danfoss faq

Frequently Asked Questions For Danfoss Soft Starter Drives

Danfoss 4/6/2018
Frequently Asked Questions For Danfoss Soft Starter DrivesDo Danfoss products comply with RoHS directive (Restriction of Hazardous Substances)?

Yes, all declarations of conformity, including RoHS and WEEE, can be found in our internet product catalogue. Look up the product of your interest and find the relevant document either under the Literature link or the Approvals & Certificates link.

Do you have a soft motor starter for 100 HP?

MCI 50-3 I-O, the biggest soft starter in our CI-tronic range, is for a max. motor power of 40 HP if bypassed during steady state. For even higher rating, we recommend the Danfoss MCD soft starters from the VLT Drives range.

What does “automatic detection of missing phases” mean?

"The MCI can detect if a motor phase (load) or supplying phase is missing. In such situations the two LEDs will flash and the MCI will not activate. It will only detect the phase failure in stand-by mode. The MCI should always be connected to a three-phase motor in order to be operated. "

Can the MCI soft starter be used as a switch or do I need also to install a contactor?

The MCI can be used as a switch, therefore it is not necessary to use an additional contactor. The type of equipment that can be used for operational switching is specified in EN 60364-5. Included here are: contactors and semiconductor devices. It is also specified that not all conductors have to be connected. The conclusion is that a two-phase disconnection by semiconductors is sufficient to meet the requirements in relevant standards for operation of motor loads. Therefore there is no difference between a contactor breaking all three phases mechanically and a semiconductor motor controller like the MCI.

How do I select the correct soft starter?

First you have to keep in mind that a soft starter reduces the starting current. You must select a softstarter which supplies adequate current to ensure smooth operation of the motor or application. Please consider the number of starts per hour and the ambient temperature and also the necessary monitoring and control functions.

Do soft starters have any internal protection?

No, they do not have any protection. You need to use a circuit breaker before the soft starter, or use fuse and contactor with thermal relay, which ensures protection againts overloads and short-circuit.

What is maximum overload current of soft starters?

Maximum overload current for soft starters is 6xIn or 8xIn (where In is nominal current). For more details (duty ratio, number of cycles/hour, time between each start operation) please refer to overload current profile in our technical brochure.

I have a 21 kW motor application with star-delta starter, how can I change to softstarter in the cheapest way?

We recommend the MCI 40 with inside-delta connection.

What is trip class?

Trip class is the expression used in connection with the designation and current settings of overload relays and soft starters. The most popular are 10A and 10 trip classes. They are suitable for light/standard duty applications. Trip class corresponding to minimum overload current withstand time. For example: Class 10A = overload ratio 8 (8 times nominal current) for 1.6 seconds; Class 10 = overload ratio 8 for 3 seconds.

What is the maximum starts and stops of my TCI softstarter?

The TCI softstarter range has unlimited start/stop operations per hour.

Why do we bypass the soft starter in steady state?

Bypass is important when the soft starter is working in temperature above 40 °C – in this case you don't have to reduce load or duty cycle when the soft starter is bypassed in steady state. Moreover bypass eliminates the electromagnetic disturbances EMC during the full voltage operation.

Does the MCI-CH have some protection against phase change?

No, MCI-CH has no phase change detection implemented.

What is the difference between the AC-3 and AC-4 categories?

The AC-3 category is dedicated to squirrel-cage motors; starting, disconnecting while running, whereas AC-4 is dedicated for control of squirrel motors, starting, plugging, inching. When we perform laboratory tests AC-3 means that make current is 6 x In (nominal current), brake current is 1 x In. AC-4: make current 6 x In, brake current 6 x In.