如何选择合适规格的软启动器？

软启动器的选型需根据所连接电机的启动工况要求来确定。相关因素包括：

• 启动电流（取决于设备类型）

• 启动持续时间（取决于设备类型）

• 启动频率（取决于工艺流程）

• 环境温度

How do I select the right size soft starter?

Soft starters need to be sized according to the required start duty for the connected motor. Factors include

• Start current (depends on machine type)

• Start duration (depends on machine type)

• Start frequency (depends on the process)

• Ambient temperature

什么是 AC53 使用类别代码？

AC53a 使用类别代码定义了非旁路型软起动器的额定电流及标准运行条件。

软起动器的额定电流决定了其所能配套使用的最大电机规格。该额定值取决于每小时起动次数、起动持续时间与电流水平，以及软起动器在运行周期内实际工作（即有电流通过）的时间比例。

软起动器的额定电流仅在符合 AC53a 代码规定的条件下有效；在不同的运行条件下，其额定电流可能会有所增减。

AC53b 使用类别代码定义了旁路型软起动器（包括内置旁路或安装了外部旁路接触器的类型）的额定电流及标准运行条件。

软起动器的额定电流决定了其所能配套使用的最大电机规格。该额定值取决于每小时起动次数、起动持续时间与电流水平，以及两次起动之间软起动器处于停止状态（无电流通过）的时间长短。

软起动器的额定电流仅在符合 AC53b 代码规定的条件下有效；在不同的运行条件下，其额定电流可能会有所增减。

What are AC53 Utilisation Codes?

The AC53a Utilisation Code defines the current rating and standard operating conditions for a non-bypassed soft starter.

The soft starter’s current rating determines the maximum motor size it can be used with. The soft starter’s rating depends on the number of starts per hour, the length and current level of the start, and the percentage of the operating cycle that the soft starter will be running (passing current).

The soft starter’s current rating is only valid when used within the conditions specified in the AC53a code - the soft starter may have a higher or lower current rating in different operating conditions.

The AC53b Utilisation Code defines the current rating and standard operating conditions for a bypassed soft starter (internally bypassed, or installed with an external bypass contactor).

The soft starter’s current rating determines the maximum motor size it can be used with. The soft starter’s rating depends on the number of starts per hour, the length and current level of the start, and the amount of time the soft starter will be off (not passing current) between starts.

The soft starter’s current rating is only valid when used in the conditions specified in the AC53b code - the soft starter may have a higher or lower current rating in different operating conditions.

软启动与初级电阻启动有何区别？

与初级电阻启动器相比，软启动器更具灵活性和可靠性。

初级电阻启动器的性能存在局限，原因如下：

• 无法精确调节启动转矩以匹配电机和负载特性。

• 在每个电压切换档位都会产生电流和转矩的瞬态波动。

• 设备体积大且成本高。

• 液体电阻式启动器需要频繁维护。

• 启动性能会随电阻发热而变化，因此难以有效控制连续启动或重复启动的情况。

• 无法适应变化的负载工况（例如带载启动或空载启动）。

• 无法实现软停止功能。

Difference between Soft Starting and Primary Resistance Starting?

Compared with primary resistance starters, soft starters are more flexible and reliable.

Primary resistance starters offer limited performance because:

• Start torque cannot be fine-tuned to match motor and load characteristics.

• Current and torque transients occur at each voltage step.

• They are large and expensive.

• Liquid resistance versions require frequent maintenance.

• Start performance changes as the resistance heats up, so multiple or restart situation are not well controlled.

• They cannot accommodate changing load conditions (eg loaded or unloaded starts).

• They cannot provide soft stop.

什么是“内三角”接法？

内三角接法（也称为六线接法）将软启动器的晶闸管（SCR）与电机的每个绕组串联连接。这意味着软启动器仅承载相电流，而非线电流。这使得软启动器能够控制满载电流超过其常规额定值的电机。

采用内三角接法时，必须同时配备主接触器或带分励脱扣功能的塑壳断路器（MCCB），以便在发生跳闸时将电机和软启动器与电源断开。

内三角接法：

• 简化了星三角启动器的更换过程，因为可以利用现有的接线。

• 可能降低安装成本。虽然软启动器本身的成本会降低，但会产生额外的电缆和主接触器费用。因此，需要针对具体情况进行成本核算。

只有当电机的三个绕组的每一端都能单独引出并进行连接时，才可以使用内三角接法来控制该电机。

并非所有软启动器都支持内三角接法。

What is inside Delta connection?

Inside delta connection (also called six-wire connection) places the soft starter SCRs in series with each motor winding. This means that the soft starter carries only phase current, not line current. This allows the soft starter to control a motor of larger than normal full load current.

When using an inside delta connection, a main contactor or shunt trip MCCB must also be used to disconnect the motor and soft starter from the supply in the event of a trip.

Inside delta connection:

• Simplifies replacement of star/delta starters because the existing wiring can be used.

• May reduce installation cost. Soft starter cost will be reduced but there are additional cabling and main contactor costs. The cost equation must be considered on an individual basis.

Only motors that allow each end of all three motor windings to be connected separately can be controlled using the inside delta connection method.

Not all soft starters can be connected in inside delta.

需要旁路接触器吗？

当电机全速运行时，旁路接触器会将软启动器的晶闸管（SCR）旁路（即短接）。这样可以消除运行期间晶闸管产生的热损耗。

有些软启动器内置了旁路接触器，而另一些则需要外接旁路接触器。

旁路接触器的作用：

• 允许将软启动器安装在密封机柜内

• 省去机柜强制通风系统的成本

• 通过消除运行期间的晶闸管损耗来节能

旁路接触器的 AC1 额定电流应与电机的满载电流（FLC）相匹配。采用 AC1 额定值是合适的，因为旁路接触器既不承载启动电流，也不负责切断故障电流。

Do I need a bypass contactor?

Bypass contactors bridge out a soft starter’s SCRs when the motor is running at full speed. This eliminates heat dissipation from the SCRs during run state.

Some soft starters include built-in bypass contactors, others require an external bypass contactor.

Bypass contactors:

• Allow soft starters to be installed in sealed enclosures

• Eliminate the cost of forced-air cabinet ventilation

• Save energy by eliminating SCR losses during run

Bypass contactors should be AC1 rated for the motor FLC. The AC1 rating is adequate because the bypass contactor does not carry start current or switch fault current.

软启动器可以配合功率因数校正（PFC）使用吗？

当电机全速运行时，旁路接触器会跨接并旁路软启动器的晶闸管（SCR），从而消除运行期间晶闸管产生的热损耗。

部分软启动器内置了旁路接触器，而另一些则需要外接旁路接触器。

PFC 电容器的容量可根据以下公式计算：

kVA (电容器) = √3 × 线电压 × 0.8 × 电机空载电流

Can I use power factor correction with a soft starter?

Bypass contactors bridge out a soft starter’s SCRs when the motor is running at full speed. This eliminates heat dissipation from the SCRs during run state.

Some soft starters include built-in bypass contactors, others require an external bypass contactor.

PFC capacitors can be sized using the following formula:

kVA (Cap) = √3 x Vline x 0.8 x motor no load current

如何确保实现1类（Type 1）电路保护？

1 类保护的要求是：当软启动器输出端发生短路时，必须切除故障，且不得对人员造成伤害风险。该标准并不要求软启动器在故障排除后仍能继续运行。

1 类保护通常由作为电机分支电路一部分的 HRC 熔断器或塑壳断路器（MCCB）来实现。

该保护方案至少必须能够承受电机启动时所需的电流。

UL 和 IEC 标准中规定了用于电机 1 类保护的熔断器最大额定值。

How do I ensure Type 1 circuit protection?

Type 1 protection requires that, in the event of a short circuit on the output of a soft starter, the fault must be cleared without risk of injury to personnel. There is no requirement that the soft starter must remain operational after the fault.

Type 1 protection is provided by HRC fuses or a MCCB that form part of the motor branch circuit.

As a minimum, the protection method must be able to sustain the required motor start current.

Maximum fuse ratings for Type 1 motor protection are specified in UL and IEC standards.

如何确保实现2类（Type 2）电路保护？

2类保护要求：当软启动器输出端发生短路时，必须能够切除故障，且不危及人员安全或损坏软启动器。

实现2类保护需使用半导体熔断器。此类熔断器必须能够承载电机启动电流，且其总切断 I²t 值必须小于软启动器内部晶闸管（SCR）的 I²t 值。

用于2类电路保护的半导体熔断器，是电机支路保护配置中 HRC 熔断器或塑壳断路器（MCCB）之外的附加保护元件。

How do I ensure Type 2 circuit protection?

Type 2 protection requires that in the event of a short circuit on the output of a soft starter the fault must be cleared without risk of injury to personnel or damage to the soft starter.

Type 2 protection is achieved by using semiconductor fuses. These fuses must be able to carry motor start current and have a total clearing I2t < the I2t of the soft starter SCRs.

Semiconductor fuses for Type 2 circuit protection are additional to HRC fuses or MCCBs that form part of the motor branch circuit protection.

软启动器与电机之间的电缆敷设最大长度是多少？

软启动器与电机之间的最大距离取决于电压降和电缆电容。

当电机满载运行时，电机端子处的电压降不得超过当地电气法规规定的限值；电缆选型应据此进行。

对于超过 500 米的电缆敷设，电缆电容可能成为一个影响因素。

What is the maximum length of cable run between soft starters and the motor?

The maximum distance between the starter and motor is determined by the voltage drop and the cable capacitance.

Voltage drop at the motor terminals must not exceed the limit specified in local electrical regulations when the motor is running fully loaded. Cabling should be sized accordingly.

Cable capacitance can be a factor for cable runs that are longer than 500 metres.

绕线转子电动机可以使用软启动器启动吗？

可以，前提是电动机在新的配置下所能提供的转矩足以带动负载加速。这一点可能难以确定，或许需要进行试验。

软启动不适用于以下应用场景：

• 绕线转子电动机的安装目的是为了实现调速控制。

• 负载需要极高的启动转矩。

为了产生启动转矩，电动机在启动过程中必须在转子回路中保留一定的电阻。当电动机运行至接近全速时，必须使用接触器（额定等级为 AC2，适用于转子电流）将该电阻短接切除。

R（每相）= 0.2 x (VR / √3 x IR)

转子电阻 (R) 可通过以下公式计算：

其中 VR = 转子开路电压

IR = 转子满载电流

功率（每相）= (20% x 电动机功率 kW) / 3

其中 VR = 转子开路电压

IR = 转子满载电流

Can a slip ring motor be started with a Soft Starter?

Yes, provided that the torque available from the motor under the new configuration is sufficient to accelerate the load. This may be difficult to determine and a trial may be required.

Soft starting is not suitable for applications where:

• the slip-ring motor was installed to deliver speed control.

• the load requires extreme start torque.

To develop starting torque, some resistance must remain in the rotor circuit during motor starting. This resistance must be bridged out using a contactor (AC2 rated for rotor current) once the motor is running close to full speed.

R (per phase) = 0.2 x (VR / √3 x IR )

Rotor resistance (R) can be sized using the following formula:

Where VR= open circuit rotor voltage

IR= full load rotor current

Power (per phase) = (20% x motor kW) / 3

Where VR= open circuit rotor voltage

IR = full load rotor current

可以将软启动器用于双速电机吗？

软启动器适用于两种最常见的双速电机。在这两种情况下，都必须针对低速和高速运行分别提供电机保护。

Dahlander电机是一种专用电机，常用于双速压缩机或风机应用。该电机的绕组通过外部接触器进行配置，以实现高速（双星形）和低速（三角形）运行。

双绕组电机在同一转轴上具有两种独立的极数配置（例如 4 极/8 极）。每种极数配置（即速度）均通过外部 AC3 等级的接触器进行选择。

PAM（极幅调制）电机通过外部绕组配置有效改变定子频率来调节速度。软启动器不适用于此类双速电机。

Can I use a soft starter with a two-speed motor?

Soft starters can be applied to the two most common types of two-speed motor. In both cases, separate motor protection must be provided for low and high speed operation.

Dahlander motors are special purpose motors often applied to two-speed compressor or fan applications. The motor windings are externally configured using contactors for high speed (dual star) and low speed (delta) operation.

Dual-winding motors have two separate pole configurations (eg 4 pole / 8 pole) on a common shaft. Each pole configuration (speed) is selected using an external AC3 rated contactor.

PAM (Pole Amplitude Modulated) motors alter the speed by effectively changing the stator frequency using external winding configuration. Soft starters are not suitable for use with this type of two-speed motor.

一台软启动器能否分别控制多台电机进行顺序启动？

可以，一台软启动器能够按顺序控制两台电机。然而，这种方案的控制与接线既复杂又昂贵；软启动器本身节省的成本，往往会被额外的元件费用和人工成本所抵消。

若要在顺序启动场景中使用软启动器，需满足以下条件：

1. 每台电机都必须配备独立的主接触器、旁路接触器和过载保护装置。

2. 软启动器的额定参数必须能够满足总启动负载的要求。

Can one soft starter control multiple motors separately for sequential starting?

Yes, one soft starter can control two motors in sequence. However, the control and wiring is complex and expensive and any saving in soft starter cost is often outweighed by additional component and labour costs.

In order to use a soft starter in a sequential starting situation:

1. Each motor must have a separate main contactor, bypass contactor and overload protection

2. The soft starter must be suitably rated for the total start duty.

软启动器可以控制多台电机进行并联启动吗？

可以。具体的电路配置和软启动器选型取决于应用场景。

每台电机都必须配备独立的过载保护装置。

如果电机规格相同且在机械上相互耦合（刚性连接），则可以使用恒流型软启动器。

如果电机规格不同，和/或负载在机械上未相互联锁，则应使用具备定时电压斜坡（TVR）启动特性的软启动器。

所有电机的满载电流（FLC）之和不得超过软启动器的额定满载电流。

Can one soft starter control multiple motors for parallel starting?

Yes. The circuit configuration and soft starter selection depends on the application.

Each motor must have its own overload protection.

If the motors are the same size and are mechanically coupled, a constant current soft starter can be used.

If the motors are different sizes and/or the loads are not mechanically interlocked, a soft starter with a timed voltage ramp (TVR) start profile should be used.

The combined motor FLCs must not exceed the soft starter FLC.

软启动器能改变电机的转向吗？

软启动器本身无法让电机以全速反向运行。不过，通过配置正反转接触器，可以实现电机的正反转运行。

某些软启动器也具备“部分速度”功能，无需反转接触器即可让电机以低速正向或反向运行。但这种反转运行仅限于以固定的低速短时间进行。

Can soft starters reverse the motor direction?

On their own, soft starters cannot run motors in reverse direction at full speed. However, forward and reverse operation can be achieved by using a forward and reverse contactor arrangement.

Some soft starters also provide a part speed function that runs the motor at slow speed in either forward or reverse, without a reversing contactor. However, reverse operation is limited to short periods at a fixed slow speed.

什么是直流（DC）制动？它是如何工作的？

直流制动利用直流注入来实现电动机减速。

当软起动器接收到停止指令时，它会先将电动机减速至全速的约 70%。随后，起动器施加最大制动转矩，使电动机在设定的时间内停止运转。

与软制动相比，直流制动具有以下特点：

• 无需使用直流制动接触器。

• 控制所有三相电路，从而使制动电流及由此产生的热量在电动机内部均匀分布。

What is DC Braking and how is it used?

DC braking uses DC injection to slow the motor.

When the soft starter receives a stop command, it slows the motor to approximately 70% of full speed. The starter then applies maximum brake torque to stop the motor in the programmed time.

Compared with soft braking, DC braking:

• Does not require the use of a DC brake contactor

• Controls all three phases so that the braking currents and associated heating is evenly distributed through the motor.

什么是软制动？它是如何工作的？

软制动是软启动器用于缩短电机停机时间的两种技术之一；另一种技术是直流（DC）制动。

软制动利用安装在软启动器输入端的换向接触器来实现。当软启动器接收到停机指令时，它会控制换向接触器动作，使电机以反向运行的方式进行“软启动”。这一过程会对负载施加制动转矩。

与直流制动相比，软制动具有以下特点：

• 引起的电机发热较少

• 在相同电流下能提供更大的制动转矩

软制动更适用于具有极高惯性的负载。

What is Soft Braking and how is it used?

Soft braking is one of two techniques used by soft starters to shorten motor stopping time. The other technique is DC braking.

Soft braking uses reversing contactors on the input of the soft starter. When the soft starter receives a stop command, it operates the reversing contactors and the motor is effectively soft started in the reverse direction. This applies a braking torque to the load.

Compared to DC braking, soft braking:

• Causes less motor heating

• Provides more braking torque for a given current

Soft braking is better for extremely high inertia loads

使用软启动器时的最小启动电流是多少？

软启动器可以将启动电流限制在任意所需水平。然而，确保成功启动所需的最小启动电流取决于具体的电机和负载。

若要成功启动，电机在整个启动过程中产生的加速转矩必须大于负载所需的转矩。

降低启动电流的同时，电机产生的转矩也会随之降低。启动电流的降低限度在于：输出转矩必须始终保持略大于负载所需的转矩。

虽然可以根据经验估算可能的启动电流，但若要进行更精确的预测，则需要分析电机和负载的转速-转矩特性曲线。

成功启动：

启动失败：

What is the minimum start current with a soft starter?

Soft starters can limit start current to any desired level. However, the minimum level of start current for a successful start depends on the motor and load.

To start successfully, the motor must produce more acceleration torque than the load requires, throughout the start.

Reducing the start current also reduces the torque produced by the motor. The start current can only be lowered to the point where the torque output remains just greater than the load torque requirement.

The likely start current can be estimated from experience, but more precise predictions require analysis of motor and load speed/torque curves.

Successful start:

Unsuccessful start:

软启动器能否控制已经在旋转的电机（即“飞车”负载）？

可以，软启动器能够启动已经在旋转的电机。

通常情况下，电机正向旋转的速度越快，启动所需的时间就越短。

如果电机处于反向旋转状态，软启动器会先将其减速至静止，然后再加速至正向运行。在选型时，请务必考虑这种情况下延长的启动时间。

无需特殊的接线或软启动器设置。

Can soft starters control an already rotating motor (flying load)

Yes, soft starters can start motors that are already rotating.

In general, the faster the motor is rotating in the forward direction, the shorter the start time will be.

If the motor is rotating in the reverse direction, it will be slowed to a standstill and then accelerate forwards. Allow for the extended start time when rating the soft starter.

No special wiring or soft starter setup is required.

所有的三相软启动器都一样吗？

不，软启动器有多种类型，它们控制电机的方式各异，功能也各不相同。

1. 单相控制

此类设备可减轻启动时的转矩冲击，但无法降低启动电流。它们也被称为转矩控制器，必须与直接在线启动器配合使用。

2. 两相控制

此类设备可消除转矩瞬变并降低电机启动电流。在电机启动过程中，未受控相的电流会略高于受控的两相。它们适用于除重载工况以外的各种应用场景。

3. 三相控制

此类设备对三相均进行控制，可提供最佳的软启动控制效果。在重载启动工况下，应采用三相控制方式。

Are all three phase soft starters the same?

No. There are different styles of soft starter which control the motor in different ways and offer different features.

1. Single Phase Control

These devices reduce torque shock at start but do not reduce start current. Also known as torque controllers, these devices must be used in conjunction with a direct on-line starter.

2. Two Phase Control

These devices eliminate torque transients and reduce motor start current. The uncontrolled phase has slightly higher current than the two controlled phases during motor starting. They are suitable for all but severe loads.

3. Three Phase Control

These devices control all three phases, providing the optimum in soft start control. Three phase control should be used for severe starting situations.