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Need help selecing a motor soft start? We'll break it down for you.

Motor Soft Start Selection

Motor Types

Both AC and DC motors, as well as single and three phase motors, can use a motor soft start.

AC Motor Soft Start

Sizing a Motor Soft Start

A motor's power requirements are measured in current, voltage, kilowatts and horsepower. The bigger the motor the larger the soft starter that will be required.

Protecting a Motor Soft Start From Environmental Conditions

The number of starts and the environmental conditions also have to be taken into account when selecting a soft starter. Environmental conditions, such as ambient temperature, humidity, and altitude, can shorten the life of the starter.

For example, if the soft starter is being used in a hot environment, then the soft start needs to be derated to allow for proper operation. In some cases, corrosive gases and acids may exist that can also damage the motor and starter.

To give the motor extra defense from external conditions, circuit boards should be given an extra protective coating.

How Often Can I Turn On The Motor Soft Start?

The number of starts per hour that a soft starter is limited to is dependent upon the following:

The soft starter being used will also be a factor, with the starts per hour varying by model.

Can a motor soft starter be used to adjust motor starting duration and current?

Start ramp is how long it will take for a soft starter to reach full voltage. This parameter can be controlled with a soft starter. If the ramp time is too long, it can result in the overheating of the motor and increase the risk of the overload relay tripping.

The duration of the start time for the motor will depend on the size of the load the motor is carrying: if the motor is unloaded, the ramp time will be shorter, but if the motor is heavily loaded, the ramp time will become longer.

Some starters have a control function through which current draw is limited to a set value during voltage ramp up or ramp down period. Stop ramps may also be programmed into the starter. They are used when soft stopping is required.

Motor Soft Start Programming

A solid state starter will be digital, which means it can be programmed to reach a certain voltage in a set amount of time or limit current to a set value during startup. These starters will contain a number of communications features for interacting with other devices to suit your needs.

Some common connection types include ethernet, ModBus RS232.485, analog and discrete triggered input terminals.

What is a kickstarter?

Soft starters may have a kickstarter function, which can provide an extra pulse of torque if necessary.

Kickstarters are useful in cases where high-friction loads are encountered and a momentary boost of power is needed for starting the motor.

For example, a jammed conveyor belt or pump. The extra boost of torque may clear the jam and allow the machine to resume operation.

Motor Soft Start Kickstarter

Can A Motor Soft Start Run Multiple Motors At Once?

If each motor has separate circuit protection, then a starter can run multiple motors at once.

Parallel start of motors: The soft starter must be able to handle the combined full load and starting current for all motors.

Sequential start of motors: The soft starter must be able to handle the starting current of each motor.

Where Can I Buy My Motor Soft Start?

View our motor soft start selection online here. If you have any questions or wish to place an order by phone, call us at 510.490.2187.

Call us at 877.474.8209 to speak with an application engineer about your project.