-term operation of the soft-start device, it is unnecessary for the
soft-start device manufacturer to calculate the loss.
6 Starting schemes
6.1 Typical scheme of motor stator to side-connect soft-start device
6.1.1 One-for-one system scheme
The one-for-one system scheme is shown as Figure 1.
3 - Bypass switch (contactor or circuit breaker);
4 - Starting circuit switch (contactor or circuit breaker);
5 - Soft-start device.
Figure 3 -- Typical scheme of motor rotor to side-connect soft-start
device
Connect the soft-start device to the rotor side of the motor. After the soft-start
device and the process are ready, the signal shall be sent to the central control
system. The central control system shall send the well-preparation signal. The
power incoming switch shall be closed. After the site or the central system
sends a command, the starting and operation switches 2 and 4 shall be closed
and the soft-start device shall be put into operation. After the soft-start device
detects that the motor meets the bypass conditions, the bypass switch shall
close, starting and operation switch 4 shall be disconnected, the soft-start
device shall stop operating and the starting shall be completed.
When the back-end circuit of the starting and operating switch is short-circuited,
it shall have the ability to interrupt the short-circuit current.
7 Bypass
7.1 Overview
After the motor is driven by the soft-start device to near the rated speed, it shall
be connected to the grid for direct power operation.
7.2 Bypass requirements for buck soft-start
Before bypassing, the soft-start device shall, through a direct or indirect manner,
detect the amplitudes of motor speed and motor terminal voltage. When it is
determined that the amplitudes of motor speed and motor terminal voltage meet
the design requirements, the soft-start device shall give bypass instruction. The
specific requirements are determined by the manufacturer and user according
to the site conditions.
7.3 Bypass requirements for variable-frequency soft start
Before bypassing, the soft-start device shall, through a direct or indirect manner,
detect the amplitudes, phases and frequencies of motor speed and motor
terminal voltage. When it is determined that the amplitudes, phases and
frequencies of motor speed and motor terminal voltage meet the design
requirements, the soft-start device shall give bypass instruction. The specific
requirements are determined by the manufacturer and user according to the