Efficiency: 0,8 for a motor < 5KW
Efficiency: 0,9 for a motor > 5KW
Power factor: 0,8 for a motor < 5KW
Power factor: 0,9 for a motor > 5KW
V3 = 1,732
Nominal current absorbed by the motor:
I = 1500 = 26,7 A
400 x 1,732 x 0,9 x 0,9
The current rating of the relay must be 4 x I of the motor in order to withstand starting currents:
>>> 106,8 A >>> it's necessary to take a 125 A relay.
Because of their semiconductor technology-based design, SSRs provide a higher degree of reliability, longer life and reduced electromagnetic interference (EMI), as well as faster response times and vibration and shock resistance, when compared to the EMR counterparts. This is due to the fact that SSRs have no mechanical contacts to wear out or arc, which is the primary cause for EMR failure.
A curve without heatsink is given for the SO/SC or SG type of solid state relays.
When mounted on the back plate of a cabinet, the relay/plate contact must be correct.
An aluminium back plate of 150mm x 150mm x 3 mm corresponds to approximately 4°/W
An aluminium back plate of 300mm x 300mm x 3 mm corresponds to approximately 2°/W
In all cases, it is recommended to perform a test and measure the heat dissipation.
A steel plate will have greater thermal resistance.
Problems from the mains:
The relay will only turn on when the mains (output) voltage is near zero.
When the control voltage is on the relay will switch on at the same moment, whatever the mains voltage value.
Zero-cross relays are used with resistive loads while random turn-on relays are used with inductive loads (motors, transformers, coils etc.).
This happens mainly with zero-cross SSR with DC control: the input signal is rectified but not filtered: at zero-cross input signal is too low to make a valid control signal.
Solution: put a capacitor across the input
Check if there is a connection between terminals 5 & 6
This is not possible because of the technology used. In fact current will always go through one SSR only
This is possible but you should respect some conditions:
It's reasonable to use 2 or 3 single phase relays. Our SGT/SVT 75, 95, and 125A are used for loads with non permanent peak current (as lamps, motors...), or to have a better protection.
Altitude affects insulation and heat dissipation, both get lower as altitude grows.
Heat dissipation will get worse, so it might be necessary to increase the size of the cooling element (heat sink) used with the SSR. Tests must be done at nominal current and ambient temperature with T°C measurement on the heat sink close to the relay. Temperature should not get over 100 °C.
There are several ways to ensure grounding of SSR assemblies:
- Solid State Relays have a protective earth connection ; or
- Their construction ensures a good connection to its fixing mean (Din rail, plate, panel,...) having themself a protective earth connection.
For more detailed information.